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Clinical Foundations Course > Applied Pharmacology > Flashcards

Applied Pharmacology Flashcards

1
Q

Describe the body compartements in terms of drug distribution.

A
  • Central
    • Venous
  • Peripheral
    • Skeletal muscle
  • Deep
    • Fat or nervous tissue
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2
Q

Describe the pharcacokinetics of the two compartment open model, first order elimination pharmacokinetics.

A

Drug will be eliminated at a high rate when in the central compartment (the compartement in which it can be eliminated from). As the drug reaches an equilibrium concentration with the peripheral compartment, the elimination of the drug will occur at a slower rate.

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3
Q

What is ion trapping?

A

A molecule can be trapped in a particular body compartment or part of the body because of changes in solubility with ionization

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4
Q

Describe the Henderson-Hassleback equation for acids and bases.

A
  • For acids
    • pH-pKa = log [ionized/non-ionized]
  • For bases
    • pH-pKa = log [non-ionized/ionized]
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5
Q

What is the pKa?

A

The pH at which a 50% of a drug is ionized.

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6
Q

What factors must be taken into account when using a veterinary oral drug?

A
  • Ease of administration (animal behavioural factors)
  • Taste of the drug
  • Interactions drug will have with gastrointestinal environement (food and acidic conditions of the stomach)
  • Speed of gastric emptying
  • First pass effect: removal of a percentage of the drug as it passes through the liver via the portal circulation before it reaches the systemic circulation
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7
Q

How can one quantify the a drug’s total exposure in an individual.

A

Indicated by the area under the drug concentration in the body versus time curve.

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8
Q

What does the area under the plasma drug concentration versus time curve (AUC) help quantify?

A
  • Indication of total exposure to the drug
  • Used to define bioavailability
  • Used to calculate clearance of the drug
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9
Q

Describe certain’s drugs’ interaction with plasma proteins and why this is important.

A
  • Certain drugs reversibly bind highly to plasma proteins (albumin protein, for example)
    • Bound drugs do not move across membranes
    • Bound drugs can act as a reservoir
    • Hypoalbuminaemia may increase free drug
    • Use of combinations of plasma protein bound (PPB) drugs may displace each other, increasing amounts of free drugs
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10
Q

What is the volume of distribution (Vd)?

A
  • The volume of fluid required to contain the total amount of drug in the body at the same concentration as that present in the plasma
  • Is a theoretical volume
  • Vd= Dose given/C0
    • where C0 is the peak plasma drug concentration after equilibrium is achieved and before elimination has begun. This is generally derived from extrapolating the Plasma Drug Concentration (PDC)/time curve back to time 0.
    • With a known dose given i/v so that F=100%
  • Usually given in litres/Kg
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11
Q

At around what value does the volume of distribution (Vd) indicate about equal distribution to the extracellular fluid and intracellular fluid?

A

~0.6 L/kg

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12
Q

Describe the eliminiation of drug reactions.

A
  • Phase I
    • Makes the drug more reactive
    • Types of reactions
      • Hydrolysis
      • Reduction
      • Oxidation
        • Performed mainly by the hepatic microsomal enzymes, such as cytochrome p450
  • Phase II
    • Conjugates the drug for eliminiation
    • Types of reactions
      • Acetylation
      • Glucuronidation
        • Results in glucuronide conjugate which can be excreted in bile or become hydrolyzed in the gut
      • Conjugation to amino acids
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13
Q

Discuss the kinetics of drugs through the kidney.

A
  • Drug is filtered from the blood by Glomerular filtration
    • Passive process for which rate is dependent on blood flow, size of molecule and protein-binding
    • A drug bound to albumin cannot be filtered through the glomerulus
  • Drug is actively transported into the proximal convoluted tubule from surrounding capillaries
    • Active tubular secretion of weak acids and weak bases facilitates extraction from the blood, often against a significant concentration gradient.
  • Drug can be reabsorbed back into circulation from the distal convoluted tubule
    • Passive process
    • Lipid soluble molecules are reabsorbed from the tubular lumen
    • Dependent on degree of ionization of the drug (pKa) and pH of the urine
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14
Q

What is bioavailability and how is it calculated?

A
  • Defines the extent to which an administered dose of a drug enters the systemic circulation intact
  • Referred to as F
  • F = AUCcertain route of administration/ AUCiv
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15
Q

What is half life, what factors affect it, and how is it calculated?

A
  • Time taken for the plasma drug concentration to fall by 50%
  • Inversely proportional to the clearance and directly proportional to the volume of distribution
  • Affected by
    • Effects on access to sites of biotransformation or elimination
    • Interaction with other drugs
    • Physiological/pathological states
  • Calculated using
    • =0.693/K
      • Where K is the slope of the semi-log plasma drug concentration (PDC) versus time curve (first order kinetics)
    • =0.693* Vd/Clearance
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16
Q

Describe the clearance of a drug and how it is calculated.

A
  • Defined as the volume of blood cleared of all the drug by all elimination processes per unit time, measured in ml/min
  • Encompasses biotransformations as well as elimination
  • Clearance = Volume of distribution/K
    • Where K is the slope of the semi-log plasma drug concentration (PDC) versus time curve (first order kinetics)
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17
Q

What is the drug steady state and how can it be achieved?

A
  • Where the level of drug in the body remains stable from dose to dose
  • 95% SS is achieved after 5 half-lives and 99% SS is achieved after 7 half-lives
  • Can be achieved by
    • Intravenous continuous infusion
      • Preferred for use with drugs that have a short half-life
    • Loading dose of drug followed by a regular dose at fixed intervals
      • Preferred for use with drugs with a long half-life
    • Fixed intervals of a fixed dose of drug which takes about 5 half-lives to achieve
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18
Q

What is a drug’s EC50?

A

The concentration of drug required to produce 50% of the maximal response

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19
Q

What is a drug’s equilibrium disassociation constant?

A

Concentration of the drug required to occupy 50% of the receptors.

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20
Q

Describe the G-protein coupled receptor activation cycle.

