- Enter the patient's age, weight (kg), sex, and serum creatinine (mg/dL). The Cockcroft–Gault creatinine clearance (CrCl) is computed automatically.
- Select a medicine from the list. The usual renally-adjusted adult dose or dosing strategy for the patient's CrCl band appears, colour-coded green (standard), amber (reduced/caution), or red (avoid / contraindicated / needs specialist judgment).
- These are usual-indication, normal-severity adult doses. Allopurinol is shown as a starting-dose and titration strategy, not a fixed dose cap — see the Pearls section for why.
- Always verify against the current drug label 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 gabapentin, pregabalin, allopurinol, tramadol, or colchicine to an adult with reduced kidney function (acute kidney injury or chronic kidney disease) and you need a quick, sourced starting point. Gabapentin and pregabalin leave the body almost entirely through the kidney, so their bands are conventional CrCl dose tables. Allopurinol is different — modern guidance titrates to a target uric acid rather than capping the dose by renal function — so its result is a starting-dose and monitoring strategy, not a single number. Tramadol and colchicine both need caution flags beyond a simple dose cut.
Appropriate use
Adults with stable renal function starting or continuing one of these five medicines. The tool flags drugs that need a straightforward CrCl-banded dose cut (gabapentin, pregabalin), a starting-dose-and-titrate strategy (allopurinol), and drugs where the renal caution is really about accumulation risk and drug interactions (tramadol, colchicine).
When NOT to rely on it
These are usual-adult guidance only. 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. This tool does not check for drug-drug interactions beyond the colchicine CYP3A4/P-glycoprotein warning built into its result — always reconcile the patient's full medicine list separately.
Pearls & Pitfalls
Allopurinol: start low, treat to target — don't just cap the dose
The older Hande nomogram capped allopurinol's maintenance dose by creatinine clearance alone (e.g., 100 mg/day at CrCl 30–59). The 2020 American College of Rheumatology gout guideline moved away from that: start at ≤100 mg/day (lower still in CKD stage ≥3), then titrate the dose upward every 2–5 weeks guided by serial serum urate measurements, targeting urate <6 mg/dL — regardless of renal function. A patient with reduced eGFR is not capped at a low dose forever; they are simply titrated more cautiously.
Gabapentinoid accumulation looks like something else
Gabapentin and pregabalin are renally cleared almost unchanged. In reduced kidney function, an unadjusted dose accumulates and can present as drowsiness, confusion, ataxia, or myoclonus — easy to misattribute to age, uremia itself, or another sedating medicine rather than the drug that is actually the cause. When an older CKD patient becomes unexpectedly somnolent or confused, check whether a gabapentinoid dose was ever adjusted for their current renal function.
Pitfalls
(1) Colchicine + a CYP3A4/P-glycoprotein inhibitor (clarithromycin, cyclosporine, ketoconazole) in a patient with reduced kidney function is a recognized cause of fatal colchicine toxicity — the combination, not renal impairment alone, is the danger. (2) AKI is a moving target — a CrCl from one steady-state creatinine overestimates clearance when function is falling; reassess and consider kinetic estimates. (3) Tramadol's extended-release formulation is generally avoided at CrCl <30 — the immediate-release form with an extended interval is the safer path. (4) Weight matters: Cockcroft–Gault uses actual body weight here; in obesity an adjusted weight may be more appropriate. (5) Garbage in, garbage out — a spurious creatinine or wrong weight invalidates the result.
Why Use It
These five medicines are common, frequently prescribed alongside each other for pain and gout in CKD patients, and each fails differently when kidney function is not accounted for: gabapentinoids accumulate into sedation and falls, allopurinol under-titrated leaves gout under-treated while over-capped-by-old-rules under-treats it further, and colchicine combined with an interacting drug in renal impairment has caused fatalities. Matching the strategy to the patient's creatinine clearance — and to current guideline thinking, not just an outdated nomogram — is a core safety step. This tool puts the Cockcroft–Gault calculation and a curated, sourced set of dose bands in one place. It is an educational reference, not a prescribing authority: verify every dose against the current label and your pharmacy.
Renal Dosing: Nerve Pain & Gout Medicines — Dose Adjustment by CrCl
Enter the patient's age, weight, sex, and serum creatinine to compute the Cockcroft–Gault creatinine clearance, then select a medicine to see the usual renally-adjusted adult dose or dosing strategy for that CrCl band. Allopurinol shows a starting-dose and titration strategy rather than a fixed cap.
