Pharmacology

Question 1

Define pharmacokinetics and pharmacodynamics.

Answer 1

Pharmacokinetics = what the body does to the drug

Pharmacodynamics = what the drug does to the body

Question 2

What are the four main targets for drug action?

Answer 2

Receptors
Enzymes
Transporters
Ion channels

Question 3

Define ligand.

Answer 3

Ligand = substance that forms a complex with a biomolecule to serve a biological purpose

Question 4

Define receptor.

Answer 4

Receptor = proteins interacting with extracellular physiological signals and converting them to intracellular effects

Question 5

List the main receptors in order of the speed of their action, from fastest to slowest.

Answer 5

Ligand-gated ion channels -> G-protein-coupled receptors -> Kinase-linked receptors -> Nuclear receptors

Question 6

Define a full agonist.

Answer 6

Able to generate maximal response after binding to receptor (high affinity and high intrinsic activity)

Question 7

Define a partial agonist.

Answer 7

Drug that has an intrinsic activity of less than 1. Receptor occupancy produces a submaximal effect

Question 8

Define an inverse agonist.

Answer 8

Drug binds and exerts an opposite effect to endogenous agonist

Question 9

Define an antagonist.

Answer 9

Exhibits affinity but no intrinsic activity

Question 10

What is the formula for therapeutic index?

Answer 10

TI = maximum non-toxic dose / minimum effective dose

Question 11

What are the four methods of pharmacokinetic drug disposition?

Answer 11

Absorption
Distribution
Metabolism
Excretion

Question 12

What are the factors affecting rate of transfer of drugs across membranes?

Answer 12

Diffusion coefficient
SA of tissue
Membrane thickness
Partition coefficient
Conc. gradient

Question 13

Define bioavailability.

Answer 13

Bioavailability = fraction of a dose reaching the systemic circulation after admin compared to same dose administered intravenously

Question 14

What is the formula for apparent volume of distribution?

Answer 14

Apparent volume of distribution = amount of drug administered / plasma conc.

Question 15

What are the five factors determining drug distribution?

Answer 15

Protein binding
Tissue binding
Organ blood flow
Membrane permeability
Drug solubility

Question 16

Define clearance.

Answer 16

Clearance = volume of plasma from which drug is completely removed per unit time

Question 17

Define half-life.

Answer 17

Half-life = time taken for plasma conc. to fall to 50% of its initial value

Question 18

What are the two phases of hepatic drug metabolism?

Answer 18

Phase I - convert drug to more polar metabolite

Phase II - conjugation with substrates

Question 19

Which hepatic metabolic pathway do cats lack, and what is the effect of this?

Answer 19

The glucuronidation pathway.

Longer effects and accumulation of drugs e.g. anaesthetics

Question 20

What is the enterohepatic circulation loop?

Answer 20

Drug metabolism (e.g. glucuronidation) -> Biliary excretion -> Deglucuronidation by gut microflora -> Reabsorption from gut ->

Question 21

Define bacteriostatic and bacteriocidal.

Answer 21

Bacteriostatic = arrest bacterial multiplication

Bacteriocidal = act primarily by killing bacteria

Question 22

What are the three mechanisms of chemotherapy action?

Answer 22

Cell wall - interferes with maintenance of bacterial cell wall

Cytoplasmic membrane - interferes with structure of plasma membrane

Nucleic acid metabolism - interferes directly with microbial DNA or its replication or repair