A
  • Agonist interacts with the G protein coupled receptor brings about a conformational change which stimulates the alpha subunit
  • Alpha subunit coverts GDP to GTP
  • Alpha subunit dissociates with the beta and gamma subunits and is available to interact with the second messenger system in the cell
    • Adenylyl cyclase: alpha subunit interaction can result in either an increase or a decrease in adenylyl cyclase which results in an increase or decrease in cAMP
    • Phospholipase C: Interaction of the alpha subunit generally results in an increase in calcium in the cell via opening of calcium channels and/or release of calcium from intracellular stores
  • GTP can be converted back to GDP by GTPase (closely associated with alpha subunit)
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21
Q

What is tachyphylaxis?

A
  • Denotes the rapid loss of responsiveness to a drug following initial dosing
  • Receptor desensitization may be the reason for this
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22
Q

How can hepatic disease change the drug dosing regimen?

A
  • Effect of disease is complex and it may be difficult to change the dose/interval
  • Can causes changes in hepatic blood flow
  • Can cause changes in hepatic metabolism
  • Can cause descrease in albumin which causes changes in protein binding
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23
Q

List the legislative responsibilities for the Veterinary Medicines Directorate (VMD).

A
  • Assure safety, quality and efficacy of veterinary medicines
  • Ensure responsible, safe, and effective use of veterinary medicinal products
  • Protect public health, animal health, the environment, and promote animal welfare
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24
Q

What is the role of the Marketing Authorisation Veterinary Information Services (MAVIS)?

A
  • Designed to provide information on the work of the VMD, plans and results, as well as general developments on the control on veterinary medicines
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25
Q

What is the Suspected Adverse Reaction Surveillance Scheme (SARSS)?

A
  • National surveillance scheme which records and monitors adverse reactions
  • What is reported:
    • Adverse reactions (or lack of effect) in target animals and non-target individuals from exposure of licensed or unlicensed drugs
    • Level of drug residue in animal or tissues being higher than expected after withdrawal period
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26
Q

What is the legistlation surrouding Prescription-only medicine- Veterinary (POM-V)?

A
  • Can only be prescribed by a veterinarian following recent or often ‘clinical assessment’ of the animal or herd of animals by a vet
  • Can be dispensed by a Vet or Pharmacist
  • If the prescribing vet is also the supplier of the drug to the client, no written prescription is required
  • Can be advertised through price lists to VS, pharmacists and professional keepers of animals
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27
Q

What is the legistlation surrouding Prescription-only medicine- Veterinarian, Pharmacist, Suitably Qualified Person (POM-VPS)?

A
  • Can be prescribed by any registered qualified person (RQP)
  • Clinical assessment of the animal is not required and animal does not have to be seen
  • Sufficient information about the animal and the way it is kept must be known to the prescriber in order to prescribe and supply appropriately
  • Can be advertised through price lists to VS, pharmacists, SQP, professional keepers of animals, keepers of horses, and other veterinary care professionals
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28
Q

What is the legistlation surrouding Non-food animal- Veterinarian, Pharmacist, Suitable Qualified Person (NFA-VPS)?

A
  • For non-food animals (to avoid the issue with drug residue)
  • Do not have to be prescribed, but they can only be supplied by a veterinary surgeon, pharmacist or an SQP
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29
Q

What is the legistlation surrouding Authorized veterinary medicine- general sales list (AVM-GSL)?

A
  • No legal restrictions on the sale or supply by retailers
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30
Q

What is the legislation surrouding the cascade for non-food species in the United Kingdom?

A
  1. A product licensed for another condition in the same species or a product licenced for another animal species with the same condition
  2. A) A UK human licensed product or
    ​B) In accordance with an import certificate, a veterinary medicine authorized for veterinary use in another EU member state
  3. A product prepared extemporaneously by a veterinary surgeon, a pharmacist, or a person holding a manufacturer’s authorization as prescribed by the Veterinary Surgeon (VS); or a veterinary product licensed outwith the EU; or a human licensed product from outwith the UK
  • Additional requirements
    • Treatment for animals on a single holding
    • If the medicine is imported from another member state, it must be licensed for food animals in that state
    • Withdrawal period must be specified by prescriber
    • Active drug must be listed in Table of Allowed Substances in Comission Regulation EU No37/2010
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31
Q

What special considerations are there for the horse in temrs of the veterinary medicine cascade in the United Kingdom?

A
  • Horses are considered to be a food-producing species unless stated in the horse passport that the animal will not be used for human consumption
  • If the horse is for food, then only licensed drugs or drugs listed on the VMD “Substances essential for the treatment of horses” list may be used
  • Drugs used by have a specified withdrawal period or a 6-month withdrawal must be used
  • Drugs and vaccines should be listed on passport
  • If drug used is not licensed or on the ‘substances essential for treatment of horses’ list, the horse may never be used for human consumption and this should be indicated on the horse’s passport
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32
Q

List the schedules for controlled drugs. Describe the unique legistlation for each.

A
  • Schedule 1
    • Vets have no authority to possess or prescribe these
  • Schedule 2
    • Special requirements for requisition, prescribing, record keeping, storage and disposal
    • Requisition in writing to the supplier signed by the VS
    • Destroyed in the presence of a person authorised by the secretary of state for stocked drugs (not patient returns of drug)
    • Stored in a locked receptacle
  • Schedule 3
    • Special requirements for requisition, prescribing, record keeping, storage and disposal
    • Do not have to keep a record
    • Should be kept in a locked cabinet
  • Schedule 4
    • Requirement to keep invoices for 2 years and written prescription valid for 28 days
    • RCVS recommendation that ketamine use be tracked by informal register, kept in a locked cabinet and disposed of as for Schedule 2 drugs
    • Contains most of the benzodiazipines and the anabolic and androgenic steroids
  • Schedule 5
    • Invoices need to be kept for 2 years
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33
Q

For how long are written prescriptions valid? What are some other key characteristics of a good written prescription?

A
  • Only valid for 28 days (except Schedule 5)
  • Must have total quantity in words and figures
  • Must state strength and form of product
  • Directions must be specific
  • Must state “for animals under my care”
  • Should specify the prescriber’s RCVS number (under good practice)
  • Should only prescribe a 30-day supply under good practice
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34
Q

Describe the exemption scheme for small animal medicines.

