SynthesisBMJ open2014
Meta-analysis: the effects of smoking on the disposition of two commonly used antipsychotic agents, olanzapine and clozapine.
Synthesis in BMJ open, 2014. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 48 papers, 2 of them syntheses that pooled it.
What it found
Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.
The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.
Who cites it
48 citing papers in PubMed, 2 syntheses or guidelines pooled it, 117 citations in OpenAlex.
- Saliva Based Clozapine Therapeutic Drug Monitoring: A Systematic Review.Pharmacology research & perspectives · 2025Pooled it
- Clinical, Biochemical and Genetic Variables Associated With Metabolic Syndrome in Patients With Schizophrenia Spectrum Disorders Using Second-Generation Antipsychotics: A Systematic Review.Frontiers in psychiatry · 2021Pooled it
- Clearing the smoke: experiences of patients and professionals during a one-year smoking cessation intervention in ambulatory mental healthcare - a qualitative study.Substance abuse treatment, prevention, and policy · 2025Trial
- Association between body mass index and serum concentrations of olanzapine and selective serotonin reuptake inhibitors in patients with eating disorders.European journal of clinical pharmacology · 2026Article
- 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.Neuropsychopharmacology reports · 2026Article
- Clinical importance of the 5-Step Precision Medicine (5SPM) method in shared decision-making to choose the antipsychotic treatment for a patient with first-episode psychosis: a case report.BMC psychiatry · 2026Article
- Trajectories of Clozapine Concentrations in Women Across Menopausal Age.Schizophrenia bulletin · 2026Article
- The Impact of Sex and Age on Antipsychotic Serum Concentrations.Schizophrenia bulletin · 2026Article
- The evolving landscape of pharmacogenomics: Current achievements and future directions.Pharmacological reviews · 2026Review
- Treating hearts and minds: adverse cardiovascular effects of psychiatric medications.Therapeutic advances in drug safety · 2026Review
- Nicotine Misuse and Treatment of Schizophrenia Exacerbations in Men: An Observational Study in Poland.Pharmaceuticals (Basel, Switzerland) · 2025Article
- Puff and psychosis: a retrospective cohort analysis of psychiatric hospitalisations in patients with schizophrenia and nicotine use.BMJ open · 2025Article
- QT Interval, Antipsychotics and Correlates Among Patients with Schizophrenia: Cross-Sectional Data from the Multicentric Real-World FACE-SZ.Drug safety · 2025Article
- UnidentifiedJournal of psychopharmacology (Oxford, England) · 2024Article
- Polygenetic risk scores and phenotypic constellations of obsessive-compulsive disorder in clozapine-treated schizophrenia.European archives of psychiatry and clinical neuroscience · 2024Article
- Increased antipsychotic drug concentration in hospitalized patients with mental disorders following COVID-19 infection: a call for attention.Frontiers in psychiatry · 2024Article
- Association of clozapine and norclozapine levels with patient and therapy characteristics-focus on interaction with valproic acid.European journal of clinical pharmacology · 2023Article
- Association of smoking cigarettes, age, and sex with serum concentrations of olanzapine in patients with schizophrenia.Biochemia medica · 2023Article
- Outcomes Among People With Schizophrenia Participating in General-Population Smoking Cessation Treatment: An Observational Study.Canadian journal of psychiatry. Revue canadienne de psychiatrie · 2023Observational
- Deep Learning Methods Applied to Drug Concentration Prediction of Olanzapine.Pharmaceutics · 2023Article
Corrections and comments
PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.
Authors and funding
3 authors at 2 institutions in 1 country.
Funding
No grant is acknowledged in the PubMed record.
Abstract
objectiveTo clarify the effects of smoking on the disposition of two commonly used antipsychotics, olanzapine and clozapine, and to create standards to adjust the doses of these drugs in clinical practice based on the smoking status.
designA meta-analysis was conducted by searching MEDLINE, Scopus and the Cochrane Library for relevant prospective and retrospective studies. INCLUDED STUDIES: We included the studies that investigated the effects of smoking on the concentration to dose (C/D) ratio of olanzapine or clozapine. PRIMARY OUTCOME MEASURE: The weighted mean difference was calculated using a DerSimonian-Laird random effects model, along with 95% CI.
resultsSeven association studies, comprising 1094 patients (652 smokers and 442 non-smokers) with schizophrenia or other psychiatric disorders, were included in the meta-analysis of olanzapine. The C/D ratio was significantly lower in smokers than in non-smokers (p<0.00001), and the mean difference was -0.75 (ng/mL)/(mg/day) (95% CI -0.89 to -0.61). Therefore, it was estimated that if 10 and 20 mg/day of olanzapine would be administered to smokers, about 7 and 14 mg/day, respectively, should be administered to non-smokers in order to obtain the equivalent olanzapine concentration. Four association studies of clozapine were included in the meta-analysis of clozapine, comprising 196 patients (120 smokers and 76 non-smokers) with schizophrenia or other psychiatric disorders. The C/D ratio was significantly lower in smokers than in non-smokers (p<0.00001), and the mean difference was -1.11 (ng/mL)/(mg/day) (95% CI -1.53 to -0.70). Therefore, it was estimated that if 200 and 400 mg/day of clozapine would be administered to smokers, about 100 and 200 mg/day, respectively, should be administered to non-smokers.
conclusionsWe suggest that the doses of olanzapine and clozapine should be reduced by 30% and 50%, respectively, in non-smokers compared with smokers in order to obtain an equivalent olanzapine or clozapine concentration.
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Registered trials
Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.