Drug interactions
Amantadine + Trimethoprim
Severity: Moderate
Amantadine and Trimethoprim: 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
Trimethoprim can reduce renal tubular secretion of amantadine, raising its plasma concentrations. Case reports describe amantadine toxicity with confusion, myoclonus and hallucinations, especially in older patients or those with reduced renal function.
What this interaction means in plain words
Amantadine and Trimethoprim 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.
Amantadine belongs to Anti Virals; Trimethoprim belongs to Anti Bacterial.
Why it happens
Competition for renal tubular cation transport, reducing amantadine clearance.
What to do
Monitor for neurotoxicity and reduce the amantadine dose in renal impairment; consider an alternative antibiotic in high-risk patients.
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?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Amantadine and Trimethoprim, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 14 days on the web. No card needed.
Other interactions of Amantadine
- Amantadine + Ethanol Major
- Amantadine + Memantine-donepezil Major
- Amantadine + Metoclopramide Major
- Amantadine + Metoclopramide intranasal Major
- Amantadine + Amifampridine Moderate
- Amantadine + Amisulpride Moderate
Other interactions of Trimethoprim
Frequently asked questions
Can I take Amantadine with Trimethoprim?
MediHelp rates the interaction as moderate. Amantadine and Trimethoprim 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. Trimethoprim can reduce renal tubular secretion of amantadine, raising its plasma concentrations. Case reports describe amantadine toxicity with confusion, myoclonus and hallucinations, especially in older patients or those with reduced renal function.
How serious is the interaction between Amantadine and Trimethoprim?
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 neurotoxicity and reduce the amantadine dose in renal impairment; consider an alternative antibiotic in high-risk patients.
What other medicines interact with Amantadine?
MediHelp also lists interactions of Amantadine with, for example, Ethanol, Memantine-donepezil, Metoclopramide. The full list is on the Amantadine page.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
