- Enter the patient's age, weight (kg), sex, and serum creatinine (mg/dL). The Cockcroft–Gault creatinine clearance (CrCl) is computed automatically.
- Select an antibiotic from the list. The usual renally-adjusted adult dose for the patient's CrCl band appears, colour-coded green (standard), amber (reduced), or red (avoid / contraindicated / use alternative tool).
- These are usual-indication, normal-severity adult doses. Meningitis, endocarditis, and other deep-seated or severe infections require higher doses; HD/CRRT regimens differ and supplemental post-dialysis dosing may be needed.
- Always verify against the current drug label, the Sanford Guide, and your pharmacy before prescribing. If a drug you need is not listed, that is deliberate — only verified entries are included.
All computation runs in your browser; no values are stored or transmitted.
When to Use
Use this lookup when prescribing a predominantly renally-cleared antibiotic to an adult with reduced kidney function (acute kidney injury or chronic kidney disease) and you need a quick, sourced starting point for the renally-adjusted dose. The conventional metric for renal drug dosing is the Cockcroft–Gault creatinine clearance, which most drug labels and the Sanford Guide use to define their dose bands — so this tool computes CrCl from age, weight, sex, and serum creatinine and maps it to each drug's published bands.
Appropriate use
Adults with stable renal function in whom a covered antibiotic is being dosed for a usual-severity, normal-indication infection. The tool flags drugs to avoid at low CrCl (e.g., nitrofurantoin), drugs to reduce (most β-lactams, fluoroquinolones, TMP-SMX, fluconazole, IV acyclovir), and anchors that need no renal adjustment (ceftriaxone, azithromycin) for contrast.
When NOT to rely on it
These are usual-indication, normal-severity doses only. They do not apply to meningitis, endocarditis, febrile neutropenia, osteomyelitis, or other deep-seated/severe infections, which need higher doses. They do not give full hemodialysis, peritoneal dialysis, or CRRT regimens (supplemental post-HD dosing and continuous-therapy clearances differ). In unstable AKI, a steady-state CrCl from a single creatinine overestimates true clearance — consider kinetic GFR estimates and reassess frequently. Vancomycin and aminoglycosides are intentionally not dosed here — use the dedicated tools.
Pearls & Pitfalls
Reduce the dose, but keep killing the bug
For time-dependent agents (β-lactams, carbapenems), labels usually extend the interval rather than slash the milligram dose, preserving the peak needed for bactericidal activity. For concentration-dependent agents (fluoroquinolones, aminoglycosides), the goal is an adequate peak, so interval extension is again preferred over deep dose cuts. Don't under-dose a serious infection just because the kidney is impaired — adjust thoughtfully and give a full loading dose where appropriate (e.g., ceftazidime, levofloxacin, fluconazole).
Dose for the indication and the dialysis schedule
Severity and site change everything: meningitis, endocarditis, and febrile neutropenia use higher doses than the usual-indication figures shown here. On hemodialysis, several drugs (e.g., piperacillin-tazobactam, fluconazole) should be given after the session or with a supplemental post-HD dose. Always confirm the HD/CRRT regimen with pharmacy.
Pitfalls
(1) AKI is a moving target — a CrCl computed from one steady-state creatinine overestimates clearance when function is falling; reassess daily and consider kinetic estimates. (2) Nitrofurantoin is ineffective and risky below CrCl ~30 mL/min (Beers criteria) — avoid. (3) Avoid neurotoxic accumulation: cefepime, ceftazidime, and high-dose β-lactams cause encephalopathy/seizures when unadjusted in renal failure. (4) Weight matters: Cockcroft–Gault uses actual body weight here; in obesity an adjusted weight may be more appropriate and can change the band. (5) Garbage in, garbage out — a spurious creatinine or wrong weight invalidates the result.
Why Use It
Renally-cleared antibiotics accumulate when kidney function falls, and the consequences are real: cefepime and ceftazidime cause encephalopathy and seizures; fluoroquinolones and TMP-SMX add toxicity; nitrofurantoin loses efficacy and risks pulmonary and neurologic harm. Conversely, reflexive over-reduction can leave a serious infection underdosed. Matching the dose to the patient's creatinine clearance — the metric on which the drug labels and the Sanford Guide base their recommendations — is therefore a core safety step. This tool puts the Cockcroft–Gault calculation and a curated, sourced set of dose bands in one place so the adjustment can be made quickly and checked against an auditable reference, rather than from memory. It is an educational reference, not a prescribing authority: verify every dose against the current label and your pharmacy.
Renal Antibiotic Dosing — Dose Adjustment by CrCl
Enter the patient's age, weight, sex, and serum creatinine to compute the Cockcroft–Gault creatinine clearance, then select an antibiotic to see the usual renally-adjusted adult dose for that CrCl band. Doses are usual-indication, normal-severity adult guidance — meningitis, endocarditis, and dialysis differ.
