Clozapine and Olanzapine interaction
Clozapine and Olanzapine: both prescribing labels flag this combination with the strongest language, such as a contraindication, a boxed warning, or an instruction to avoid it.
Do not combine without a prescriber's guidance. The label language below is the strongest FDA uses.
What the FDA labels say
From the Clozapine (Clozaril) label · effective 2025-06-06
Proportion of Adult Subjects in Schizophrenia Studies with Weight Gain ≥7% Relative to Baseline Body Weight Weight change CLOZARIL Olanzapine Chlorpromazine N 669 442 155 ≥7% (inclusive) 236 (35%) 203 (46%) 13 (8%) 5.11 Neuroleptic Malignant Syndrome Antipsychotic drugs including CLOZARIL can cause a potentially fatal symptom complex referred to as Neuroleptic…
When possible, avoid concomitant use, with other anticholinergic medications because the risk for anticholinergic toxicity or severe gastrointestinal adverse reactions is increased [see Warnings and Precautions ( 5.7 ), Drug Interactions ( 7.1 )].
• Anticholinergic Toxicity : When possible, avoid use with other anticholinergic drugs and use with caution in patients with a current diagnosis or prior history of constipation, urinary retention, clinically significant prostatic hypertrophy, or other conditions in which anticholinergic effects can lead to significant adverse reactions.
Use with caution in patients with a current diagnosis or prior history of constipation, urinary retention, clinically significant prostatic hypertrophy, or other conditions in which anticholinergic effects can lead to significant adverse reactions.
An increased risk cannot be excluded for CLOZARIL or other antipsychotics or other patient populations.
From the Olanzapine (Zyprexa) label · effective 2026-02-11
Anticholinergic (antimuscarinic) Effects: Use with caution with other anticholinergic drugs and in patients with urinary retention, prostatic hypertrophy, constipation, paralytic ileus or related conditions.
Taking more than these two? Interactions stack. Check your whole list at once; it stays in your browser.
Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.