Berm E J J Lisette, Ruijsbroek Rianne, Loonen Anton J M, Goethals Kris R, Wilffert Bob, van Hasselt Fenneke
Rijksuniversiteit Groningen, afd. Farmacie, basiseenheid Farmacotherapie en Farmaceutische patiëntenzorg, Groningen.
Ned Tijdschr Geneeskd. 2015;159:A9090.
Cytochrome P450 subtype 1A2 (CYP1A2) is responsible for the metabolism of several drugs, including the antipsychotic agent clozapine. Smoking cigarettes induces CYP1A2. Due to this induction, a higher dosage of the drug is required by patients who smoke tobacco.
The dosage of clozapine was changed for a 34-year-old male because of suspected active psychosis. However, serum levels of clozapine did not change according to expectations. It appeared that the patient had switched from smoking normal cigarettes to using e-cigarettes and then started smoking cigarettes again during the time of the dosage change. This gave a plausible explanation for the observed clozapine concentrations.
When patients switch from smoking normal cigarettes to using e-cigarettes induction of the CYP1A2 enzyme stops. A switch of this type may result in a major, undesirable increase in drug concentrations. Doctors should be alert to this when prescribing medication metabolised by CYP1A2 with a narrow therapeutic window.
细胞色素P450 1A2亚型（CYP1A2）负责多种药物的代谢，包括抗精神病药物氯氮平。吸烟会诱导CYP1A2。由于这种诱导作用，吸烟的患者需要更高剂量的药物。
一名34岁男性因疑似急性精神病而调整了氯氮平的剂量。然而，氯氮平的血清水平并未如预期那样变化。看来该患者在剂量调整期间从吸普通香烟改为吸电子烟，之后又重新开始吸普通香烟。这为观察到的氯氮平浓度提供了一个合理的解释。
当患者从吸普通香烟改为吸电子烟时，CYP1A2酶的诱导作用停止。这种转变可能导致药物浓度大幅且不良地升高。在为治疗窗较窄的由CYP1A2代谢的药物开处方时，医生应警惕这一点。
