antipsychotic
5 interactions related to antipsychotic
smoking + clozapine
Polycyclic aromatic hydrocarbons in tobacco smoke (not nicotine) potently induce CYP1A2, the enzyme responsible for roughly 70% of clozapine metabolism, lowering clozapine plasma levels by up to 50% in smokers. Sudden smoking cessation can cause clozapine levels to rise 50-72% within 3-5 days, risking sedation, seizures, and toxicity.
smoking + olanzapine
Polycyclic aromatic hydrocarbons in cigarette smoke induce CYP1A2, the primary enzyme that metabolizes olanzapine, increasing olanzapine clearance by roughly 37-48% in smokers. Meta-analysis data suggest olanzapine doses should be 30% lower in non-smokers than in smokers to reach the same plasma levels.
grapefruit + lurasidone
Lurasidone is primarily metabolized by CYP3A4 and is highly sensitive to CYP3A4 inhibitors. The FDA-approved Latuda prescribing information specifically states that grapefruit and grapefruit juice should be avoided in patients taking lurasidone because they inhibit CYP3A4 and can substantially raise lurasidone concentrations.
grapefruit + quetiapine
Quetiapine is metabolized primarily by CYP3A4. Grapefruit juice inhibits intestinal CYP3A4 and can substantially increase quetiapine plasma concentrations; a documented case report describes quetiapine toxicity in a young woman who consumed a gallon of grapefruit juice over 24 hours while on a stable dose.
caffeine + clozapine
Caffeine inhibits CYP1A2, the main enzyme that metabolizes clozapine. High caffeine intake (especially energy drinks) can dramatically raise clozapine levels, with case reports of life-threatening toxicity including multiorgan failure.