What body weight is used for aminoglycoside dosing?

For underweight patients (ABW 1.2 × IBW), adjusted body weight (AdjBW = IBW + 0.4 × [ABW − IBW]) is used. This calculator auto-selects the appropriate weight and displays which one was used.

What is extended-interval dosing?

Extended-interval (or once-daily) aminoglycoside dosing gives a larger single dose — typically 5–7 mg/kg for gentamicin/tobramycin or 15 mg/kg for amikacin — once every 24, 36, or 48 hours depending on renal function. This exploits the concentration-dependent killing and post-antibiotic effect of aminoglycosides while minimizing nephrotoxicity during the drug-free trough period.

How is creatinine clearance estimated?

CrCl is estimated with the Cockcroft-Gault equation: CrCl = [(140 − age) × selected weight × (0.85 if female)] / (72 × SCr). This implementation uses the selected dosing weight (ABW if underweight, IBW if normal weight, or AdjBW if ABW > 1.2 × IBW). It applies an SCr floor of 0.6 mg/dL. Weight selection and low-SCr handling vary by protocol, so clinicians must verify both locally.

Why are aminoglycosides dosed differently from other antibiotics?

Aminoglycosides exhibit concentration-dependent bactericidal activity and a prolonged post-antibiotic effect. Higher peak concentrations relative to the MIC improve killing. Nephrotoxicity is linked to sustained drug levels in renal tubular cells, so a drug-free interval (low trough) reduces toxicity. These properties favor large infrequent doses over small frequent ones.

When should extended-interval dosing NOT be used?

Extended-interval dosing is generally avoided in pregnancy, burns covering > 20% BSA, ascites, endocarditis (especially enterococcal synergy dosing), and severe or unstable renal dysfunction. Some institutional protocols also exclude morbid obesity. Traditional dosing with pharmacokinetic monitoring may be preferred in these populations; always verify local eligibility criteria.

Is this calculator a replacement for therapeutic drug monitoring?

No. Aminoglycosides require serum level monitoring (peaks and troughs or Hartford 6–14 h levels) to individualize therapy. This tool provides initial dose estimates only. Dosing must be adjusted based on measured levels and clinical response by a licensed pharmacist or physician.

Aminoglycoside Dosing Calculator

Calculate weight-based initial doses and extended-interval (Hartford nomogram) dosing for gentamicin, tobramycin, and amikacin based on patient weight and renal function.

Patient Parameters

Age (years)

Sex

Height (cm)

Actual Weight (kg)

Serum Creatinine (mg/dL)

Aminoglycoside

Educational reference only. All dosing results, weight selection, renal-function assumptions, and extended-interval eligibility must be verified against the local protocol by a licensed pharmacist or physician. This tool does not replace clinical judgment or therapeutic drug monitoring.

Enter patient data and click Calculate Dose

Summary

Calculate weight-based initial doses and extended-interval (Hartford nomogram) dosing for gentamicin, tobramycin, and amikacin based on patient weight and renal function.

How it works

Enter patient age, sex, actual body weight, and serum creatinine.
Select the aminoglycoside: gentamicin, tobramycin, or amikacin.
The tool calculates creatinine clearance using Cockcroft-Gault and the displayed dosing-weight policy.
Traditional dosing is shown: standard mg/kg dose divided into q8h, q12h, or q24h intervals adjusted for CrCl.
Extended-interval dosing is calculated using the Hartford nomogram target dose (7 mg/kg for gentamicin/tobramycin; 15 mg/kg for amikacin) with interval selected by CrCl.
Results display the calculated dose per interval, total daily dose, and the estimated dosing interval.

Use cases

Calculate an initial gentamicin dose for gram-negative bacteremia.
Determine tobramycin dosing for a patient with mild renal impairment.
Apply Hartford nomogram extended-interval amikacin for serious infections.
Estimate CrCl before selecting aminoglycoside dosing interval.
Support pharmacy students learning aminoglycoside pharmacokinetics.
Cross-check a clinical dose recommendation during rounds.
Compare traditional versus extended-interval strategies side by side.
Screen for dose adjustments needed in elderly or renally impaired patients.

Frequently Asked Questions

Last updated: 2026-09-19 · Reviewed by Nham Vu

Aminoglycoside Dosing Calculator

Patient Parameters

Patient Pharmacokinetic Estimates

Traditional Weight-Based Dosing

Extended-Interval Dosing (Hartford Nomogram)

Summary

How it works

Use cases

Frequently Asked Questions

Aminoglycoside Dosing Calculator

Use the Aminoglycoside Dosing Calculator

Patient Parameters

Patient Pharmacokinetic Estimates

Traditional Weight-Based Dosing

Extended-Interval Dosing (Hartford Nomogram)

Summary

How it works

Use cases

Frequently Asked Questions