Drug interactions
Amitriptyline + Sulfamethoxazole
Severity: Moderate
Amitriptyline and Sulfamethoxazole: 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 agents have been linked to QT prolongation, and co-trimoxazole has been reported to cause torsades de pointes in at-risk patients. Amitriptyline adds to this risk.
What this interaction means in plain words
Amitriptyline and Sulfamethoxazole 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 effects on cardiac repolarization, with sulfamethoxazole-trimethoprim effects on potassium channels and electrolytes also possible.
What to do
Check an ECG and electrolytes, particularly in patients with other QT risk factors. Choose a non-QT-prolonging antibiotic if the risk is high.
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 Amitriptyline
- Amitriptyline + Isocarboxazid Contraindicated
- Amitriptyline + Methylene blue Contraindicated
- Amitriptyline + Phenelzine Contraindicated
- Amitriptyline + Pimozide Contraindicated
- Amitriptyline + Procarbazine Contraindicated
- Amitriptyline + Safinamide Contraindicated
Frequently asked questions
Can I take Amitriptyline with Sulfamethoxazole?
MediHelp rates the interaction as moderate. Amitriptyline and Sulfamethoxazole 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 agents have been linked to QT prolongation, and co-trimoxazole has been reported to cause torsades de pointes in at-risk patients. Amitriptyline adds to this risk.
How serious is the interaction between Amitriptyline and Sulfamethoxazole?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Check an ECG and electrolytes, particularly in patients with other QT risk factors. Choose a non-QT-prolonging antibiotic if the risk is high.
What other medicines interact with Amitriptyline?
MediHelp also lists interactions of Amitriptyline with, for example, Isocarboxazid, Methylene blue, Phenelzine. The full list is on the Amitriptyline page.
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