Phenytoin

Question 1

Use of phenytoin?

Answer 1

Treatment of epilepsy (all except absence) and neuropathic pain

Question 2

Phenytoin desired serum concentration

Answer 2

10-20mg/L

Narrow therapeutic index

Question 3

Phenytoin monitoring?

Answer 3

FBC, Liver function test

Question 4

Phenytoin side effects (8)

Answer 4

N+V
Constipation
Gingival hypertrophy,
Rash
Acne
Hirsutism
Coarse faeces
Blood/Skin disorders

Question 5

Pt counselling phenytoin

How to take?

Answer 5

Look for signs of blood/skin disorders - Fever, sore throat, rash, mouth ulcers, bruising, bleeding, leucopenia

Take with or after food

Question 6

Phenytoin

Answer 6

NSAIDS - enhances effect of phenytoin

Amiodarone - inhibits metabolism of phenytoin - toxicity

Warfarin - Phenytoin accelerates metabolism of warfarin - higher bleed

Cimetidine - inhibits metabolism of phenytoin - toxicity

Fluoxetine - Increases plasma conc. of phenytoin

St Johns Wort - reduces plasma conc. of phenytoin