Why does trimethoprim raise serum creatinine without decreasing GFR?

Trimethoprim inhibits renal tubular secretion of creatinine via OCT2 transporters, raising measured serum creatinine by 0.1–0.3 mg/dL without changing true GFR. This is a drug effect, not renal toxicity, and reverses on discontinuation.

What TMP-SMX dose adjustment is recommended for CrCl <30 mL/min?

At CrCl 15-30 mL/min: half the standard dose; at CrCl <15 mL/min: avoid if possible or use with extreme caution with K+ monitoring given hyperkalemia risk. Pneumocystis prophylaxis: alternative to TMP-SMX when severely impaired.

Trimethoprim Renal Dose Adjustment Calculator

Calculate trimethoprim (TMP and TMP-SMX) dose adjustment for renal impairment, noting that trimethoprim competitively inhibits tubular creatinine secretion, causing apparent creatinine rises without true GFR change.

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Trimethoprim Renal Dose Adjustment Calculator

Frequently Asked Questions

Why does trimethoprim raise serum creatinine without decreasing GFR?

What TMP-SMX dose adjustment is recommended for CrCl <30 mL/min?