Pharmacology Flashcards
What is pharmacology
Study of drug action on the body
What is pharmacokinetics
The study of what the body does to a drug
What is pharmacodynamics
Physiological effects of a drug on the body
What does ADME mean in pharmacokinetics
Absorption
Distribution
Metabolism
Excretion
If a drug is given orally, where does it go
GI tract
What happens when a drug is absorbed by the GI tract
Goes to the liver where some drugs are broken down
How can elimination happen
Broken down by liver
Excreted by kidneys
Excreted via lungs
Where does pharmacological action happen
Circulation tissue space
What is absorption
Rate and extent at which a drug leaves its site of administration and enters the circulatory system
What can impede the efficacy of a drug
Route of administration e.g. orally or rectally
What can enhance or impair the rate of absorption
Presence of food
What happens when the GI tract is compromised
A parenteral route must be considered
Why does location of drug administration need to be considered
Tissue perfusion will also impact on absorption
What is first pass effect
When a drug has been absorbed into circulation it is transported to the liver via hepatic portal system where it is metabolised
Why do we have to reduce the amount of active drug being distributed within the body
Because some drugs undergo extensive hepatic metabolism
What is produced by first pass effect
Drug and metabolites
How can first pass effect be avoided
Using parenteral route which bypasses this process and provides body with a more accurate dosage
Once a drug has been metabolised by the liver, where does it go
Enters the systemic circulation and travels in the plasma to its site of action
What happens once a drug has reached the desired site of action
It leave the plasma and enters interstitial fluid then the cells and combines cellular receptors to create an action
What affects drug distribution
Drug formulation
Blood flow to that area
Binding/unbinding of the drug to plasma proteins
Presence of anatomic barriers
What are fat loving drugs
Lipophilic
What are water loving drugs
Hydrophilic
Which route of administration is best for hydrophilic drugs
IV, IM as they enter the extra cellular fluid
Which route of administration is best for lipophilic drugs
Orally or SC as needs rap diffuse through a cell membrane
When are drugs most rapidly distributed. Give examples
When entering well perfused tootsies e.g. active skeletal muscle, liver, kidney, brain
Which tissues are poorly perfused
Inactive skeletal muscle and adipose fats
What remains in the circulation as a reservoir for circulating drugs
Plasma proteins
What happens when a drug binds with a plasma protein (albumin)
Termed inactive and unable to migrate into the tissues to exert its effect
What happens to drugs that do not bind to plasma proteins
Able to migrate into tissues and exert effect
What happens to the amount of unbound and bound drug after plasma protein binding
Drug within circulation will remain the same
What happens to bound molecules when unbound drug molecules move into tissues during plasma protein binding
Bound molecules are released to maintain the balance
Why is protein binding significant
Because plasma protein levels are reduced due to disease as the standard dose could cause toxic concentrations
Which organs can cause toxic concentrations of drugs
Liver, GI, kidney
Why are anatomical barriers important
In the capillaries of the CNS as endothelial cells in the brain are closely packed together preventing some drugs from entering
What type of drugs can cross the blood:brain barrier
Lipophilic
What happens to drugs before they can be excreted
Biotransformation / drug metabolism
Where does bio transformation happen
Generally in liver (lungs and kidneys)
What happens when drugs are metabolised
Enzymes modify the molecules of the drug to enable elimination
What does enzyme action do during metabolism
Provokes chemical reactions that cause drug to become hydrophilic enabling drug to be eliminated by kidneys
Factors affecting drug metabolism
Species, age, nutritional status, health status
Where does excretion take place
Liver, lungs, skin, glands e.g. mammary, sweat and salivary
Why does excretion route need to be taken into consideration
Could compromise effectiveness of excretion when specific organ is diseased
Why is pharmacokinetics important
Formulates suitable drug dose and dosing regime to facilitate therapeutic effect
Pharmacokinetic parameters:
Bioavailability
Volume of distribution
Clearance and half life
What is bioavailability
The quantity of the administered drug reaching systemic circulation
When is bioavailability reduced greatly from 100% IV
When given orally
What is volume of distribution
Measurement relating to the amount of drug absorbed within the plasma, body tissues and cells
What properties of a drug affect a drugs ability to distribute
Interaction with plasma proteins, drug for me.g, hydrophilic or lipophilic
What is clearance
Volume of blood cleared of a drug from eliminating organ e.g. liver, kidneys
What is important when devising a drug regime for a patient regarding clearance
To enable suitable serum drug concentrations. Must be equal to the rate of drug administration
What is half life
Time it takes for drug to be reduced by 50% at current concentration level
What can greatly affect the plasma concentration of a drug
Efficacy of kidneys and liver as half life will take longer to decrease
Why is pharmacodynamics important
Ensured indication for using specific drug has been discussed and any contraindications have been evaluated
What to cellular receptors normally interact with regarding drug-receptor interaction
Endogenous Ligands
What are endogenous ligands
Natural substances e.g hormones and neurotransmitters
How does a drug exert its effect
By binding to a protein receptor found in the cell membrane, cytoplasm or nucleus
What is affinity
Ability of a drug to bind to receptor
What is efficacy
Ability of a drug to produce the desired effect
What is an agonist
Drug that has good affinity and efficacy
What is an antagonist
Drug that has poor affinity and efficacy
What is the therapeutic effect
Effect of a drug within an Animals body to control a specific disease or manage physiological function. The narrow dosage parameter a drug has to remain in, to enable therapeutic effect to be efficient
What happens when therapeutic range is too high
May produce toxic effect. MSC: maximum safe concentration or MTC: minimum toxic concentration
What happens when the therapeutic range is too low
Prevents the desired effect and termed minimum effective concentration (MEC)
How long does a prescription last for
6 months for normals drugs. Can be on repeat
28 days for controlled drug. Cannot be on repeat
Requirements for POM-V
Once prescribed by VS who is confident the person using it is competent to do so.