A
  • Some veterinary products can be marketed for these species without a marketing authorization and therefore are not required to prove safety, quality or efficacy
  • The active ingredient, species it is used for, and how the product is to be used must be approved by the veterinary drug directorate
  • Only for pet animals not intended for human consumption
  • Products must be labelled clearly to show that they are being marketed under this scheme
  • Products containing antibiotics, narcotics, or phychotropic agents are not included in this scheme
  • Products intended for parenteral, ophthalmic, or aural administration may not be included in this scheme
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35
Q

What is the legislation surrounding medicated feedstuff (MFS)?

A
  • Can be classed as POM-V or POM-VPS
  • Prescriptions valid for 3 months but only 1 month’s worth can be manufactured at a time
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36
Q

What is the legislation surrounding supplying sheep dips?

A
  • Person supplied must have either a
    • Certificate of competence in the Safe Use of Sheep Dips (Certificate number must be kept for 3 year) sor
    • NPTC Level 2 Award in Safe Use of Sheep Dip
  • If active compound is organophosphorus, supplier must give purchaser two pairs of heavy duty gauntlet-style gloves and a laminated safety notice
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37
Q

How is noradrenaline eliminated from the nerve terminal?

A
  • Re-uptake type 1: taken up into the nerve terminal and broken down by monoamine oxidase
  • Re-uptake type 2: taken up by non-neuronal tissue (liver, for example) and broken down by catechol-o-methyl transfe
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38
Q

Describe the alpha1-adrenoreceptors.

A
  • Part of the sympathetic nervous system
  • Widely distributed throughout the body
  • Couple mainly to Gq (identification of the α subunit)
    • The second messenger system usually involves activation of phospholipase C leading to the formation of inosital triphosphate (IP3) and diacylglcerol (DAG). This ultimately causes increased calcium in target cell
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39
Q

Describe the alpha2-adrenoreceptors.

A
  • Part of the sympathetic nervous system
  • Some types are a presynaptic receptor, causing negative feedback on norepinephrine (NA) release, for example
  • Couple to G-protein receptors to inhibit adenylyl cyclase and thus decrease cAMP in the target cell.
    • For example, they are located postjunctionally in vascular smooth muscle (VSM) and cause vasocontriction upon stimulation because they decrease cAMP
  • Mediate sedation and have analgesic effect
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40
Q

Describe the Beta1-adrenoreceptors.

A
  • Part of the sympathetic nervous system
  • Couple to G-proteins which cause stimulation of adenylyl cyclase which increases cAMP. This, in turn, increases protein kinase A to allow more calcium to both enter and be released by the target cells.
  • Found mainly in the heart with stimulation causing
    • Increased force of contraction
    • Increased conduction
    • Increased rate of impulse formation
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41
Q

Describe the Beta2-adrenoreceptors.

A
  • Part of the sympathetic nervous system
  • Couple to G-proteins which stimulate or inhibit cAMP production
  • Main effects of stimulation:
    • Vascular smooth muscle relaxation
    • Bronchiodilation
    • Stabilize respiratory mast cells
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42
Q

Give an example of a neuropeptide which modulates the enteric nervous system.

A

Serotonin

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43
Q

Describe nicotinic receptors.

A
  • Found in the pre-ganglionic parasympathetic and sympathetic nervous systems (NN)
  • Found in the somatic nervous system (NM)
  • Ligand-gated ion channels which increase permeability to sodium and potassium upon stimulation with acetylcholine
    • Depolarizes the target cell and transmits nerve impulses
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44
Q

Describe muscarinic receptors.

A
  • Found post-ganglionic parasympathetic nervous system
  • G-protein coupled receptors which are stimulated with acetylcholine
  • 5 subtypes exist
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45
Q

What is chronotropy?

A

Change in heart rate

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46
Q

What is Carbachol and how is it used?

A
  • Muscarinic agonist choline ester
  • Used to induce gastric motility and topically to induce miosis
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47
Q

What is Pilocarpine and how is it used?

A
  • Muscarinic agonist cholinomimetic alkaloid
  • Used as a topical solution applied to the eye to induce myosis
    • Used for the treatment of glaucoma (condition with increase of intraoccular pressure). Constricting of the pupil helps to open up the drainage angle
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48
Q

What is Neostigmine and what is it used for?

A
  • Acetylcholinesterase inhibitor
  • Used for the reversal of non-depolarizing muscle relaxants
  • Used for treatment of myastheia gravis
    • In the most common cases, muscle weakness is caused by circulating antibodies that block acetylcholine receptors at the postsynaptic neuromuscular junction, inhibiting the excitatory effects of the neurotransmitter acetylcholine on nicotinic receptors at neuromuscular junctions (nicotinic subtype m receptors). Neostigmine allows for a higher concentration of endogenous acetylcholine to be present at the neuromuscular junction by limiting the breakdown of endogenous Ach through inhibition of acetylcholine esterase. Thus, there is a greater amount of endogenous Ach present at the neuromuscular junction to overcome the blocked cholinergic receptors.
  • Can be given orally or intravenously
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49
Q

What is Atropine and what is it used for?

A
  • Muscarinic antagonist (parasympatholytic)
  • Can be given i/m, i/v, and p/o
  • Metabolized in the liver and excreted by the kidneys
  • Uses
    • Premedicant to decrease salivation
    • Antispasmotic agent of the gut
    • Decreases gastric secretion
    • Dilation of the pupil for examination
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50
Q

What is cycloplegia?

A

Paralysis of the ciliary muscle of the eye, resulting in a loss of accommodation

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51
Q

How are parasympathetic drugs used peri-operatively?

A
  • Non-depolarizing muscle blocker is administered as a relaxant
    • Acts by competitively blocking the binding of ACh to its receptors at the neuro-muscular junction
  • Subsequent reverse of the muscle blocker is achieved by administering acetylcholine esterase inhibitor to increase acetylcholine at the nicotinic/muscarninic receptors and regain nervous function
  • Muscarinic antagonist is also administered to control unwanted muscarinic effect (excessive parasympathetic function)
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52
Q

What is adrenaline? Describe its actions in the body.

A
  • Non-selective sympathetic agonists (acts at both α- and β-adrenoreceptors)
  • Increases heart rate and force of contraction
  • Induces vasoconstriction
  • Can induce tachycardias and arrhythmias
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53
Q

What is isoprenaline and what is its action in the body?

