Pharmacology Flashcards
What is Nexium commonly used to treat?
Acid Reflux or GORD
What is Cartia and what is it used for?
Low dosage Aspirin used to prevent blood clots for patients with high CVD risks
Usage of asthma inhalers without a spacer can result in what?
Oral Candidiasis from diffused corticosteroids
Isotretinoin (Accutane) is a commonly used drug to treat severe acne. What are the oral side effects?
Dryness of oral mucosa and xerostomia
What is the main dental issue that can occur from Bisphosphonate usage?
Bisphosphonate related osteonecrosis of the jaw (BRONJ)
What is Bisphosphonates commonly used for?
Treatment of Osteoporosis
Cancer treatment of multiple myeloma
A patient presents that is taking Oral Bisphosphonates. Is dental treatment contraindicated?
No
What preventions must be taken when treating a patient taking IV Bisphosphonates?
Pre/Post Operative AB Cover: Clindamycin
and Chlorhexadine mouthwash to reduce bacterial load
FOSAMAX (Alendronate sodium) what sort of drug?
Bisphosphonate
How does propanolol work to combat hypertension?
It is a non-selective beta-adrenergic blocker.
lt blocks beta-adrenergic receptor sites and therefore causes smooth and
skeletal muscle arteriole dilation (literally bIocks effect of adrenaline oh beta-adrenergic receptors which are part of the fight or flight response. lf these sites are blocked there is no contraction of smooth or skeletal muscle) It is a|so likely to have direct effects on the myocardium. For these reasons it is used to treat hypertension and abnormally fast heart rate.
Why is combining alcohol with sertraline (a SSRI antidepressant) a bad idea?
Alcohol = decreased serotonin production SSRI = decreased serotonin resorption
Overall effect, decreased neurotransmitter activity: slower reaction time, poorer motor skills, depressed heart rate/blood pressure
What is sertraline (a SSRI antidepressant) commonly known as?
Zoloft
What are 4 principles of rational drug prescribing?
Right drug
Right dose
Right frequency
Right duration: Acute vs Chronic
What informational sources should dentists use for pharmacological information?
Australian Medical Handbook (AMH) 2016 best practice
Therapeutic Guidelines 2012 (v2): Oral and Dental
MIMS is unreliable and not practical
What are the major classes of prescriptions that dentists can prescribe on PBS?
Anti-infectives (Antibiotics) Antispasmodics, propulsives: gastric issues Antiemetics Local anaesthetics Adrenergic/dopaminergics Corticosteroids: soft tissue Anti-inflammatory Opioids Antiepileptics Anticholinergics Anxiolytics/sedatives
What does drug therapy hope to achieve?
- Prevent disease: influenza, measles/mumps
- Cure disease: pneumonia, some cancers
- Decrease mortality/prolong life: Heart attack / stroke
- Decrease sickness: Asthma, epilepsy
- Decrease symptoms of illness: Headache, cough/cold, pain
What are examples of non xenobiotic drugs that can be administered in the body?
Thyroxin, Insulin, Adrenaline
What is a xenobiotic?
Chemical substance not synthesised in the body and must be introduced into the body from outside
What is the smallest molecular weight drug?
Lithium - MW 7 (used for mania/bipolar)
What is Tissue plasminogen activator used for?
Emergency dissolving of blood clots for heart attacks
What is the lock and key concept?
A drug that has a good fit, high affinity, high specificity to a binding site
How does Allopurinol work?
Allopurinol has the same size and shape as Hypoxanthine (purine), binds to active site/receptor, blocking action of Xanthine Oxidase enzyme to produce urates which have inflammatory complications in joints (Gout)
When referring to medications to patients, which of the following nomenclature should be used?
A. Chemical Name
B. Non-proprietary/Generic Name
C. Official Name
D. Brand Name
Non-proprietary/Generic Name
Example: Paracetamol, rather than Panadol
What are the major ways that drugs can be named?
Plant name or Chemistry
What are the way drugs can be classified?
Chemical Group
Function
Target
International Nonproprietary Names
What is the International Nonproprietary Names given for anesthetics?
Drug name that ends in -caine
What is an example of a non-specific target for drugs?
Antacid preparations to neutralise H+ in stomach acid
What are 3 examples of specific drug targets?
Protein (very common)
RNA/DNA (less common)
Lipid cell membrane (uncommon)
What are 3 targets of drug action located on the cell surface?
Membrane bound receptors (very common) Ion channels Carrier proteins (pumps/transporters)
What are 3 intracellular targets of drug action?
