Terbinafine and Tamsulosin Interaction
Drug interaction information between Terbinafine and Tamsulosin.
Terbinafine and Tamsulosin have a documented moderate interaction in FDA labeling.
FDA drug labeling documents a moderate-severity interaction between Terbinafine and Tamsulosin. Major interactions are generally avoided, moderate ones may need monitoring or a dose adjustment, and minor ones are usually low-risk. This page shows the documented mechanism and guidance. Label-documented interactions are not a complete safety review, so always confirm your own medications with a pharmacist or doctor. Educational information, not medical advice.
How They Interact
Terbinafine slows down the body's ability to break down tamsulosin by blocking a specific liver enzyme. This can lead to higher levels of tamsulosin in your blood.
What To Do
Use this combination with caution. Your doctor may need to adjust your dose, especially if you are taking more than 0.4 mg of tamsulosin.
FDA Label Information
Tamsulosin hydrochloride capsules should be used with caution in combination with moderate inhibitors of CYP3A4 (e.g., erythromycin), in combination with strong (e.g., paroxetine) or moderate (e.g., terbinafine) inhibitors of CYP2D6, or in patients known to be CYP2D6 poor metabolizers, particularly at a dose higher than 0.4 mg (e.g., 0.8 mg). The effects of concomitant administration of a moderate CYP2D6 inhibitor (e.g., terbinafine) on the pharmacokinetics of tamsulosin hydrochloride have not been evaluated [see Warnings and Precautions (5.2) and Clinical Pharmacology (12.3)].
Terbinafine Also Interacts With
- Ketoconazole minor
- Fluconazole minor
- Cyclosporine minor
- Trimethoprim minor
- Rifampin minor
Tamsulosin Also Interacts With
- Furosemide major
- Paroxetine moderate
- Warfarin moderate
- Erythromycin moderate
- Dutasteride moderate
Frequently Asked Questions
Can I take Terbinafine and Tamsulosin together?
This is a moderate interaction. Use this combination with caution. Your doctor may need to adjust your dose, especially if you are taking more than 0.4 mg of tamsulosin.
How serious is the interaction between Terbinafine and Tamsulosin?
This interaction is classified as "moderate" severity by the FDA. Moderate interactions may worsen your condition or change how your medications work.
Why do Terbinafine and Tamsulosin interact?
Terbinafine slows down the body's ability to break down tamsulosin by blocking a specific liver enzyme. This can lead to higher levels of tamsulosin in your blood.
Understanding the Terbinafine and Tamsulosin Interaction
FDA-approved prescribing information for these two drugs flags their combination as a moderate-severity interaction. Terbinafine belongs to the Allylamine Antifungal class and Tamsulosin belongs to the Alpha-1 Adrenergic Blocker class - two categories that can collide when co-prescribed. The mechanism described in FDA labeling is: Terbinafine slows down the body's ability to break down tamsulosin by blocking a specific liver enzyme. Severity tiers matter: major flags generally advise avoidance, moderate flags often require monitoring or dose adjustment, and minor flags may only call for awareness.
Context around a specific patient determines real-world impact. Terbinafine has 17 total documented interactions on file in this dataset, and Tamsulosin has 18. Each additional medication compounds the interaction surface, which is why pharmacists run full-profile checks rather than evaluating one pair at a time. FDA-derived guidance for this pair is: Use this combination with caution. Timing of doses, renal and hepatic function, age, and other concurrent prescriptions all shape whether a labeled interaction matters clinically.
An interaction flag is not a verdict. A large share of labeled interactions are managed routinely in clinical practice, the fix may be as simple as spacing doses or adding a monitoring test. Others require the prescriber to choose a different medication entirely. This page surfaces FDA-sourced labeling and openFDA data for educational purposes only; it is not medical advice and cannot account for your full clinical picture. Never start, stop, or adjust either Terbinafine or Tamsulosin based on a web page, speak with your prescriber or pharmacist before making any change.
Sources: FDA Drug Labels (SPL) via openFDA (2026). This is for informational purposes only and is not medical advice. Always consult your healthcare provider about drug interactions.
Read our methodology - how this data is sourced, computed, and verified.