Loading Dose Calculator
Calculate a loading dose and its matching maintenance dose from a drug's pharmacokinetic parameters.
This tool calculates both a loading dose and the maintenance dose that follows it, for drugs where getting to a therapeutic level quickly matters — it's built around a fixed list of drugs with known pharmacokinetic parameters, not a free-text formula you fill in yourself. See How Calculator Tools Work for the shared layout.
Inputs
- Drug — selected from the built-in list (each entry carries its volume of distribution, target concentration, half-life, bioavailability, and protein binding)
- Weight (kg)
- Dosing interval (hours — defaults to 8)
- CrCl (optional) — enables a renal-impairment warning if the drug requires renal adjustment
The formulas
Loading dose = (Vd × weight × target concentration) / bioavailability
Maintenance dose = Loading dose × (1 − e^(−ke × dosing interval))where ke (elimination rate constant) = 0.693 ÷ the drug's half-life. Time to steady state is estimated as roughly 4.5 half-lives.
Warnings you might see
- CrCl entered and below 60, and the drug requires renal adjustment: the maintenance dose may need reducing — check renal dosing guidelines before finalising.
- Drug requires hepatic adjustment: a reminder to check the patient's Child-Pugh class — see Hepatic Dose Adjustment.
This tool only covers the specific drugs in its built-in list — if the drug you need isn't in the selector, it isn't supported here yet, and a loading/maintenance dose should be calculated manually or sourced from another reference.