Enzymes (very common)
RNA/DNA (cell nucleus)
Protein
A low Kd (dissociation constant) is indicative of what?
A low molar concentration needed for drug to work. Therefore the drug has a high affinity for the target receptor
A high Kd (dissociation constant) is indicative of what?
A high molar concentration needed for drug to work. Therefore the drug has a low affinity for the target receptor
What is the dissociation constant for a drug?
concentration at which 50% of binding sites (receptors) are occupied by drug
Would effects would there be if a drug had a similar high affinity for more than one target receptor?
Different action on a the different site
Outcome could be either helpful or an unintentional side effects
What is the preferred pharmacopoeia for dental prescribing?
Australian Medical Handbook (AMH) 2016
Therapeutic Guidelines 2012 (v2): Oral and Dental
MIMS is unreliable and not practical
What is Pharmacodynamics?
Effect of the Drug on the Body:
The pharmacological response or functional change in the body resulting from interaction of drug on the body
What is Pharmacokinetics?
Effect of the Body on the Drug:
Absorption Distribution Elimination: excretion/metabolism Factors which alter the concentration of drug in body: disease, age, other drugs, genetics Used to design drug dosage
What is Toxicology?
The discipline dealing with undesirable effects of xenobiotics
What is an example of a non-specific drug target?
Antacid preparations to neutralise H+ in stomach acid
Which is more common: specific or non-specific drug tagets?
Specific Drug Targets
What are the 3 types of Specific Drug Targets?
Protein (very common)
RNA/DNA (less common)
Lipid cell membrane (uncommon)
What are the main classes of targets for drug action?
- Cell Surface Targets (Membrane Bound Receptors, Ion Channels, Carrier Proteins)
- Intracellular Targets (Enzymes, RNA/DNA, Proteins)
What are the sites of action for drugs targeting intracellularly?
Enzymes (very common)
RNA/DNA (cell nucleus)
Protein
What are the sites of action for drugs targeting the cell surface?
Membrane bound receptors (very common) Ion channels Carrier proteins (pumps/transporters)
What is a Ligand?
A substance (in this instance drug) that binds with a biomolecule for a functional purpose. Drugs are typically ligands that bind with receptors to induce a functional change (eg with Opioid or Adrenergic Receptors)
Would it be beneficial if a drug had a similar high affinity for more than one target receptor??
Probably not, it could have a helpful/unintentional side effects, or completely different action on a the different site
Example: Hay fever medication - additional high affinity to salivary glands induces dry mouth
What is drug affinity?
How tight the protein binds to the drug. Higher affinity requires lower molar concentration of the drug to work
What is the dissociation constant (Kd)?
The concentration at which 50% of binding sites (receptors) are occupied by drug
What is the clinical implication for drug prescribing for a drug with a low Kd?
A Low Kd drug is 50% dissociated at a lower molar concentration, making it a high affinity drug. Therefore a lower dosage is needed for the drug to work
What is the clinical implication for drug prescribing for a drug with a high Kd?
A Low Kd drug is 50% dissociated at a higher molar concentration, making it a lower affinity drug. Therefore a higher dosage is needed for the drug to work
Do small conformational changes in molecular shape/orientation affect the drug’s affinity?
Yes.
Codeine vs Morphine are almost chemically identical with the only difference a OH vs CH3O group, but yet have enormous difference in drug affinity.
Codeine Kd = 150nm (Weak Analgesic) vs Morphine ( Kd = 1000nm) (Strong Analgesic)
How do ligand-gated channels work?
Ligand binds to a binding domain on the channel, opening the channel for ion flow
How do voltage gated channels work?
Coordinated depolarisation (voltage change) triggers a ion channels to open
What types of ion efflux are common in drug action?
Cl-, Na+, K, H+, Ca2+
T/F: Local Anesthetics work as channel openers
False: they work as channel blockers
Local Anesthetics block sodium transduction and prevents membrane depolarisation and subsequent action potential
T/F: benzodiazepines, diazepam, oxazepam work as Channel Openers
True: they work as channel opener
What are the 2 mechanisms that a channel opener can have?
- Prolong duration of channel opening
2. Increase frequency of channel opening
What are the 3 types of carrier pumps
- Uniporters
- Antiporters
- Symporters
How does a Uniporter carrier pump work?
Facilitate transport of only one solute across the cell membrane
How does a Antiporters carrier pump work?
Facilitate transport of two dissimilar solutes in opposing direction across the membrane
How does a Symporters carrier pump work?
