Session 2 - Pharmacodynamics and Pharmacokinetics 2

Question 1

What is a partial agonist?

Answer 1

Agonist cannot enact 100% response. When in solution with an agonist can act as a competitive antagonist

Question 2

What is drug Specificity and drug selectivity?

Answer 2

Specificity - Targets only one subtype of a receptor e.g. beta2

Selectivity - Targets all types of a particular receptor e.g. beta receptors

Question 3

What is affinity?

Answer 3

Tendency of a drug to bind to a specific receptor type

Question 4

What is efficacy?

Answer 4

Ability of a drug to produce a response as a result of receptor being occupied

Question 5

What is potency?

Answer 5

Dose required to produce the desired biologic response

Question 6

How do you calculate the therapeutic index of a drug?

Answer 6

EC50 (adverse effect) / EC50 (desired effect)

Question 7

How do you calculate the Vd?

Answer 7

Vd = Dose/[Drug]t0

Question 8

What effect does grapefruit juice have on enzymes?

Answer 8

Inhibits several CYP450 isoenzymes

Question 9

What effect does cranberry juice have on enzymes?

Answer 9

inhibits CYP2C9 isoform enzyme

Question 10

How can liver failure impact on drug clearance?

Answer 10

Increased half life, less enzymes

Question 11

How can cardiac disease impact drug clearance?

Answer 11

Reduced organ perfusion of liver and kidneys

Question 12

How does renal failure impact drug clearance?

Answer 12

Less quickly eliminated through waste

Question 13

How would you calculate the loading dose necessary for a drug?

Answer 13

Loading dose = Vd x [drug]target

Question 14

What is the relationship between half life of drug and volume of distribution?

Answer 14

Higher volume of distribution = higher half life

Question 15

How does the multi compartment model affect drug clearance?

Answer 15

Drug can be excreted from different compartments (muscle, fat, plasma) at different rates

Question 16

What are the main routes of administration via the enteral route?

Answer 16

oral, rectal, sublingual

Question 17

What are the primary parenteral routes?

Answer 17

intravenous, intra-arterial, intramuscular, intrathecal, subcutaneous

Question 18

What are the pros and cons of enteral?

Answer 18

pros - cheaper, easier to use, can self administer

cons - drug can be metabolised, slower onset, irritates GI, unsuitable if vomiting (oral)

Question 19

What are the pros and cons of parenteral?

Answer 19

Pros - quick onset, no degradation, dosing can be exact

Cons - must be sterile, requires HCPs, more expensive, unconvenient

Question 20

What are the pros and cons of transdermal delivery?

Answer 20

Pros - steady rate of drug delivery, avoid breakdown by liver

Cons - Suitable only for lipid soluble drugs, relatively expensive

Question 21

Some drugs work at a concentration in the plasma that approaches total saturation of the serum albumin. Why would increasing the dosage of such a drug have a disproportionate effect on the body?

Answer 21

Only the unbound molecules are active. Increasing drug conc when total saturation has reached would result in far more unbound molecules than in previous increases of drug conc

Question 22

How does the blood flow through adipose tissue affect uptake of drugs into adipose?

Answer 22

Body fat has a low blood supply and therefore when drugs are administered acutely only very lipid soluble drugs will partition siginificantly into fat.

However, when a drug is administered chronically then levels of that drug can build up over time in the fat stores

Question 23

What pH drug does albumin mainly bind?

Answer 23

Acidic drugs

Question 24

What 2 factors concerning the drug itself determine the rate of drug absorption from the intestine?

Answer 24

Lipid solubility and ionisation

Question 25

Define bioequivalence

Answer 25

2 drugs that are expected to act in a very similar way