Major
Quetiapine × Rifampicin
Atypical antipsychotics×Antituberculous antibiotic
Mechanism
Rifampicin is the most potent CYP3A4 inducer available. Quetiapine plasma levels fall 5- to 8-fold – clinical inefficacy of the antipsychotic.
Symptoms
Return of positive symptoms: hallucinations, delusions, agitation. In bipolar disorder: manic episode risk.
Management
During anti-TB therapy, increase quetiapine 5-fold with clinical monitoring. Alternative antipsychotics without CYP3A4 dependence: olanzapine or aripiprazole. Alternative anti-TB drug: rifabutin (weaker CYP3A4 induction).