A
  • Sympathetic nervous drug
  • Non-selective β-adrenergic agonist
  • Has positive inotropic (increased contractility of the heart) and chronotropic effects (changes the heart rate)
  • Can induce arrhythmias and, in severe cases, myocardial necrosis
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54
Q

What is dopamine and what is its action on the body?

A
  • Sympathetic non-selective agonist
  • Stimulation by low doses of dopamine leads to increase in intracellular cAMP
  • In blood vessels, it inhibits norepinephrine release and acts as a vasodilator (at normal concentrations)
  • Leads to increased renal perfusion and filtration in the kidneys, increasing sodium excretion and urine output
    • Used for prevention and management of acute renal failure
  • Dopamine at high doses can induce vasoconstriction through vascular α1-adrenoreceptors
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55
Q

What is phenylpropanolamine and what are its effects on the body?

A
  • Sympathetic α-agonist drug
  • Has tyramine-like activity in that it induces the release of NA from the nerve terminal
    • Most important use is in the treatment of urinary incontinence in the bitch
    • Has been used as a nasal decongestant
    • Can induce hyperexcitability, especially in cats
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56
Q

What is dobutamine and what are its actions on the body?

A
  • Sympathetic beta1-agonist drug
  • Will have primarily cardiac effects; increasing heart rate and force of contraction of the heart
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57
Q

What is clenbuterol and what are its actions in the body? What are some other drugs with similar action?

A
  • Sympathetic Beta2-agonist drug
    • Includes Terbutaline and isoxuprine
  • Induces bronchodilation
    • Can be used in the treatment of Reccurent Airway Obstruction (RAO) in horses
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58
Q

What is phenyleprine and what are its actions on the body? Name a drug with similar actions.

A
  • Sympathetic a1-adrenoreceptor agonists drug
    • Includes Prazosin
  • Will induce vasoconstriction, increase the force of myocardial contraction, and induce mydriasis
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59
Q

What is clonidine? Describe its effects in the body.

A
  • Sympathetic a2-Adrenoceptor agonists drug
  • Has central sedative effects
  • Stimulates the release of Growth hormone-releasing hormone (GHRF)
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60
Q

What is phenoxybenzamine? Describe its actions in the body.

A
  • Sympathetic alpha1-agonist drug
  • Cause vasodilation
  • Treats urinary retention
61
Q

What is Timolol and what is it used for?

A
  • Beta-adrenoreceptor antagonists
  • Used for glaucoma treatment
62
Q

What is asprin? Describe its effects in the body.

A
  • Non-steroidal anti-inflammatory drug
  • Irreversibly binds and inactivates cyclo-oxygenase (by acetylation) and prevents the formation of inflammatory products
  • Antithrombotic effect
    • Low-dose aspirin use irreversibly blocks the formation of thromboxane A2 in platelets, producing an inhibitory effect on platelet aggregation during the lifetime of the affected platelet
    • At high dose, synthesis of prostacyclin (PGI2; inhibits platelet activation) by endothelial cells is inhibited
63
Q

What is paracetamol and describe its metabolism. In which species should this drug not be used?

A
  • Non-steroidal anti-inflammatory
  • Metabolism can occur by either:
    • Glucuronidation
      • Cannot be performed by cats, so cats rely on other pathways for metabolism
    • Sulphate conjugation
    • N-hydroxylation
      • Yields N-acetyl-benzo-quinoneimine (NABQI)
        • Binds to glutathione, but if glutathione is saturaiton it binds to hepatic proteins causing necrosis
        • Produced in excess in cats (because cats are not able to use glucuronidation pathway) to cause hepatic necrosis
          • Paracetamol should not be used in cats
64
Q

What is phenylbutazone? What is unique about the legal requirments of its use?

A
  • Non-streroidal anti-inflammatory
  • Phenylbutazone cannot be administered to food-producing animals because it can cause aplastic anaemia in humans
65
Q

What is Carprofen? What is it used for?

A
  • Non-steroidal anti-inflammatory
  • Poor cyclo-oxygenase inhibitor and potent anti-inflammatory
  • Can be used as a perioperative analgesic with reduced risk of nephropathy
66
Q

What is robenacoxib? What is one of the important reasons it was developed?

A
  • Non-steroidal anti-inflammatory (NSAID)
  • Developed to prevent gastrointestinal upset normally associated with NSAIDs
67
Q

What is polysulphated gycosaminoglycan? Why is it used?

A
  • Anti-inflammatory drug (semisyntheticglycosaminoglycan prepared from bovine tracheal cartilage and composed of a polymeric chain of repeating disaccharide units.)
  • Stimulates matrix production by chondrocytes
68
Q

What is hyaluronic acid?

A
  • Anti-inflammatory non-sulphated proteoglycan
  • Imparts important structural characteristics to synovial fluid and cartilage administeresd as a condroprotective agent in dogs and horses
69
Q

What are the adverse effects of exogenously adminstered steroids? How can these effects be mitigated?

A
  • Possible adverse effects of administered steroids:
    • Gastric ulceration
    • Muscle atrophy
    • Cutaneous atrophy
    • Hyperglycaemia
    • Osteoportotic effect
    • Decrease absorption and increased excretion of calcium
    • Increase PTH activity
    • Decrease activity of osteoblasts and increase activity of osteoclasts
    • Degeneration of epiphyseal cartilage in young animals
    • Mineralocorticoid activity resulting in sodium and water retention and loss of potassium
  • Adverse effects can be avoidance methods:
  • Alternate day therapy
  • Use of short-acting formula
  • Administration of steroid at a time of peak endogenous levels (in the morning for dogs or in the evening for cats)​
70
Q

Name the short acting steroids. For how long do their effects persist?

A
  • Short acting steroids with <24 hours activity:
    • Prednisolone
    • Prednisone
    • Methylprednisolone
71
Q

Name the long-acting steroids. For how long do their effects persist?

A
  • Short acting steroids with >24-hour activity:
    • Dexamethasone
    • Betamethasone
    • Trimacinolone
72
Q

What is Addison’s Disease? How can it be treated?

