Antiepileptics: Valproate, Carbamazepine, Phenytoin

Key points

• Sodium valproate: first-line generalised epilepsy; side effects — teratogenicity (neural tube defects), weight gain, tremor, hair loss, hyperammonaemia, PCOS association.
• Carbamazepine: first-line focal epilepsy; P450 inducer; side effects — diplopia, ataxia, hyponatraemia, Stevens-Johnson syndrome (esp. HLA-B*1502).
• Phenytoin: zero-order (saturable) kinetics — small dose increases can cause toxicity; side effects — gum hypertrophy, hirsutism, megaloblastic anaemia, cerebellar signs in toxicity.
• All are teratogenic — folate supplementation pre-conception; valproate particularly associated with neural tube defects.

Decision points in this pathway

• Phenytoin levels rising unexpectedly?

The full step-by-step algorithm, including what to do at each branch, opens in the app for approved members.