PK PD And Calculation

Question 1

Give three reasons why modified release preparations are made.

Answer 1

Reduce side effects of the drug
To prolong duration of therepeutic action
Reduce dosing for better adherence

Question 2

Describe the difference in reactions carried out by Phase I and Phase II enzymes.

Which phase are CYP enzymes found?

Answer 2

Phase I - oxidation, dealkylation, hydrolysis, reduction
Phase II - conjugation

Phase I

Question 3

What is the affect of grapefruit on CYP?

Answer 3

Inhibits CYP3A4

Question 4

Give some routes for drug elimination.

Answer 4

Kidney 
Biliary 
Faecal 
Sweat
Genital secretions
Saliva
Breasts milk

Question 5

What is the effect of GFR on half life?

Answer 5

Increased GFR decreases half life

Decreased GFR increases half life

Question 6

What can be said about half life of first order kinetic drugs?

Answer 6

Remains constant

Question 7

Name 3 drugs which show zero order kinetics.

Answer 7

Phenytoin
Alcohol
Aspirin

Question 8

How do you calculate loading dosage?

Answer 8

Loading dose = (Vd x desired conc in plasma)/ bioavailability