Pharmacokinetics IV

Question 1

Name FOUR anti-epileptics

Answer 1

Phenytoin
Carbamazepine
Sodium Valproate
Gabapentin

Question 2

What pharmacokinetics does phenytoin exhibit?

Answer 2

Non linear due to binding site saturation

Question 3

What is the distribution of phenytoin?

Answer 3

~90% protein bound

Question 4

What is the metabolism of phenytoin?

Answer 4

Significant metabolism by liver

Question 5

What is the excretion of phentoin?

Answer 5

Very little excreted unchanged

Question 6

State the re-arranged Michaelis-Menton equation for phenytoin

Answer 6

Cp(ss) = Daily dose x Km / V(max) - Daily dose

Question 7

What is the metabolism of lithium?

Answer 7

There is no metabolism

Question 8

What is the excretion of lithium?

Answer 8

Follows first order kinetics

Clearance approximates to 25% creatinine

Question 9

Does theophylline have a salt factor?

Answer 9

Yes

Question 10

What is the metabolism of theophylline?

Answer 10

Metabolised significantly by the liver

Question 11

What is the excretion of theophylline?

Answer 11

<10% is excreted unchanged

Question 12

How does clearance variance change with age?

Answer 12

Initial increase to a peak, followed by a sharp decrease

Question 13

How does clearance variance change with some disease states? (6)

Answer 13

Decrease clearance - Acute pulmonary oedema, congestive heart disease, liver cirrhosis

Increase clearance - Mild smoking, heavy smoking, cyctic fibrosis

Question 14

How does clearance variance change with drug interactions? (6)

Answer 14

Decrease clearance - propanolol, oral contraceptives, cimetidine

Increase clearance - carbamazepine, phenytoin, rifampicin