Pharmacology Flashcards
Define Pharmacology
The science/study of drugs and their effects on a living organism
Define Pharmacokinetics
The movement of the drug and what happens when it enters the body.
- Absorption
- Distribution
- Metabolism
- Excretion
Define Pharmacodynamics
The effect that the drug has on the body- what does it do to the body?
What are the routes of administration?
- Subconjunctivial
- Oral or ‘per os’
- Intratracheal
- Nebulization
- Intravenous
- Inhalation
- Subcutaneous
- Topical (Skin, nose, eyes)
- Epidural
- Rectal
- Intramuscluar
- Intraosseous
- Intra-articular
- Intracardiac
- Intraperitoneal
- intradermal
What are the routes of excretion?
- via the urinary tract
- faeces
- bile
- breath (anaesthetic)
- saliva
What is the Cascade System?
When administrating a medicine you should use one that has obtained an marketing authorisation for that species and condition.
If there is not one available or if it doesn’t exist, select a product which treats the condition in another species. This is known as ‘off-label’ use.
If no such product exists, select a product authorised for human use or a veterinary product in an EU member of state (not the UK).
if no such product exists, use a product prepared by an authorised person. This is known as ‘special order’ products.
What is the difference between a generic name and a trade name?
Generic name- the concise name given to a specific chemical compound e.g. Fipronil
Trade name- the name by which the drug is marketed
e.g. Frontline
What is a drug?
A chemical that has a known biological effect on a living organism
How do drugs work?
Drugs produce their effects through their actions on different cells of the body. Particular molecules, known as receptors, within the cell combine with the drug to initiate a response. Drugs reduce the activity of enzymes and modify the their actions through the ion channels.
Drug absorption and distribution- what is diffusion?
Simple diffusion is where drug molecules pass across the gastro-intestinal mucosa from an area of high concentration to an area of low concentration.
Drug absorption and distribution- what is active transport?
Energy is used to transport the drug molecules from the gastro-intestinal tract to the bloodstream.
As energy is used this means that the drug can move from an area of low concentration to an area of high concentration, going against the concentration gradient.
What do drug molecules within the systemic circulation bind to?
Proteins
Highly bound protein drugs have…
Less free drug molecules – therefore higher doses are needed.
What are natural barriers?
Blood-brain barrier and placenta
What factors can affect absorption rate?
- The physical and chemical characteristics of the drug (hydrophilic or lipophilic)
- lipid solubility
- amount of blood flow to the intended organ
- route of administration
- amount of albumin in the blood
What is bioavailability?
The amount of drug that enters the circulation intact/unaltered.
How do drugs distribute?
Drugs move through the circulation by binding to plasma proteins (Albumin) or being dissolved in blood lipid. They then go to there intended target organ. This is known as the therapeutic affect.
What happens when drugs interfere with the liver?
An increase in enzymes decrease the efficacy of drugs, increasing the risk of toxicity.
What is the term for the metabolisation of drugs?
Biotransform
What happens during drug metabolism?
Occurs in the liver (biotransform), the drug is changed into a from which can be excreted form the body. Drugs may need to be metabolised through the use of ACE inhibitors. Enzymes alter the structure of the drug by hydrolysis, reduction and oxidation
What is Enteral administration and give an example of a drug administrated via this route
A drug absorbed by the GI tract and then circulated around the body after being administrated orally such as Sucralfate
What is Topical administration and give an example of a drug administrated via this route
Applying a drug directly to the skin, eyes, ears or mucous membranes. Emodepside and anthelmintic are used to treat local conditions.
What is Parenteral administration and give an example of a drug administrated via this route
Any other route except the GI tract- usually injectable
What considerations are there when deciding the best administration route?
- some routes may endanger the animal
- the drug can be destroyed if not administrated the proper route
- can harm certain conditions
- patient temperament
- speed of reaction needed
- convenience to person administrating
What happens to a drug once it has been administrated orally?
Travels through the GI tract, enters the hepatic portal vein, liver removes toxic substances (first pass effect), solid drugs then dissolve before reaching systemic circulation. Often results in slow release.
What is the absorption rate of a drug administrated IV?
0-2 mins
What is the absorption rate of a drug administrated IM?
20-30 mins
What is the absorption rate of a drug administrated S/C?
30-45 mins
What is the absorption rate of a drug administrated Orally?
Dependant on the type and coating of the tablet
What is tissue perfusion and how does it affect the rate of absorption?
Directly affects the rate of absorption and influenced by vasoconstriction and vasodilation. It is the passing of fluid through the circulatory or lymphatic system to a target organ.