A
  • Addison’s Disease
    • Deficiency of production of steroids from the adrenal cortex
    • Most common in young female dogs (idiopathic)- animals generally present collapsed, bradycardic, hyperkalaemic, hyponatraemic and dehydrated
    • Treated acutely with hydrocortisone
    • Long term managed with fludrocortisone (high glucocorticoid and mineralcorticoid activity) administered orally on a daily basis)
73
Q

What is Cushing’s disease?

A
  • Cushing’s disease is the overproduction of glucocorticoids due to a pituitary adenoma (ACTH increased) or due to an adrenal tumour
  • Can result from prolonged treatment with glucocorticoids (Iatrogenic Cushing’s disease)
  • Signs: polydipsia, polyuria, polyphagia, elevated liver enzymes, pot-bellied appearance (because of redistribution of fat and muscle tissue)
74
Q

What are the benzimidazoles? Describe their spectrum of action, absorption/distribution, mechanism of action, and metabolism.

A
  • Broad spectrum (adult and larval stage) anthelmintics for most domestic species (except lactating animals)
  • Administered orally
  • Poorly absorbed from the gastrointestinal tract (except for albendazole and oxfendazole)
  • Metabolism is variable
    • In general, most of the drug is excreted unchanged in the faeces and the urine (some in the urine)
  • Mechanisms of action
    • Bind to nematode tubulin and prevent the formation of microtubules
75
Q

Name some examples of the Benzimidazoles and give a key feature of each.

A
  • Triclabendazole
    • effective against mature and immature fluke (trematode) but not nematodes
  • Albendazole
    • has some efficacy against adult stages of nematodes
  • Pro-benzimidazoles (Febantel, netobimin and thiophanate
    • More water soluble than other benzimidazoles
    • Require conversion to active form in the liver
76
Q

What are the Macrocyclic Lactones? Describe their mechanism of action and toxicity in the host.

A
  • Anhelmintics which comprise the avermectins and milbemycins (endectocides)
  • Potentiate the effect of glutamate at chloride channels in the parasite which leads to paralysis of the parasite
  • Toxicity is related to the binding of the anthelmintic to the GABA related neurons in the host
    • In general, these agents do not cross the Blood-Brain Barrier but there are some individual breed sensitivities (Collies and Australian Shepherds and Murray Grey Cattle can have ivermectin sensitivity due to P-glycoprotein mutation)
77
Q

What are the avermectins? Give some examples and describe their key characteristics.

A
  • Macrocyclic lactone anhelminths
  • Examples
    • Eprinomectin
      • The drug is partitioned away from the milk so no withdrawal periods are required when used in lactating cattle
    • Selectamin
      • Used in cats and dogs
      • Large amounts are partitioned into the sebaceous glands, providing a reservoir
      • Safe to use in Collies
      • Use
        • Effective against lung worm
        • Heart worm prophylaxis
        • Effective against gastrointestinal nematode
        • Sarcoptic mange mite
        • Fleas
78
Q

What are the Milbemycins. Give an example and key characteristics.

A
  • Macrocyclic lactone anthelmintic
  • Moxidectin
    • Can be used in all domestic species
    • Very highly lipophilic and persists in the tissue for over a month
    • Excreted in the feces
  • Milbemycin oxime
    • Used in cats and dogs for heart worm control once a month. Also targets round worm, hook worm, and whip worm
79
Q

What are the endectocides? What parasitic species do they target?

A
  • Avermectins, milbemycins (macrocylic lactones)
  • Have an effect on nematodes and ectoparasites (no effect on fluke or tapeworms as the receptors sites on which they act are absent in these)
80
Q

What are the Imidazothiazoles? Describe their spectrum of action, mechanism of action, and toxicity.

A
  • Anthelminitic
  • Spectrum of activity
    • Adults and larvae of Gastro-intestinal nematodes and lung worm
    • Licenced for use in sheep and cattle
  • Mechanism of action
    • Target nervous system of parasite
      • Act at acetylcholine/nicotinic receptors in the ganglia of the parasite which causes parasite to lose hold on the animal
  • Some toxicity due to activity at nicotinic receptors and some suggestion of muscarinic stimulation of the host (parasympathetic nervous system)
81
Q

What is Levamisole? What is a key characteristic of this drug?

A
  • Imidazothialzole anthelmintic
  • Has immunostimulant effect: restores numbers of T lymphocytes
82
Q

What is Monepantel (Zolvix)? Give some key characteristics of this drug.

A
  • Ono acetonitrile derivative anthelminitic drug
  • Targets the nicotinic acetylcholine receptor of the parasite as an agonist
  • Used to target GI nematodes in sheep which are multi-drug resistant
  • Requires 7-day meat withdrawal (Relatively short withdrawal period)
  • Targets L4 and adult stage nematodes
83
Q

What is Derquatel? Give some of its key characteristics.

A
  • Spiroindole derivative anthelmintinc drug
  • Spectrum of activity is adult/immature GI nematodes and adult lung worm
  • Antagonist at the nicotinic acetylcholine receptor
  • Always used in combinations
  • Used in sheep for parasites that are multi-drug resistant
84
Q

What is Pyrantel? Describe its key characteristics.

A
  • Imidazothiazole dervative anthelmintic
  • Can be administered as a pamoate salt (with reduced gastrointestinal absorption) or tartrate salt (rapidly absorbed into the systemic circulation)
  • Parent drug and metabolites excreted in the faeces (except in the dog where urinary excretion is more important)
  • Has immuno-stimulant effects
  • Spectrum is mainly gastrointestinal round worm in horse, dogs, and cats
85
Q

What is Emodepside? Describe its key characteristics.

A
  • Cyclo-depsipeptide anthelminitic
  • Spectrum of activity
    • Broad spectrum in the cat
    • Targets: toxacara cati, toxascaris leonina, anclystoma tubaeforme immature/larval stages
  • Administered topically
86
Q

Give examples of flukicides.

A
  • Salicyclanide
  • Nitroxynil
  • Clorsulon
87
Q

What is Pranziquantel? Describe its key characteristics.

A
  • Cestocide (efficacy primarily against cestodes (tapeworms))
  • Causes calcium influx into the parasite, inducing tetanic contraction
88
Q

What is Piperazine? Describe its key characteristics.

