Drug interactions
Chlorpheniramine + Olanzapine / samidorphan
Severity: Moderate
Chlorpheniramine and Olanzapine / samidorphan: moderate interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Both chlorpheniramine and olanzapine have anticholinergic activity, and olanzapine also causes sedation. Combined use can increase constipation, urinary retention, dry mouth, blurred vision and drowsiness, and in severe cases gastrointestinal hypomotility.
What this interaction means in plain words
Chlorpheniramine and Olanzapine / samidorphan can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Why it happens
Additive antimuscarinic and sedative effects from H1 and muscarinic receptor antagonism.
What to do
Monitor for constipation, urinary retention and sedation, and treat bowel symptoms early. Prefer a non-sedating, non-anticholinergic antihistamine where possible.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Chlorpheniramine
Frequently asked questions
Can I take Chlorpheniramine with Olanzapine / samidorphan?
MediHelp rates the interaction as moderate. Chlorpheniramine and Olanzapine / samidorphan can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Both chlorpheniramine and olanzapine have anticholinergic activity, and olanzapine also causes sedation. Combined use can increase constipation, urinary retention, dry mouth, blurred vision and drowsiness, and in severe cases gastrointestinal hypomotility.
How serious is the interaction between Chlorpheniramine and Olanzapine / samidorphan?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor for constipation, urinary retention and sedation, and treat bowel symptoms early. Prefer a non-sedating, non-anticholinergic antihistamine where possible.
What other medicines interact with Chlorpheniramine?
MediHelp also lists interactions of Chlorpheniramine with, for example, Belladonna and opium, Benzhydrocodone / acetaminophen, Brexanolone. The full list is on the Chlorpheniramine page.
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