Drug will have safety issues or concerns, deemed that specialist knowledge is required, drug has narrow safety margins and is government policy
Requirements for POM-VPS
Registered qualified person e.g. vs, pharmacist or SQP. Prior clinical assessment is not prerequisite
Requirements for POM-V (CD)
Dispensed once prescribed by VS
Drug access must be by person deemed confident by vs to handle
VS will have key
Pros for oral administration of medication for owners
Easy for most owners
Cons for oral administration of medication
Slow compared to parenteral
Not suitable for unconscious/vomiting patient
Food can impact on administration
Can cause irritation (V/D)
Gastric acid can denature drugs
Liver enzymes may break down drugs before it reaches systemic circulation
Pros of parenteral administration of medication
Directly into systemic circulation therefore 100% bioavailability
Drug action achieved quickly
Drugs can irritate skin
Cons of parenteral administration of medication
Requires asepsis Must be solution Must be given slowly Irritant drugs can cause severe tissue damage Catheter care
Pros of IM administration of medication
Can be suspended drug
Absorbed quicker than SC
Cons of IM medication administration
small volumes at a time
2ml in cats
5ml in Dogs
Pros of SC administration of medication
Can be large amounts of fluid
Generally pain free
Cons of SC medication administration
Multiple sites should be used for high volumes of fluid to avoid discomfort
Possible damage to small blood vessels
Local reaction to drug can occur
Where do you admin IM injections and how long does it take
Quadriceps of hindlimb takes 20-30 minutes
How long does SC injection take to work
30-45 minutes
What is intaosseous
Injection into bone marrow in medulla of long bone; when IV is compromised e.g. birds
What is epidural
Aseptic technique of injecting into vertebral canal outside the duramater
What is intrarthecal
Aseptic technique of injection into subarachnoid space containing cerebrospinal fluid; contrast media for myelography
Subconjunctiva
Into conjunctival membrane of eye
Legal requirements to f dispensing label for medication
- Name and address of animal and owner
- Name and address of approved premises supplying the medication
- Date of supply
- The words ‘keep out of reach of children’
- The words ‘for animal treatment only’
Discuss the cascade system
- Veterinary medicinal produce authorised in the UK for another condition in the same species or another species with the same condition
- Medicinal product authorised in uk for human use or veterinary product authorised in eu member state for use in animal species
- Veterinary product made by vs, pharmacologist or person holding manufacturers authorisation as prescribed by vs
Key information given to clients when dispensing medication
- Technique demonstration e.g. using pill guns, filling syringes and tube feeding.
- Specific requirements for drug e.g. before food
- Potential side effects/contraindications and client told to phone if this happens
- Told when to stop medication and told to return an medication if necessary
- Person dispensing should be confident client is happy doing what is expected
Requisition requirements for schedule 2 drugs
Made in writing to supplier, signed by vs
Storage requirements for schedule 2 drugs
Locked cabinet secured to wall or floor
Destruction must take place in front of authorised person
Invoices kept for 2 years
Dispensing requirements for schedule 2 drugs
Drug register kept with all purchases and each supply within 24 hours
Requisition requirements for schedule 3 drugs
Made in writing to supplier, signed by vs (same as schedule 2)
Schedule 2 drugs
Morphine
Pethidine
Fentanyl
Ketamine
Storage requirements for schedule 3 drugs
Locked cabinet
Invoices kept for 2 years (same as schedule 2)
Dispensing requirements for schedule 3 drugs
No register
Examples of schedule 3 drugs
Pentobarbital
Phenobarbital
Buprenorphine
Tamazepam
Requisition requirements for schedule 4 drugs
Prescription bed by MRCVS
Storage requirements for schedule 4 drugs
None
Dispensing requirements for schedule 4 drugs
Prescribed by MRCVS but should be checked. Can be dispensed by SQP/vet/nurse as long as checked
Examples of schedule 4 drugs
Benzodiazepines
Anabolic steroid
Examples of schedule 5 drugs
Coedine
Morphine (in less than specified amounts)
What does p.o or per os mean
By mouth
What does a.c mean
Before food
What does p.c mean
After food
What does q. Mean
Every
What does p.r.n mean
As necessary
What does a.s mean
Sufficient quantity