A
  • Anhelminthic drug
  • Causes hyperpolarization at the neuromuscular junction, inducing flaccid paralysis in parasites
  • Used to treat roundworm even in young animals (puppies and kittens)
  • Used in pigeons
89
Q

What is Melarsomine hydrochloride? Describe its key characteristics.

A
  • Arsenical anthelminthic drug
  • Mechanism of action: Trivalent arsenic binds to sulfhydryl groups on proteins, altering their function. Mitochondrial enzymes are especially susceptible to damage energy-producing function
  • Only used if there are no other safer options available
  • Effective to treat animals with the adult form of heartworm
  • Narrow therapeutic range
90
Q

What are some methods to prevent anthelmintic resistance?

A
  • Rotational used of antelmintics
  • Use of correct dose and regimen
  • Use in combinations
  • Use of animal management to reduce need
91
Q

What is the mechanism of action of the pyrethrins and pyrethroids? Which animals are sensitive to these compounds?

A
  • The pyrethrins and pyrethroids are liposoluble and penetrate the ectoparasite cuticle by passive diffusion. The drug is passed though insect body via insect haemolymph and acts on nerve membrane by modifying gating kinetics of sodium channels to cause neuroexcitation and then paralysis
  • Aquatics, ferrets, and cats are very sensitive to these compounds
92
Q

Describe the insect metabolism of pyrethrins and pyrethroids. How can a drug be formulated to take advantage of this quality?

A
  • Drug is metabolised by insect mixed-function oxidases (MFO) and esterases
    • MFO inhibitors synergise the activity of pyrethroids
  • Metabolic hydrolysis is more rapid for the trans isomers than cis isomers
    • Different strengths of product depending on the cis content (some products may be labelled as “high cis” and are not metabolized as readily by insects as a regular formula)
93
Q

Describe resitance mechanisms of insects to the pyrethroids and pyrethrins.

A
  • Behavioural
    • insect avoids contact
  • Penetration resistance
    • modified exoskeleton to prevent drug entry
  • Insect receptor site insensitivity
  • Metabolic resistance
    • Insect increases its ability to metabolize the drug
94
Q

What is Piperonyl butoxide?

A
  • Ectoparasiticide used alone or to synergize pyrethroids
  • Inhibits insect microsomal enzymes and increases efficacy of the pyrethroid
95
Q

What is Diazinon? What is its mechanism of action?

A
  • Organophosphate ectoparasiticide which forms a complex with the acetylcholinesterase enzyme
96
Q

What is Amitraz? Describe its use, mechanism of action, and contraindications.

A
  • Triazepentadiene ectoparasiticide
  • Mechanism of actions
    • Monoamine oxidase inhibitor and Alpha2 receptor agonist
      • Causes Increased nerve activity in the parasite
  • Uses
    • Demodetic mange, sarcoptic mange, fleas and ticks in dogs
    • Spot-on preparation in combination with Fipronil
  • Contraindicated in cats, horses, and Chihuahuas
97
Q

What is Cyromazine? Describe its key characteristics.

A
  • Ectoparasiticide
  • Disrupts insect growth regulation
  • Used as a prophylaxis against blowfly, ticks, and lice
  • Used to treat lice
  • 3-day meat withdraw period required after use
98
Q

What is fipronil? Describe its key characteristics.

A
  • Phenylpyrazole ectoparasiticide
  • Blocks GABA and Glutamate-gated chloride channels to kill adult parasites before egg-laying
  • Accumulates in the skin after topical application
  • Used in dogs and cats for fleas and ticks
  • Safe to use in puppies and kittens
99
Q

What is Pyriprole? Describe its key characeteristics.

A
  • Phenylpyrazole ectoparasiticide
  • Spot-on solution licenced only in dogs
  • Used for the treatment and prevention of fleas and ticks
  • Acts as an antagonist at GABA-gated chloride channels causing uncontrolled nerve activity lead to death of the parasite
  • Distributed through the skin and hair with systemic exposure (toxicity-associated with metabolites in overdosing)
100
Q

What is Afoxolaner? Describe its key characteristics.

A
  • Isoxazonlines ectoparasiticide
  • GABA antagonist with activity against fleas and ticks in dogs
  • Administered as a chewable tablet with good oral bioavailability
101
Q

What is Fluralaner? Describe its key characteristics.

A
  • Isoxazonlines ectoparasiticide
  • GABA antagonist with activity against fleas and ticks in dogs
  • Administered as a chewable tablet with good oral bioavailability
102
Q

What is Imidacloprid? Describe its key characteristics.

A
  • Choronicotinyl nitroguanide ectoparasiticide
  • Binds to CNS nicotinic receptors in insect to cause paralysis and death
  • Available as spot-on preparation for flea control in the dog and the cat
103
Q

What is Nitenpyram? Describe its key characteristics.

A
  • Neonicotinoid ectoparasiticide
  • Binds to acetylcholine niotinic receptors of the parasite
  • Treats fleas in dogs and cats
  • Given orally with high oral bioavailability
  • Good for treating heavily infected animals
104
Q

What is Spinosad? Describe its key characteristics.

A
  • Combination of tetracyclic macrolides ectoparasiticide
  • Targets the nicotinic acetylcholine receptors in the parasite
  • Administered orally with food
  • For use in dogs only
105
Q

What is Indoxacarb? Describe its key characteristics.

A
  • Ectoparasiticide
  • Pro-drug adminsted as a spot which is ingested by flea to metabolizes it to the active form
  • Active form of drug Inhibits voltage-operated sodium channels
106
Q

What is Lufenuron? Describe its key characteristics.

A
  • Benzoyl urea derivative insect growth regulator
  • Drug is administered to host and it accumulates in fat. It is then ingested from the blood by parasitic fleas. The drug interferes with chitin formation in the larvae and prevents the production of viable eggs
  • Administered as a combination with milbemycin oxime for broader parasite cover
107
Q

Give some examples of compounds used for environmental flea control.

A
  • Methoprene (insect growth regulator/juvenile hormone agonist)
  • Pyriproxifen
  • Permeterins (pyrethroid) and amitraz
108
Q

Give some examples of fly repellants.

A
  • Citronella oil
  • Diethyltoluamide
  • Dimethylphthalate
109
Q

Give some examples of anti-otodectes cyanotic agents.

