In a first-episode psychosis pilot, “olanzapine monotherapy” described the antipsychotic regimen. It did not mean that participants received olanzapine alone. Nine of the 23 patients in the analysis were listed with a benzodiazepine prescription. That distinction matters when using the study to interpret symptoms or adverse effects during treatment.
What the study actually measured
Zabala and colleagues examined a single olanzapine plasma concentration about two months after treatment began. They drew samples an average of 11 hours after dosing and included patients with quantifiable olanzapine. The paper reported an association between psychotic symptom response and a range of measured concentrations, but the proposed concentration cutoffs had poor specificity. The study did not find an association between olanzapine concentration and the severity of adverse effects in this small sample.
Where benzodiazepines fit
Fifteen participants received other nonantipsychotic medications. Among them, three were listed with benzodiazepines alone as adjuncts, four with benzodiazepines plus an antidepressant, one with a benzodiazepine and folic acid, and one with a benzodiazepine and lithium. Some patients were listed with more than one benzodiazepine. A prescription identifies a potential exposure. The olanzapine plasma test establishes neither a benzodiazepine concentration nor the timing of any benzodiazepine dose.
How to read the evidence in a case file
The pilot did not estimate the independent contribution of benzodiazepines to symptoms, sedation or other adverse effects. If a report cites the study as evidence about a patient’s presentation, ask what the author means by monotherapy, which drug the laboratory measured, and which other prescriptions or administered doses were documented. See also how the type of plasma evidence limits a diazepam assay study.
Source: Zabala A and colleagues. Journal of Clinical Psychopharmacology. 2017, 37:569–577. doi:10.1097/JCP.0000000000000770.
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