Effects of Repeated Smoking and Quitting Cigarettes on Plasma Concentrations of Clozapine and Its N-Desmethyl and N-Oxide Metabolites in a Japanese Patient With Schizophrenia.

Smoking → CYP1A2 induction → increased clozapine metabolism → low plasma levels. Cessation → de-induction → rising concentrations → toxicity risk

This case report documents in a Japanese clozapine patient plasma concentration variations of clozapine and its metabolites (N-desmethyl, N-oxide) during repeated cycles of smoking resumption and cessation. CYP1A2 de-induction during smoking cessation leads to a significant and progressive rise in clozapine concentrations, with toxicity risk if monitoring is not adapted. This case concretely illustrates the CYP1A2 phenoconversion mechanism in a real clinical context.

Synthesis written by Geno'X. For the full original abstract, please refer to the source publication.

The single case limits statistical power, but the kinetic illustration of smoking/cessation cycles on clozapine concentrations is pedagogically valuable. CYP1A2 phenoconversion by smoking is known but under-monitored in practice — this report reminds us that any change in smoking status in a clozapine patient should trigger dose adjustment.

Clinical impact: 2/3 · Evidence strength: 1/3 · Novelty: 1/2 · Sample size: 0/1 · Publication status: 0/1 → Total: 4/10