A
  • Thiabendazole
  • Permetrhin
  • Monosulfiram
  • Canaural commercial drug combination
110
Q

What are Ionophones? Describe the target spectrum, mechanism of action and give some examples.

A
  • Broad spectrum anticoccidial agents in poultry and cattle
  • Mechanism of action: interefere with ion transport across cell membrane
  • Examples
    • Monensin
    • Salinomycin
    • Lasalocid
    • Narasin
    • Maduramicin
111
Q

What are the Sulphonamides? Describe their target spectrum, their mechanism of action

A
  • Coccidiostatic drug for treatment of cattle, sheep, and pigeons
  • Mechanism of action: interferes with folic acid synthesis in the protozoa by competing with para-amino benzoid acid (PABA) for dihydropteroate synthetase enzyme (affinity is similar)
112
Q

What are the Diaminopyrimidines? Describe their target spectrum, their mechanism of action

A
  • Anti-Coccidial drug for treatment of dogs, cats, rabbits, poultry, and ruminants
  • Mechanism of action: Inhibits dihydrofolate reductase which is required by the protozoa to produce purine and pyrimidine nucleotides
113
Q

What is amprolium?

A
  • Anti-coccidial drug used for prophylaxis in chickens and turkeys
114
Q

What is Imidocarb? Describe its key characteristics.

A
  • Anti-coccidial drug
  • Used to treat babesiosis in cattle and dogs
  • May be used to treat ehrlichiosis in dogs
115
Q

What is Allopurinol? Describe its key characteristics.

A
  • Anti-coccidial drug
  • Interferes with RNA in the leishmaniasis parasite
116
Q

What is Griseofulvin? Describe its target spectrum, mechanism of activity, pharmacokinetics, and contraindications.

A
  • Fungistatic antibiotic
  • Mechanism of action
    • Taken up into fungal cell and disrupts the mitotic spindle
  • Target spectrum
    • Dermatophytosis (ringworm), Microsporum, tricophytan, epidermophytan
  • Pharmacokinetics
    • Fatty meal enhances oral bioavailability
    • Distributes preferentially to the stratum corneum, hair, and nails
    • Has a short plasma half-life but binds tightly to skin cells and stays there until those cells are shed
    • Metabolized in the liver to demethylgriseofulvin before being gluconuridated (cannot be performed by cats)
  • Contraindicated in cats
117
Q

What is Flucytosine? Descrbe its mechanism of action and spectrum of activity.

A
  • Anti-fungal
  • Mechanism of action
    • Fungicidal: taken up into the fungal cell and converted to 5-fluorouracil by cytosine deaminase. This compound is then incorporated into mRNA and causes faulty protein synthesis.
  • Spectrum of activity
    • Narrow
  • Use confined to treatment of C.neoformans and Candida as resistance is rapidly developing
118
Q

What is Amphotericin B? Describe its spectrum of activity, mechanism of action, pharmacokineticsm, and toxicity in the host.

A
  • Polyene anti-fungal drug
  • Mechanism of action
    • Fungicidal by binding to ergosterol in the fungal cell membranes causing disruption
  • Spectrum of activity is broad
  • Pharmacokinetics
    • Poor oral bioavaialbility
    • Highly plasma protein bound
  • Toxicity
    • Highly nephrotoxic due to binding of amphotericin to cholesterol in renal tubules
119
Q

What is Nystatin? Describe its key characteristics

A
  • Polyene anti-fungal drug
  • Mechanism of action
    • Fungicidal by binding to ergosterol in the fungal cell membranes causing disruption
  • Used topically
  • Shows no absorption from the gastrointestinal tract
120
Q

What is Natamycin? Describe its key characteristics

A
  • Polyene anti-fungal drug
  • Mechanism of action
    • Fungicidal by binding to ergosterol in the fungal cell membranes causing disruption
  • Broad-spectrum of action
  • Used topically
  • Shows no absorption from the gastrointestinal tract
121
Q

Describe the mechanism of action of the azole antifungals agents.

A
  • Inhibit the formation of ergosterol necessary in the structure of the fungal cell membrane (cytochrome P450 dependent)
122
Q

Name the topical azole antifungals.

A

Clotimazole, miconazole, enilconazole

123
Q

Name the systemic azole antifungals.

A

Ketoconazole, fluconazole, and itraconazole

124
Q

What is Terbinafine? Describe its mechanism of action, pharmacokinetics, and distribution.

A
  • Anti-fungal allylamines
  • Mechanism of action: Inhibits squalene epoxidase and reduces ergosterol production. Squalene accumulate in the cell membrane (because it is not being metabolized to anything), leading to cell death
  • Given orally for dematophyte infections
  • Lipophylic and penetrates keratinized tissues where it persists
  • Has been used in the dog and cat although not licensed
125
Q

What are the echinocandins? Describe its key characterisitics.

A
  • Antifungal drugs
  • Target and inhibit an enzyme called glucan synthase which then prevents polysaccharide production to target the cell wall
126
Q

What is Acyclovir? Describe its mechanism of action.

A
  • Anti-viral drug
  • Acts by inhibiting viral DNA polymerase
127
Q

What is zidovudine? Describe its mechanism of action and indication for use.

A
  • Anti-viral drug
  • Phosphorylated by cellular enzymes to active form where it inhibits RNA dependent DNA polymerase and causes chain termination
  • May be usedful in FIV at the symptomatic stage
128
Q

What are omega interferons? Describe their use.

A
  • Antiviral drug
  • Used to treat canine parvovirus
129
Q

What is the Minimal inhibitory concentration (MIC)?

A

Highest dilution (specific concentration) of a drug at which there is no growth after incubation of a microbe.

130
Q

What is the mechanism of action of the beta-lactams?

A
  • Inhibit trans-peptidase enzymes (penicillin-binding proteins) and disrupts cross-linking of glycopeptide polymer in bacterial cell wall to prevent bacterial cell wall formation
  • Lyses cell wall in growing cells (particularly rapidly-growing cells)
  • Bactericidal
131
Q

What is the mechanism of action of the fluoroquinolones?

A
  • Inhibit bacterial DNA gyrase (topoisomerase II) resulting in bacterial cell death
132
Q

Describe the mechanism of action of the aminoglycosides.