Facilitate transport of two dissimilar solutes in the same direction across the membrane
What type of carrier pump is involved with Diuretics, and how do they work on the kidney?
Symporter: diuretic drug blocks the Na/Cl symporter, increasing the sodium gradient into the distal tubule of the kidney. Water follows the sodium gradient to increase urine excretion
What is the role in diuretics in treating high blood pressure
Increasing excretion of urine decreases blood volume that decreases MAP.
What type of carrier pump is involved with anti stomach ulcer / reflux drugs?
Antiporter: Proton Pump Inhibitors (eg Omeprazole) inhibit H+/K+ exchange, so in turn decrease stomach lumen concentration of H+. This reduces the damaging effects of acid in stomach ulcers and acid reflux
What is the mechanism of action of SSRI-antidepressants?
- SSRIs antidepressants close membrane transports found on the end of the presynaptic neuron
- This limits re-absorption of serotonin into the presynaptic cell
- This increases the concentration of serotonin in synaptic cleft to bind to postsynaptic receptor
- People with depression typically have depressed levels of serotonin - this in effect allows for normal firing of neurons
What are 3 examples of drug classes that target enzymes?
- NSAIDS: anti-inflammatories
- ACE Inhibitors: address high blood pressure
- HMGCoA Reductase Inhibitors (Statins): address high LDL cholesterol
What is the difference in length of duration of competitive vs irreversible drugs
Irreversible: drug covalently binds to site, therefore inactivating enzyme. Therefore, the only way the body can recover is to create new enzymes.
This means the duration will be longer
What are the complications of aspirin being an irreversible inhibitor of cyclooxygenase (Cox) in platelets
Aspirin induces complete irreversible inhibition of cyclooxygenase (Cox) in platelets, therefore limiting platelet aggregation.
If this was an issue with treatment, the patient would have to wait 1 week after stopping aspirin in order for the body to synthesise new cyclooxygenase
What is the current clinical advise with regard to aspirin and post surgical bleeding complications
Risk of bleeding is less than the beneficial effect of preventing heart attack.
Warn patient of chance of bleeding for some time
Apply other hemostatic agents during surgery
Monitor patient for safety after treatment
A Ligand gated ion channel blocker for a nicotinic acetylcholine receptor would have what effect?
- Prevent Acetylcholine from binding to Ion Channel
- Prevents influx of sodium
- Depolarisation can’t occur
- No skeletal muscle Contraction
Would you expect drugs that work on 2nd Messengers to work immediately?
No, onset would occurs in minutes.
Ion Influx from 1st Messengers require action from intracellular enzymes
Would you expect drugs that work on Intracellular Nucleic receptors to work immediately
No, onset would be in hours as gene transcription/translation is involved
Would you expect drugs that work on Intracellular Nucleic receptors to keep working after the patient has ceased use of the drug?
Yes, RNA has already been altered, so RNA stimulation is still ongoing and Protein translation will still occur
Would you expect an Asthma preventer (Corticosteroid) to treat an acute asthma attack?
No, it’s action is slow as it alters transcription of inflammatory mediators. It would not provide immediate relief or target action on smooth muscle tissue on the lungs
What type of medication is an asthma reliever?
Salbutamol: bind to beta 2 receptor (G-protein coupled receptor)
Quick effect that is has affinity to beta 2 receptors: causes smooth muscle tissue in the lungs to dilate.
What are the 2 classes of asthma therapy drugs?
- Relievers (Selective Beta 2 agonists)
2. Preventers (Corticosteroids)
How can we quantify and classify the effect of a drug?
- Size of Response
- Reversibility of Action
- Graded-Dose Response Relationship
Dose Concentration/Effect work on a linear or log scale?
Typically a linear scale
What is ED50 and why is this significant
It is the dosage required to get 50% efficacy OR where 50% of people have 50% of max effect (Essentially the same thing)
A drug that reaches ED50 at a lower 5mg dosage is far more potent
What is the issue with a drug that has a very steep dose concentration/effect curve?
A small increase in concentration (where the curve is steepest) leads to a very large increase in response: making the risk of adverse effects/toxicity higher
T/F: 2 Drugs that work on the same target receptors will follow the same Dose-Response Curve Slope
True, as there are limited number of receptors of the same type to bind to
T/F: 2 Drugs that work on the different target receptors will follow the same Dose-Response Curve Slope
False, the drugs are independent of each other and will follow different slopes
Would you expect full agonist to reach 100% effect of a Dose-Response Curve Slope
Yes
Would you expect partial agonist to reach 100% effect of a Dose-Response Curve Slope
No, by definition a partial agonists are drugs that bind to and activate a given receptor, but have only partial efficacy at the receptor relative to a full agonist. It can not reach 100% effect
What is the Therapeutic Index?
