Anticonvulsants (antiseizure medicines): prescribe for the seizure type
Antiseizure medicines (ASMs) reduce seizure recurrence; they do not cure every cause of a seizure. Safe treatment begins with classification of seizure type, exclusion of acute symptomatic causes, counselling about adherence and safety, and one clear plan for titration and review. Choose monotherapy when possible and do not stop an effective ASM suddenly.
Urgent rule
A convulsive seizure lasting ≥5 minutes, repeated seizures without recovery, respiratory compromise, pregnancy-related seizure, serious injury or persistent altered consciousness is an emergency. Give ABCDE care and follow the local status-epilepticus protocol; this article is not a substitute for emergency orders.
1. Mechanisms and matching drug to syndrome
| Mechanistic group | Examples | Clinical point |
|---|---|---|
| Sodium-channel modulation | Carbamazepine, phenytoin, lamotrigine | Often useful in focal-onset seizures; some may worsen particular generalised seizure types. |
| Enhance GABA activity | Benzodiazepines, phenobarbital, valproate | Useful in acute seizures or selected long-term settings; sedation/respiratory depression matter. |
| SV2A modulation | Levetiracetam | Few interactions but may cause irritability, agitation or mood change; renal clearance needs attention. |
| Calcium-channel effects | Ethosuximide, valproate | Ethosuximide is mainly for absence seizures, not broad “convulsion treatment.” |
WHO recommends lamotrigine or levetiracetam as first-line monotherapy for focal-onset seizures; for generalised onset seizures, lamotrigine, levetiracetam or valproate may be options in men/boys and women/girls not of childbearing potential. In women and girls who may become pregnant, lamotrigine or levetiracetam are preferred first-line options because valproate carries substantial fetal risk.
2. Common maintenance doses: adult teaching table
| Medicine | Typical initiation / titration | Key monitoring and warnings |
|---|---|---|
| Levetiracetam | Common adult start 500 mg orally twice daily; increase gradually (often by 500 mg twice daily every 2 weeks) to response. Typical maximum 1,500 mg twice daily in many labels. | Adjust for renal impairment. Ask about irritability, depression, aggression and suicidal thinking. |
| Lamotrigine | Must be titrated slowly; schedule depends on whether valproate or enzyme-inducing ASMs are also used. | Stop and assess urgently for rash, mucosal lesions, fever or systemic symptoms (SJS/TEN risk). Never use a generic fast titration schedule when interactions differ. |
| Carbamazepine | Common adult start 100–200 mg once or twice daily; increase gradually. Maintenance often 800–1,200 mg/day in divided doses, product/indication dependent. | FBC, LFT and sodium; rash/SJS, leucopenia, hyponatraemia. Strong enzyme inducer—review contraception, anticoagulants and many other drugs. |
| Sodium valproate | Dose is weight- and formulation-dependent; common adult total maintenance range is about 600–2,000 mg/day in divided or modified-release dosing. | Major teratogenic/neurodevelopmental risk; avoid in pregnancy potential unless no suitable alternative and a formal risk-prevention pathway is used. Monitor LFT/FBC; watch weight, tremor, thrombocytopenia, pancreatitis. |
| Phenytoin | Maintenance often around 300 mg/day but has nonlinear kinetics; dose changes must be small and guided by clinical response/levels where used. | Check interactions, albumin/renal context when interpreting levels, gingival hyperplasia, ataxia, rash and bone health. |
| Phenobarbital | Maintenance is protocol- and weight-dependent. | Sedation, cognitive effects, respiratory depression, dependence and enzyme induction; do not stop abruptly. |
3. Status epilepticus: the treatment sequence
- 0–5 minutes: ABCDE, protect from injury, time the seizure, check glucose, oxygen/suction, IV/IO access, pregnancy and cause.
- At 5 minutes: give a benzodiazepine by local protocol and monitor ventilation continuously.
- Persistent seizures: give a protocol-directed second-line loading ASM (such as levetiracetam, fosphenytoin/phenytoin or valproate depending on patient factors and local availability).
- Refractory seizures: anaesthesia/critical-care management, EEG where available and urgent search for cause.
Do not copy a loading dose from a maintenance table. Emergency loading depends on weight, route, age, pregnancy, organ function, ECG/respiratory monitoring and the local protocol.
4. Pregnancy, contraception and long-term care
Discuss pregnancy before initiation and at every review. Valproate is a particularly high-risk medicine in pregnancy. Enzyme-inducing ASMs can reduce hormonal-contraception effectiveness; provide a method-specific plan. Prescribe folate according to local guidance, but do not imply it removes ASM fetal risk. Encourage seizure diary, adherence, sleep regularity, avoidance of alcohol/recreational drugs, and advice about bathing, heights, driving, cooking and occupational risks.
5. Adverse effects and withdrawal
All ASMs can cause dizziness, diplopia, sedation, ataxia and falls. New rash, fever, jaundice, severe abdominal pain, easy bruising, suicidal thoughts or marked behavioural change requires prompt review. Abrupt withdrawal can trigger rebound seizures/status epilepticus. If seizure-free and considering withdrawal, involve an experienced clinician and taper gradually with an individual risk discussion.
OSCE checklist
Identify the seizure phenotype; confirm adherence and exact formulation; screen for pregnancy/contraception and interactions; review adverse effects; document renal/liver tests where relevant; give a seizure-safety plan; and state when emergency help is needed. Explain why a seizure medicine cannot be selected from a “one drug for all seizures” list.