A
  • Penetrate bacterial cell membrane
    • Oxygen-dependent active transport by a polyamine carrier
  • Bind to ribosome and alter codon-anticodon recognition
  • Cause defective bacterial proteins to be produced
    • The incorrect tRNA links up with the coding region on the mRNA causing the wrong amino acids to be added to the extending peptide chain
133
Q

Describe the mechanism of action of the macrolides.

A
  • Inhibit protein synthesis in the bacterial organism
    • Bind to 50S subunit of the ribosome to ultimately inhibit translocation (movement of tRNA from A site to the P site) which results in the production of truncated peptides
134
Q

Describe the mechanism of action of the lincosamides.

A
  • Inhibit bacterial protein synthesis by binding to the 50S ribosomal unit of the bacterial ribosome and inhibit peptidyl transferase (important for the movement of the extending peptide chain from its transfer RNA on the P site to join the new amino acid that has been added to the tRNA on the A site)
135
Q

Describe the mechanism of action of the tetracyclines.

A
  • Inhibit bacterial protein synthesis:
    • Enter bacteria by passive diffusion (outer cell wall) and active carrier-mediated transport (inner cell membrane)
    • Bind to the 30S subunit of the bacterial ribosome
    • Prevent access of aminoacyl tRNA onto the A site of the ribosomal/mRNA complex
    • Prevent elongation of peptide chain
  • Bacteriostatic
136
Q

Describe the mechanism of action of chloramphenicol.

A
  • Binds irreversibly to the 50S subunit of the bacterial ribosome and blocks the action of peptidyl transferase, resulting in truncated proteins
137
Q

Describe the mechanism of action for sulfonamides.

A
  • Competitive inhibitors of para-aminobenzoic acid acid (PABA) for dihydropteroate synthestase enzyme required for the formation of purine and pyrimidine nucleotides
  • Bacteriostatis
138
Q

Describe the mechanism of action of the diaminopyrimidines.

A

Inhibit dihydrofolate reductase (DHFR) in the pathway of folic acid precursor to purine and pyrimidine nucleotides

139
Q

What is Metronidazole? Describe its spectrum of activity and its mechanism of action.

A
  • Nitromidazole antimicrobial
  • Narrow spectrum of activity: anaerobic organisms only (action only occurs under anaerobic conditions), some protozoa
  • Mechanism of action
    • Inhibit nucleic acid function under anaerobic conditions
    • Reduction of nitro-group yields unstable intermediates causing loss of helical structure of DNA causes strand breakage causing cell death
140
Q

What is Rifampin? Describe its spectrum of acticty and mechanism of action.

A
  • Bactericidal drug
  • Mechanism of action: inhibits RNA polymerase (enzyme which catalyses the transcription of DNA to RNA)
  • Spectrum of activity
    • Gram positive, anerobes, chlamydophila, rickettsia
    • Antifungal and antiviral activity
    • Rhodococcus equi
    • Atypical mycobacterial lesions in cats
141
Q

What are polymyins? Describe their mechanism of action and spectrum of activity.

A
  • Topical bactericidal preparation
  • Mechanism of action
    • Surface active agents which dirupt the cell membrane phospholipids
    • Bind to LPS which may prevent endotoxaemia and inhibits the production of cytokines by LPS induced by macrophages
  • Spectrum of action: gram negative organisms (except for Proteus)
142
Q

What is Novobiocin? Describe its key characteristics.

A
  • Topical anti-microbial
  • Mechanism of action: Inhibits nucleic acid synthesis
  • Anti-microbial activity: Gram positive
  • Used in intramammary preparations
143
Q

What is fusidic acid? Describe its key characteristics.

A
  • Lipophilic topical steroid antibiotic
  • Mechanism of action
    • Inhibits bacterial protein synthesis by binding aminoacyl tRNA to ribosomal A site
  • Active against gram positive bacteria
  • Used for occular, skin, and ear infections
144
Q

What is Framycetin? Describe its key characteristics.

A
  • Bacteriocidal Aminoglycoside
  • Present in aural preparations targeting gram negative organisms
145
Q

What is mupirocin? Describe its key charateristics.

A
  • Primarily used for staphylococcal infections
  • Inhibits protein synthesis through inhibition of tRNA synthetase
  • Has some antifungal activity
  • Routine use is actively discouraged as it is used in human medicine against MRSA
146
Q

What is Gonadotropin-releasing hormone (GnRH) drug and what is its clinical use?

A
  • Synthetic analogs contain amino acid substitutions which increase bio-potency by increasing resistance to proteolytic degradation and increasing affinity for GnRH receptors
  • Clinical uses
    • Induction of follicular growth and ovulation
    • Treatment of post-partum anoestrus in cows
    • Induction of ovulation
    • Timing of ovulation in mares (and cattle)
      • Follicular cysts in cattle
      • Synchronization of oestrus in cattle
    • Use post-service to possibly improve pregnancy rates
147
Q

How does GnRH function in the body?

A
  • Pulsatile secretion from the pituitary gland
  • Sensory stimuli can trigger an increase in GnRH pulsatility leading to LH surge and ovulation. At low pulsatility, causes FSH release
148
Q

How is chorionic gonadotrophin drug used clinically?

A
  • Induction of ovulation and superovulation - hCG
    • Timing of ovulation in mares and cows
    • Follicular cysts in cows
  • Induction of follicular growth during anoestrus- eCG/rFSH
    • In combination with progesterone implants to advance breeding season in sheep and goats
    • In combination with progesterone implants in anoestrus cows
    • In combination with human chorionic gonadotrophin to advance puberty in gilts
  • HCG stimulation test for detection of cyptorchidism in horses
    • Increase in testosterone levels in blood in response to an injection of hGC
  • Induction of spermatogenesis or to enhance libido in any species (eCg/rFSH)
149
Q

Describe the clinical use of oxytocin.

A
  • Dystocia due to uterine inertia
  • To promote uterine involution
  • Expulsion of retained fetal membranes (equine not bovine)
  • Uterine prolapse
    • Oxytocin reduces the size of the uterus by increases uterine tone
  • Facilitates the clearance of uterine discharge in mares
  • Induction of parturition in mares
  • Promotes milk let down (but does not promote lactogenesis)

Clinical Foundations Course (6 decks)

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