Drug interactions
Chlorpropamide + Sulfamethoxazole
Severity: Major
Chlorpropamide and Sulfamethoxazole: major interaction.
Last updated Sources: US FDA label
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 sulfonylureas and has been linked to serious hypoglycemia. The risk is higher in elderly patients and those with renal impairment.
What this interaction means in plain words
Chlorpropamide and Sulfamethoxazole can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Why it happens
Sulfamethoxazole inhibits CYP2C9 and displaces sulfonylureas from plasma proteins.
What to do
Monitor blood glucose frequently and reduce the chlorpropamide dose if needed. Consider an alternative antibiotic in high-risk patients.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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References
Other interactions of Chlorpropamide
Frequently asked questions
Can I take Chlorpropamide with Sulfamethoxazole?
MediHelp rates the interaction as major. Chlorpropamide and Sulfamethoxazole can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Sulfamethoxazole can increase the glucose-lowering effect of sulfonylureas and has been linked to serious hypoglycemia. The risk is higher in elderly patients and those with renal impairment.
How serious is the interaction between Chlorpropamide and Sulfamethoxazole?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor blood glucose frequently and reduce the chlorpropamide dose if needed. Consider an alternative antibiotic in high-risk patients.
What other medicines interact with Chlorpropamide?
MediHelp also lists interactions of Chlorpropamide with, for example, Ethanol, Exenatide, Insulin degludec-insulin aspart. The full list is on the Chlorpropamide page.
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