Phenytoin

Question 1

Phenytoin indications

Answer 1

Tonic clonic seizures
Focal seizures
Status epilepticus

Question 2

What do we know about pheytoin’s pharmacokinetics?

Answer 2

They are non-linear

Question 3

What is phenytoin’s therapeutic range?

Answer 3

10 to 20 mg/L

Question 4

What are the signs of toxicity?

Answer 4

Slurred speech
Nystagmus
Ataxia
Confusion
Hyperglycaemia
Double vision
SNACHD

Question 5

What monitoring requirements are neede?

Answer 5

LFT, FBC, Folate, Vit D
IM use: ECG and BP

Question 6

What are the important actions to remember with phenytoin?

Answer 6

1. report any signs of toxicity
2. Stay on the same brand
3. Risk of death with IM use
4. Pregnancy prevention
5. Risk of suicidal thoughts

Question 7

What are the drug interactions with Phenytoin?

Answer 7

Hepatotoxic drugs
CYP inducers
CYP inhibitors
Drugs that lower seizure threshold
Anti-folates

Question 8

What are the non-specific side effects of phenytoin?

Answer 8

Depression and suicide
Hepatotoxicity
Hypersensitivity
Blood dyscrasia’s
Vitamin D deficiency –> bone pain

Question 9

What are the specific side effects of phenytoin?

Answer 9

Coarsening appearance
Facial hair

Question 10

What effect does phenytoin have on cyp enzyme substrates?

Answer 10

It’s an enzyme inducer