Background and Importance Olanzapine is an atypical antipsychotic that is metabolised by the cytochrome P-450 (CYP1A2 isoenzyme). This isoenzyme is induced by tobacco smoke, resulting in reduced plasma concentrations of olanzapine when both are administered concomitantly.
Aim and Objectives The aim is to analyse and compare the daily dose of olanzapine and its plasma concentration in smoking and non-smoking patients.
Material and Methods Retrospective observational study of patients on chronic treatment with olanzapine, whose levels were monitored in the clinical pharmacokinetics area of the Pharmacy Service of a regional hospital between 01/01/2021 and 08/06/2021.The daily doses administered, age, sex and results of plasma monitoring were consulted by accessing their clinical records. Therapeutic range of olanzapine considered: 20–80 mcg/mL. To evaluate the effect of CYP1A2 isoenzyme induction, the mean concentrations obtained were compared with those that should theoretically be present in the group of smokers according to the linear dose-concentration pharmacokinetic behaviour of olanzapine in non-smokers.
Results Sixty-two patients were monitored, five were excluded (four for undetectable levels and one for a self-harm attempt), so that the analysis finally included 57 patients in total: 17 smokers (29.8%) and 40 non-smokers (70.2%). 21 women (36.8%): 9 smokers and 12 non-smokers; 36 men (63.2%): 8 smokers and 28 non-smokers. Median age: 44 years (IQR=31.5–54.5).
For the mean olanzapine dose observed in women and men smokers, the mean theoretical concentration would have been 83.5 mcg/mL in women and 61.3 mcg/mL in men. This is 37.1% and 18.8% higher than the results obtained, respectively.
Conclusion and Relevance In the smokers group, the mean prescribed dose was 3.3% higher in women and 18.2% higher in men, and the mean plasma concentration was 35% lower in women and 0.6% lower in men, compared to the non-smokers group.
Differences were observed between smokers and non-smokers that would correspond to the tobacco-inducible effect, although studies with larger numbers of patients are needed to establish the tobacco-olanzapine interaction as clinically relevant.
Conflict of Interest No conflict of interest.
Statistics from Altmetric.com
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.