Major
Carbamazepine × isotretinoin
Antiepileptics. Carboxamide derivatives×Systemic retinoid (vitamin A derivative)
Mechanism
Carbamazepine is a CYP3A4 inducer. It lowers isotretinoin plasma levels, which can cause acne therapy failure. Additionally: both drugs are teratogens, absolutely contraindicated in pregnancy.
Symptoms
Recurrence of acne, no response to isotretinoin. In pregnancy on combination: severe foetal malformations (both drugs are teratogens).
Management
Avoid the combination. Alternative anticonvulsants without induction: levetiracetam, lamotrigine. Alternative acne therapy: antibiotics (doxycycline, azithromycin), topical retinoids, spironolactone in women. In women of reproductive age, mandatory dual contraception.
Check the full regimen, not just this pair
Opens the checker with these two drugs prefilled. Add the rest of the regimen and recompute additive risks.