antipsychotic
5 interactions related to antipsychotic
smoking + clozapine
Polycyclic aromatic hydrocarbons in tobacco smoke (not nicotine) strongly induce CYP1A2, the liver enzyme that handles most clozapine metabolism, so smokers tend to have lower clozapine levels and need higher doses. The greater danger is stopping smoking: levels can climb sharply over a few days as the enzyme returns to baseline, risking sedation, seizures, and toxicity unless the dose is reviewed.
smoking + olanzapine
Polycyclic aromatic hydrocarbons in cigarette smoke induce CYP1A2, the main enzyme that breaks down olanzapine, so smokers clear the drug faster and run lower blood levels. When someone quits, levels rise over the following days to weeks and side effects can emerge on a previously stable dose. The effect is driven by combustion products, not nicotine.
grapefruit + lurasidone
Lurasidone is metabolized almost entirely by the CYP3A4 enzyme, which makes it highly sensitive to CYP3A4 inhibitors. The FDA-approved Latuda prescribing information states that grapefruit and grapefruit juice should be avoided in patients taking lurasidone, because they inhibit CYP3A4 and can raise lurasidone concentrations.
grapefruit + quetiapine
Quetiapine is metabolized primarily by CYP3A4. Grapefruit juice irreversibly inhibits intestinal CYP3A4 and can substantially increase quetiapine plasma concentrations. A published case report describes quetiapine toxicity in a young woman who consumed a large volume of grapefruit juice over a single day while on a stable dose, with sedation, low blood pressure, and ECG changes that resolved once the juice was stopped.
caffeine + clozapine
Caffeine and clozapine are both broken down by the liver enzyme CYP1A2, and caffeine competitively inhibits it. Large changes in caffeine intake - especially starting or stacking energy drinks - can raise clozapine to toxic levels, with a documented case report of severe toxicity and multiorgan failure.