Drug interactions
Sulfamethoxazole + Tolbutamide
Severity: Moderate
Sulfamethoxazole and Tolbutamide: 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
Sulfamethoxazole can increase the glucose-lowering effect of tolbutamide, and hypoglycemia has been reported with sulfonamide and sulfonylurea combinations. Patients with renal impairment or advanced age are at greater risk.
What this interaction means in plain words
Sulfamethoxazole and Tolbutamide 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
Sulfamethoxazole inhibits CYP2C9 metabolism of tolbutamide and may displace it from protein binding.
What to do
Check blood glucose frequently during and after the antibiotic course and reduce the tolbutamide dose if hypoglycemia occurs; consider an alternative antibiotic where feasible.
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 Sulfamethoxazole and Tolbutamide, 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 Tolbutamide
- Glyburide-metformin + Tolbutamide Major
- Insulin degludec-liraglutide + Tolbutamide Major
- Aceclofenac + Tolbutamide Moderate
- Acemetacin + Tolbutamide Moderate
- Acetylsalicylic acid + Tolbutamide Moderate
- Albiglutide + Tolbutamide Moderate
Frequently asked questions
Can I take Sulfamethoxazole with Tolbutamide?
MediHelp rates the interaction as moderate. Sulfamethoxazole and Tolbutamide 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. Sulfamethoxazole can increase the glucose-lowering effect of tolbutamide, and hypoglycemia has been reported with sulfonamide and sulfonylurea combinations. Patients with renal impairment or advanced age are at greater risk.
How serious is the interaction between Sulfamethoxazole and Tolbutamide?
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 blood glucose frequently during and after the antibiotic course and reduce the tolbutamide dose if hypoglycemia occurs; consider an alternative antibiotic where feasible.
What other medicines interact with Tolbutamide?
MediHelp also lists interactions of Tolbutamide with, for example, Glyburide-metformin, Insulin degludec-liraglutide, Aceclofenac. The full list is on the Tolbutamide 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.