The Toxic Dose / Effective Dose
High TI = toxic dose if substantially bigger than normal dose
Low TI = only a small increase in dose produces toxic effects
The interaction between St John’s wart and Cyclosporine is an example of what?
Altered Pharmacokinetics: St John’s Wart speeds up the metabolism of cyclosporine and other drugs, reducing it below a efficacious concentration = increasing risk of organ transplant failure.
What is the role of Cyclosporine?
It is an immunosuppressant drug that prevents organ transplant rejection
What are the dental side effects of Cyclosporine?
Gingival Hyperplasia
Dosage regimen is a vital part of pharmacokinetics. What are the 4 dosage regimen considerations when prescribing a drug?
- Route of administration (e.g. oral)
- Amount (dose)
- Frequency (how often)
- Duration (for how long)
What is the main measurement of an optimal drug concentration and why is this chosen?
Blood plasma concentration
- Good correlation with target site concentration
- Easy to access and test
What 4 factors influence the administered drug dose to the end blood concentration?
Absorption
Distribution
Metabolism
Excretion
Why might drug response differ between individuals?
Pharmacokinetic factors (Absorption, Distribution, Metabolism, Excretion) all affected by:
Age Weight Disease (type and severity) Genetic Environment Interaction with drugs
Why is there less difference in drug response in animals tests than human trials?
- Less genetic variability in lab rat populations
- Very controlled environment: housing, food all same
What are different pharmacokinetic parameters that can chart drug plasma concentration over time?
Bioavailability (f)
Clearance (CL)
Volume of distribution (V)
Half-life (t ½)
What is the Therapeutic window?
The optimum drug concentration at the site of action to ellicit the desired effect
Too Low: No Effect
Too High: Toxicity
Which is more desirable: a wide or narrow therapeutic index window?
Wide Therapeutic Window: the jump in dosage between effective dose and toxicity / no effect is very large.
This means there is less risk in patients being able to suffer from dosage issues despite interpersonal variation in pharmakinetics
Why would the route of administration of a drug for acute and chronic disease be different?
Acute Disease: requires rapid response and quick bioavailability
Chronic Disease: may opts for a slow release administration route so there is less intervention needed by the patient for regular dosage
What are the 2 factors to consider when deciding on the route of drug administration?
- Properties of the Drug
2. Therapeutic Objective: Rapid response vs Chronic Dosage
What are 3 enteral drug administration sites?
- Oral (Tablets, Capsules, Mixtures)
- Sublingual
- Rectal (Suppositories)
What are the benefits of administering drugs sublingually as opposed to orally?
Drug avoids liver first pass
Some drugs they are completely metabolised by the liver so can’t enter the bloodstream (Glyceryl Trinitrate for Angina)
What are the benefits of administering drugs rectally as opposed to orally?
- If the illness is causing vomiting
2. Also partially avoids liver first pass
What is the most direct Parenteral drug administration route?
Intravenous Injection - results in very rapid onset at target tissue
What is the difference between aqueous solutions and oily suspensions used in intramuscular injections into skeletal muscle?
Aqueous solution → slow absorption
Oily suspension → very slow absorption
What are indications for a parenteral administration route?
- Poorly absorbed drugs
- Drug unstable in acid stomach
- Unconscious patient
- Can’t swallow orally
- Need very quick onset (IV only)
What are alternative non enteral or parenteral drug administration routes?
Inhalers Intranasal Topical Creams/Oiltments Transdermal Patches Eye Drops Ear Drops
T/F: Transdermal Patches are very slow acting drug delivery vehicles that are intended for systemic effects
True
What administration route does not involve Drug Absorption?
All types except for I/V injections:
Oral: Tablet, Capsule, Liquid Sublingual Transdermal Rectal Intramuscular / Subcutaneous Injection Inhalers, Intranasal, Eye, Nose, Ear
What is Drug Absorption?
Process by which drug proceeds from site of administration to site of measurement (blood stream) within the body
What are the mechanisms of Drug Absorption in the GIT?
- Passive Diffusion
2. Carrier Mediated Update Transport
T/F: Lipophobic drugs are absorbed faster via passive diffusion
False, fat solubility is the key factor in rapid movement via the cell membrane.
