Pharmacology

Question 1

What is pharmacokinetics and what are the three phases of pharmacokinetics?

Answer 1

The effect that the body has on the drug

1. Absorption
2. Distribution
   
   • one compartment model: even distribution
   • two compartment model: distribution X on first administration, distribution Y at steady state
3. Elimination (metabolism or excretion)

Question 2

What is pharmacodynamics?

Answer 2

The effect that the drug has on the body

Includes Efficacy and Toxicity

Question 3

What drugs inhibit p-glycoprotein?

Answer 3

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Verapamil
Amiodarone
Ketokonazole
Ritonavir
Tacrolimus/Cyclosporin
Antibiotics

Question 4

What drugs induce p-glycoprotein?

Answer 4

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St Johns wort
Rifampin
Dexamethasone

Question 5

What drugs are the substrates of p-glycoprotein?

Answer 5

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Atorvastatin
Tacrolimus
Dabigatran
Rivaroxaban
Losartan
Digoxin
Chemo

Question 6

Formula for working out oral vs IV bioavailability

Answer 6

F = AUCoral/AUCiv

Must be equivalent doses! Eg. Can’t be 100mg oral, 50mg IV

Question 7

What is clearance and how is it calculated?

Answer 7

The volume from which the drug is completely cleared per unit time (volume/time)

Does not equal elimination! And will change with the amount of drug/rate of drug going into the system

Formulas:

Cl = F(bioavailability) x dose/ AUC

Dose rate = plasma steady state concentration x CL

Question 8

What is the difference between zero order and first order kinetics?

Answer 8

Zero order = clearance is constant at the point of saturation
Eg. Alcohol, phenytoin

First order = clearance depends on drug concentration

Question 9

What does OAT do and name one OAT inhibitor

Answer 9

OAT - organic anion transporter

Brings things into the cell (influx)

Can be blocked by probenacid
- stops uric acid being taken up into blood (uricosuric)
- stops penicillin being taken up by renal tubular cell (increased serum penicillin)

Question 10

Which two drug classes are both p-Gp and CYP3A4 inhibitors?

Answer 10

Azoles - ketoconazole etc
Avirs - ritonavir etc

Question 11

Which drug classes are p-Gp and CYP3A4 inducers?

Answer 11

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Carbamazepine
Phenytoin
St. John’s wort
Rifampicin

Question 12

What is the formula for renal clearance

Answer 12

Cl(renal) = UV/P

U = urine drug concentration
V = urine volume
P = plasma drug concentration

Question 13

What is the formula for concentration at steady state

Answer 13

Css = DR x F/Cl

DR = dose rate
F = bioavailability
Cl = clearance