Drug interactions
Cimetidine + Trimethoprim/Sulfamethoxazole
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.
Overview
Additive increases in serum creatinine without true GFR decline may occur due to inhibited tubular secretion of creatinine, potentially confounding assessment of renal function.
Mechanism of action
Pharmacokinetic/Pharmacodynamic: Both cimetidine and trimethoprim inhibit renal tubular secretion of creatinine (via OCT2/MATE transporters), causing a reversible rise in serum creatinine independent of GFR.
Clinical management
Obtain baseline renal function; expect a small, reversible rise in SCr within a few days. If changes would alter therapy, confirm kidney function with cystatin C or measured CrCl and assess for true AKI (urine output, BUN, clinical status).
Drug reference
References
- Bactrim (sulfamethoxazole and trimethoprim) Prescribing Information — FDA Label
- Tagamet HB (cimetidine) Prescribing Information — FDA Label
- Trimethoprim-sulfamethoxazole (TMP-SMX): Drug Information — UpToDate
Frequently asked questions
Can I take Cimetidine with Trimethoprim/Sulfamethoxazole?
The interaction is rated: Moderate. Additive increases in serum creatinine without true GFR decline may occur due to inhibited tubular secretion of creatinine, potentially confounding assessment of renal function.
How serious is the interaction between Cimetidine and Trimethoprim/Sulfamethoxazole?
The interaction is rated: Moderate. Evidence level: Moderate.
How is the interaction between Cimetidine and Trimethoprim/Sulfamethoxazole managed?
Obtain baseline renal function; expect a small, reversible rise in SCr within a few days. If changes would alter therapy, confirm kidney function with cystatin C or measured CrCl and assess for true AKI (urine output, BUN, clinical status).
Why do Cimetidine and Trimethoprim/Sulfamethoxazole interact?
Pharmacokinetic/Pharmacodynamic: Both cimetidine and trimethoprim inhibit renal tubular secretion of creatinine (via OCT2/MATE transporters), causing a reversible rise in serum creatinine independent of GFR.
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