Viva

Question 1

Define pharmacokineties

Answer 1

what the body does to a drug

Question 2

define pharmacodynamics

Answer 2

what the drug does to the body

Question 3

what is clearance?

Answer 3

the volume of plasma cleared of a drug per unit of time

Question 4

what is half-life?

Answer 4

time taken for drug concentration to decline to half it’s original value

Question 5

what is half-life of a drug dependent on?

Answer 5

volume of distribution

clearance

Question 6

what is volume of distribution?

Answer 6

the volume into which a drug will distribute into

• high if lipid soluble
• lower if water soluble

Question 7

what are first order kinetics?

Answer 7

refer to drugs where clearance is proportional to plasma concentration

• most drugs

Question 8

what are zero order kinetics?

Answer 8

clearance is not always proportion to plasma concentration

occurs at saturation of metabolism (constant rate of elimination regardless of plasma level due to all enzymes used)

e.g. phenytoin, salicylates, ethanol

Question 9

what is bioavailability?

Answer 9

% reaching systemic circulation

100% in IV

Question 10

when is a loading dose needed?

Answer 10

loading doses are used to reduce the time needed to reach a steady state of drug level

good if short or long half life
examples are phenytoin, digoxin, amiodarone, theophylline

Question 11

what is first pass metabolism?

Answer 11

inactivation of drug prior to systemic circulation in gut wall + liver
e.g. propranolol, verapamil, morphine, nitrates

Question 12

how are drugs excreted?

Answer 12

either:
- phase 1 metabolism -> renal excretion
- phase 2 metabolism -> renal excretion

Question 13

what is phase 1 metabolism?

Answer 13

Creation of reactive, polar functional groups

• Oxidation: usually by CyP450 system
• Reduction and hydrolysis

Question 14

what is phase 2 metabolism?

Answer 14

Production of polar compounds for renal elimination

• Either the drug or its phase 1 metabolite
• Conjugation reactions
• Glucuronidation, sulfonation, acetylation, methyl

Question 15

describe cytochromeP450 system

Answer 15

Most important system of phase 1 metabolism
> 11 subtypes

CyP3A4 - Most important subtype
≥ 30% of drugs: CCBs, β-B, statins, benzos

CyP2D6 - Second most important
≥20% of drugs: antidepressants, some β-B,
opiates

Question 16

what drugs are affected by varying acetylation?

Answer 16

Fast vs. slow acetylators (↑↑ fast in Japan vs. Europe)

Affects: isoniazid, hydralazine and dapsone

Question 17

what are the allergy types in relation to medications?

Answer 17

1 - allergy/anaphylaxis, IgE

2 - cytotoxic Ab resulting in haemolysis e.g. penicillin, methyldopa, oral hypoglycaemics

3 - immune complex - serum sickness, penicillins

4 - cell-mediated (T), topical treatments

Question 18

classification of adverse drug reactions?

Answer 18

A - common, predictable, dose-related, consequence of known pharmacology

B - rare, idiosyncratic, not dose related, include pharmacogenetic + allergy

Long term ADR - dependence, addiction, withdrawal, adaptive changes (tardive dyskinesia)

delayed ADR - carcinogenesis, teratogenesis

Question 19

p450 inducers

Answer 19

Phenytoin
Carbamazepine
Barbiturates
Rifampicin
Alcohol (chronic)
Griseofulvin
St. John’s Wart

Question 20

p450 inhibitors

Answer 20

Valproate
INH
Protease inhibitors
Cipro, Cimetidine
Erythromycin + clarithromycin
Omeprazole
Grapefruit juice
Fluconazole / Fluoxetine