Lipophobic (aka souble) drugs typically require Carrier Mediated Uptake Transport but are rate limited by the number of transporter located on the cell surface.
Therefore they are slower than lipophillic drugs that can freely move through the cell membrane
What are the properties of movement of drug molecules via passive diffusion?
- Movement from high to low concentration gradients
- No energy required for movement
- No saturation
- No competitive inhibition
What is Octanol/water partition ratio (O/W) used for?
It is a water solubility measure for estimation of drug distribution within the body
Lipophilic/Hydrophobic drugs
have O/W > 5 = high permeability / absorption
Example: codeine
Lipophobic/Hydrophillic drugs
O/W < 1 = low permeability/adsorption
Example: antibiotics
What is the clinical implication for dosage for Lipophobic drugs?
Typically require a far higher dosage as they have low cellular permeability/absorption
Why is taking large dosages of water soluble vitamins a waste of time?
Permeability of hydrophillic/lipophobic drugs on the cell membrane is rate limited by the number of efflux pump transporters (Carrier Mediated Uptake Transport) that can transport the drug at any time.
Any excess dosage not transported is simply excreted
What is the main purpose of Carrier Mediated Uptake Transports?
To support transport of very water soluble drugs
What are the properties of movement of drug molecules via carrier mediated uptake transports?
- Energy is Required
- Transports can be saturated
- Transports can be specific
- Competition for Transport can occur
What is P-glycoprotein (Pgp) an example of, and what is it’s function?
P-glycoprotein (Pgp) is a transmembrane glycoprotein that functions as efflux pump to push xenobiotics out of a cell.
In terms of drug absorption, it can pushes xenobiotics/toxins back into the intestinal lumen, thus acting as a protective mechanism against potentially toxic substances in our diet
What are the 3 physiological factors that impact on GIT absorption?
- Blood Flow
- Large Surface Area
- Gastric Emptying
Is blood flow typically a limiting factor in drug absorption?
Typically no: most drugs are not sufficiently fat soluble, therefore slow absorption via the GIT is what prevents it from taking effect
However, highly fat soluble drugs are rapidly absorbed (eg alcohol). In this instance, blood flow is the rate limiting factor in reaching the brain
How is surface area important in GIT absorption?
Microvilli in the small intestine provide 1000x more surface area than the stomach, meaning there are more surface cells to allow for absorption. This is why most drugs enter via the intestine and not the stomach.
Why is Gastric Emptying required for absorption?
Affects the speed/rate of absorption
If you’re backed up, the drug can’t be absorbed along GIT
How can a patient increase absorption via gastric emptying?
- Take a dump
2. Consume the drug with 250ml of water
What are different ingredients in oral medication designed to maximise absorption?
- Filler
- Lubricant
- Disintegration Agents: to correct disintegrate the tablet to maximise solution being absorbed, but not to be destroyed in the stomach
- Enteric Coating: to resist acid dissolution in the stomach
Why would a Sustained Release Tablets/Capsules be designed?
Reduce rate of dissolution
Reduce rate of absorption
Reduce frequency of dosing (helps in pt compliance)
What is the method of administration that would maximise drug bioavailability?
Intravenous Injection
What factors reduce bioavailability?
- Insufficient time for absorption (lipophobic/requires activity transport)
- Decomposition in gut lumen (Acid Hydrolysis, Complexation, Efflux Transport Out, Metabolism by Gut Wall)
- Hepatic first pass effect: liver metabolises/excretes much of the drug, reducing bioavailability
What are the 3 determinants for Drug Distribution?
- Rate of blood flow to tissue/organ
- Ability to cross the cell membrane wall
- Binding to plasma and tissue proteins
What are the 2 ways drugs can be transported in systemic circulation?
- Unbound/Free Drug
2. Protein Bound Drug
What determines the rate/speed of drug distribution in the blood stream?
- Blood flow to the organ - well perfused organs take up drugs more easily
- Protein Bounded Drugs: can’t cross small capillaries
- Blood Brain Barrier
What is volume of distribution a measure of?
The drugs ability to be distributed to target tissues
Volume of Distribution (V) = Amount in body (A) / Blood Concentration (C)
High V = High Tissue Binding (readily absorbed)
Low V = Low Tissue Binding (only low quantity is absorbed, most excreted)
What are the 2 routes of Drug Elimination?
- Metabolism: conversion to another chemical in the liver
2. Excretion: loss of a chemically unchanged drug via the kidney