PH3.3 | PH3.3 | Antiseizure Drugs and Uncontrolled Seizure Management — SDL Guide — Summary & Reflection

KEY TAKEAWAYS

Antiseizure drugs are classified by mechanism: Na⁺ channel blockers (phenytoin, carbamazepine, lamotrigine), T-type Ca²⁺ blockers (ethosuximide — absence only), GABA enhancers (phenobarbitone, BZDs), and SV2A binders (levetiracetam). Phenytoin has zero-order kinetics (therapeutic range 10-20 µg/mL); narrow therapeutic window demands monitoring. Valproate is broad-spectrum but a major teratogen (neural tube defects, ASD in offspring) — avoid in pregnancy; prefer lamotrigine/levetiracetam. Ethosuximide = absence only; phenytoin/carbamazepine worsen absence and myoclonic seizures. Status epilepticus management: 1st = IV lorazepam/diazepam; 2nd = IV phenytoin/valproate; 3rd (refractory) = anaesthetic agents (propofol/thiopental) + intubation.

REFLECT

A 22-year-old woman presents to your outpatient clinic with juvenile myoclonic epilepsy (JME). She is on carbamazepine 400 mg BD (prescribed elsewhere). She reports that her morning myoclonic jerks have worsened since starting the drug. She is not pregnant but wants to start a family in 2 years. Walk through your pharmacological reasoning: why has carbamazepine worsened her JME, what drug would you switch her to, and how does her future pregnancy plan influence your choice? What counselling would you provide?