Major
Carbamazepine × Haloperidol
Antiepileptics. Carboxamide derivatives×First-generation antipsychotics. Butyrophenone derivatives
Mechanism
Carbamazepine induces CYP3A4 – a partial haloperidol clearance route. Haloperidol plasma levels fall by 50% and antipsychotic effect weakens.
Symptoms
Return of positive symptoms: hallucinations, delusions, agitation. In schizophrenia, risk of acute relapse.
Management
During carbamazepine therapy, increase haloperidol 1.5- to 2-fold under clinical monitoring. Alternative anticonvulsants without induction: sodium valproate, levetiracetam, lamotrigine (no CYP3A4 induction).