Phenytoin

Question 1

Drug Class

Answer 1

Antiepileptics

Question 2

Active

Answer 2

Phenytoin

Question 3

Indications

Answer 3

Prevents repetitive neuronal discharge by blocking voltage-dependent and use- dependent (inactivated) sodium channels.

Simple/complex partial seizures

Generalised tonic-clonic seizures

Status epilepticus

Question 4

Dose Range

Answer 4

200-500mg daily (initially 4- 5mg/kg daily and increase 30mg every 2 weeks)

Max. 500 mg daily (think label 5)

Question 5

SE’s

Answer 5

all antiepileptics cause ‘RADS’ = rash, ataxia, dizziness, sedation

all adjuvants (gabapentin, lamotrigine, levetiracetam) have labels 1, 9

• n/v
• gum hyperplasia
• acne
• hirsutism
• facial coarsening
• reduced BP
• neurotoxic (drowsiness, tremor, cognitive difficulties visual disturbances)
• agitation
• teratogenic
• picture ugly chick

Question 6

Counselling

Answer 6

Labels: 5, 9, 12+, 13

• Phenytoin may make you feel drowsy or dizzy; if affected, do not drive or operate machinery.
• This medicine may also increase the effects of alcohol.
• Phenytoin interacts with many other drugs; ask your doctor or pharmacist before using any other medicine including herbal and over-the-counter products.
• Visit your dentist regularly; good dental care can help prevent phenytoin causing enlarged gums.
• Tell your doctor immediately if symptoms such as fever, sore throat, rash, mouth ulcers, bruising or bleeding occur (blood dyscrasia).
• Do not stop taking this medicine suddenly unless your doctor tells you to.

Question 7

Monitoring

Answer 7

• phenytoin concentration
• BP, ECG and respiratory function monitoring is recommended during IV use
• BMD monitoring, and vitamin D and calcium supplements to prevent osteomalacia and osteoporosis, in patients on long-term treatment, particularly those at higher risk, eg elderly patients