Drug interactions
Chlorpheniramine + Olanzapine
Severity: Moderate
Chlorpheniramine and Olanzapine: 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
The combination can cause greater drowsiness and impaired alertness than either agent alone. Additive anticholinergic effects such as dry mouth, constipation and urinary retention may also occur, with confusion in older patients.
What this interaction means in plain words
Chlorpheniramine and Olanzapine 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.
Chlorpheniramine belongs to Respiratory; Olanzapine belongs to Central Nervous System.
Why it happens
Additive CNS depression through H1 receptor blockade, plus additive antimuscarinic activity.
What to do
Counsel patients about sedation and avoid driving until tolerance is known. Use a non-sedating antihistamine where possible, particularly in the elderly.
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 Olanzapine
Other interactions of Chlorpheniramine
Frequently asked questions
Can I take Chlorpheniramine with Olanzapine?
MediHelp rates the interaction as moderate. Chlorpheniramine and Olanzapine 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. The combination can cause greater drowsiness and impaired alertness than either agent alone. Additive anticholinergic effects such as dry mouth, constipation and urinary retention may also occur, with confusion in older patients.
How serious is the interaction between Chlorpheniramine and Olanzapine?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Counsel patients about sedation and avoid driving until tolerance is known. Use a non-sedating antihistamine where possible, particularly in the elderly.
What other medicines interact with Olanzapine?
MediHelp also lists interactions of Olanzapine with, for example, Amisulpride, Amoxapine, Apomorphine. The full list is on the Olanzapine page.
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