⚕ Usual-indication, normal-severity adult renal-adjustment guidance only, computed from the Cockcroft–Gault CrCl. Verified against the FDA drug prescribing information, the Sanford Guide, and the Matzke/KDIGO drug-dosing report (see References). Meningitis, endocarditis, febrile neutropenia, and other severe/deep-seated infections require higher doses; hemodialysis, peritoneal dialysis, and CRRT regimens differ and may need supplemental dosing. AKI is dynamic — reassess as function changes. For licensed clinicians; always verify against the current label and your pharmacy before prescribing.
Next Steps
Use the computed CrCl and the drug's status flag to finalise the regimen and the monitoring plan.
- Standard (green): no renal adjustment needed at this CrCl — confirm the dose matches the indication's severity (escalate for meningitis, endocarditis, neutropenia).
- Reduced (amber): give the displayed renally-adjusted dose. Where a loading dose is indicated (ceftazidime, levofloxacin, fluconazole), give the full load first, then the adjusted maintenance dose. Recheck renal function and reassess as the patient stabilises.
- Avoid / contraindicated (red): choose an alternative agent (e.g., nitrofurantoin below CrCl 30) or, for vancomycin and aminoglycosides, switch to the dedicated calculators: Vancomycin AUC/MIC and Aminoglycoside dosing.
- Confirm the CrCl input independently with the Cockcroft–Gault calculator, and in AKI re-estimate clearance frequently.
- Verify every dose against the current drug label, the Sanford Guide, and your clinical pharmacist before prescribing.
Evidence & References
Cockcroft–Gault creatinine clearance
| Quantity | Formula |
|---|---|
| CrCl (mL/min) | [(140 − age) × weightkg] ÷ (72 × Scr) × 0.85 if female |
Dose bands implemented (usual indication, normal severity)
The values below are the auditable bands used by the calculator's JavaScript lookup. They are usual-adult renal-adjustment doses; severe/deep-seated infections and dialysis differ. Verify against the current label and Sanford Guide before prescribing.
| Drug | Normal (CrCl >50) | Moderate | Severe | End-stage / HD |
|---|---|---|---|---|
| Piperacillin-tazobactam | 3.375 g q6h | 2.25 g q6h (CrCl 20–40) | 2.25 g q8h (<20) | 2.25 g q8h + 0.75 g post-HD |
| Cefepime | 2 g q8h | 2 g q12h (30–60) | 2 g q24h (11–29) | 1 g q24h (<11 / HD, post-dialysis) |
| Ceftazidime | 1–2 g q8h | 1 g q12h (31–50) | 1 g q24h (16–30); 500 mg q24h (6–15) | 500 mg q48h (<6 / HD, post-dialysis) |
| Meropenem | 1 g q8h | 1 g q12h (26–50) | 500 mg q12h (10–25) | 500 mg q24h (<10) |
| Amoxicillin-clavulanate | 500–875 mg q12h | 250–500 mg q12h (10–30) | 250–500 mg q24h (<10) | 250–500 mg q24h + post-HD dose |
| Amoxicillin | 500 mg q8h / 875 mg q12h | 500 mg q12h (10–30) | 500 mg q24h (<10) | 500 mg q24h + post-HD dose |
| Ciprofloxacin | 400 mg IV q12h / 500–750 mg PO q12h | same (30–50) | 400 mg IV q24h / 500 mg PO q18–24h (<30) | 250–500 mg PO q24h after HD |
| Levofloxacin (750 mg) | 750 mg q24h | 750 mg q48h (20–49) | 750 mg ×1 then 500 mg q48h (<20) | 750 mg ×1 then 500 mg q48h |
| TMP-SMX | Usual dose | 50% of dose (CrCl 15–30) | Not recommended (<15) | Not recommended; dose post-HD if used |
| Nitrofurantoin | 100 mg q12h (CrCl ≥30) | — | Contraindicated (<30) | Contraindicated |
| Fluconazole | Full dose | 50% of maintenance after full load (CrCl ≤50) | 50% of maintenance (≤50) | Full dose after each HD session |
| Acyclovir (IV, 10 mg/kg) | 10 mg/kg q8h | 10 mg/kg q12h (25–50) | 10 mg/kg q24h (10–25) | 5 mg/kg q24h (<10), dose after HD |
| Ceftriaxone | No renal adjustment (max 2 g/day if combined severe hepatic + renal impairment) | |||
| Azithromycin | No renal adjustment | |||
References
- Gilbert DN, Chambers HF, Saag MS, et al. The Sanford Guide to Antimicrobial Therapy (current edition). Antimicrobial Therapy, Inc. — renal dose-adjustment tables.
- U.S. Food & Drug Administration. Prescribing information (package inserts) for piperacillin-tazobactam, cefepime, ceftazidime, meropenem, amoxicillin-clavulanate, ciprofloxacin, levofloxacin, sulfamethoxazole-trimethoprim, nitrofurantoin, fluconazole, acyclovir, ceftriaxone, and azithromycin. DailyMed / accessdata.fda.gov.
- Matzke GR, Aronoff GR, Atkinson AJ Jr, et al. Drug dosing consideration in patients with acute and chronic kidney disease — a clinical update from Kidney Disease: Improving Global Outcomes (KDIGO). Kidney Int. 2011;80(11):1122–1137. doi:10.1038/ki.2011.322.
