The gentamicin once-daily dosing calculator provides an extended-interval aminoglycoside starting dose and suggests a dosing interval based on renal function, following the Hartford-style nomogram used in antimicrobial stewardship.
How it works
The dose is simply the target per kilogram times the dosing weight:
Dose (mg) = target(mg/kg) × dosing weight(kg)Common targets are 5–7 mg/kg, with 7 mg/kg used for serious Gram-negative
sepsis. The result is usually rounded to a practical increment (for example to
the nearest 20 mg).
The interval is chosen from creatinine clearance using the Hartford nomogram bands:
- CrCl > 60 mL/min → every 24 hours.
- CrCl 40–60 mL/min → every 36 hours.
- CrCl 20–40 mL/min → every 48 hours.
- CrCl < 20 mL/min → avoid extended interval; use conventional dosing with levels.
A drug level drawn 6–14 hours after the dose is plotted on the nomogram to confirm or lengthen the interval.
Example and notes
A 70 kg patient with a CrCl of 75 mL/min dosed at 7 mg/kg receives
7 × 70 = 490 mg, rounded to about 480–500 mg, every 24 hours.
Extended-interval dosing is generally avoided in pregnancy, major burns, ascites, endocarditis, cystic fibrosis, and severe renal impairment, where conventional dosing with peak and trough monitoring is preferred. This tool gives only a starting dose and suggested interval — always confirm with therapeutic drug monitoring and follow local protocol.