⚕ Usual-adult renal-dosing guidance only, computed from the Cockcroft–Gault CrCl. Gabapentin/pregabalin/tramadol bands verified against FDA prescribing information; allopurinol reflects the 2020 ACR gout guideline's start-low/titrate-to-target strategy, not a fixed dose cap; colchicine carries a mandatory drug-interaction caution (see References). 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): usual adult dose at this CrCl — no renal adjustment needed.
- Reduced (amber): give the displayed renally-adjusted dose or starting-dose/titration strategy. For allopurinol, this means starting low and titrating to a serum urate target, not stopping at a fixed dose. Recheck renal function and reassess as the patient's status changes.
- Caution (amber/red) — colchicine: before prescribing, check the patient's full medicine list for CYP3A4 or P-glycoprotein inhibitors (clarithromycin, cyclosporine, ketoconazole, ritonavir). The combination with reduced renal function is a recognized cause of fatal toxicity — reduce the dose further or avoid the combination.
- Avoid (red): choose an alternative agent or defer to specialist judgment at this CrCl.
- Confirm the CrCl input independently with the Cockcroft–Gault calculator, and in AKI re-estimate clearance frequently.
- For antibiotics, DOACs, or metformin, use the dedicated calculators: Renal antibiotic dosing, DOAC renal dosing, and Metformin safety checker.
- Verify every dose against the current drug label 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
The values below are the auditable bands used by the calculator's JavaScript lookup. Verify against the current label before prescribing.
| Drug | CrCl ≥60 | CrCl 30–59 | CrCl 15–29 | CrCl <15 / HD |
|---|---|---|---|---|
| Gabapentin | 900–3600 mg/day (3 divided doses) | 400–1400 mg/day (2 divided doses) | 200–700 mg/day (single daily dose) | 100–300 mg/day; 125–350 mg supplemental dose after each 4-hr HD session |
| Pregabalin | 150–600 mg/day (2–3 divided doses) | 75–300 mg/day (2–3 divided doses) | 25–150 mg/day (1–2 divided doses) | 25–75 mg/day once daily; 25–100 mg supplemental dose after each HD session |
| Allopurinol | Start ≤100 mg/day (≤50 mg/day if CKD stage ≥3, i.e. roughly CrCl <60), titrate every 2–5 weeks guided by serum urate, target <6 mg/dL — not a fixed dose cap by CrCl. Consider HLA-B*5801 testing before starting in patients of Han Chinese, Thai, or other high-risk ancestry. | |||
| Tramadol (IR) | 50–100 mg q4–6h, max 400 mg/day | same as CrCl ≥60 | 50–100 mg q12h, max 200 mg/day; avoid extended-release | 50–100 mg q12h, max 200 mg/day; avoid extended-release; significantly dialyzable |
| Colchicine (acute flare) | 1.2 mg at onset, then 0.6 mg 1 hr later (1.8 mg total); do not repeat within 14 days | same as CrCl ≥60, monitor closely | 1.2 mg single dose only (omit the follow-up 0.6 mg dose); do not repeat within 14 days | Use with substantial caution and specialist input; avoid routine chronic prophylactic dosing |
Colchicine drug-interaction warning
Strong CYP3A4 or P-glycoprotein inhibitors — clarithromycin, cyclosporine, ketoconazole, ritonavir — raise colchicine levels; combined with reduced kidney function, this has caused fatal toxicity (Finkelstein et al., 2010). Reconcile the patient's full medicine list before prescribing colchicine at any renal function.
References
- U.S. Food & Drug Administration. Prescribing information (package inserts) for gabapentin, pregabalin, and tramadol. DailyMed / accessdata.fda.gov.
- FitzGerald, J. D., Dalbeth, N., Mikuls, T., et al. (2020). 2020 American College of Rheumatology guideline for the management of gout. Arthritis & Rheumatology, 72(6), 879–895. https://doi.org/10.1002/art.41247
- Finkelstein, Y., Aks, S. E., Hutson, J. R., Juurlink, D. N., Nguyen, P., Dubnov-Raz, G., Pollak, U., Koren, G., & Bentur, Y. (2010). Colchicine poisoning: The dark side of an ancient drug. Clinical Toxicology, 48(5), 407–414. https://doi.org/10.3109/15563650.2010.495348
