Neonatal prescribing is unforgiving: small weights, rapidly changing physiology, and narrow margins mean an arithmetic slip can be dangerous. This calculator gives a fast weight-based single dose for common NICU drugs, alongside the usual route and an interval guide, as a cross-check against the chart.
How it works
Almost all neonatal dosing is expressed per kilogram of body weight. The calculator applies the simple relationship:
single dose = dose per kg x weight (kg)Each drug in the list carries its representative per-kilogram dose, its route, and an interval guide. For aminoglycosides and glycopeptides the interval widens in the most premature infants because clearance is slower, and the guide reflects that pattern.
Drugs included and their dosing context
The reference covers the drugs most commonly encountered in NICU practice, including:
- Gentamicin — once-daily or extended-interval dosing; serum levels are essential to guide repeat dosing.
- Vancomycin — intervals lengthen significantly in extreme prematurity; trough or AUC monitoring required.
- Caffeine citrate — a loading dose followed by maintenance; well tolerated with a wide safety margin.
- Morphine — weight-based IV bolus or infusion; continuous respiratory monitoring is mandatory.
- Surfactant — dosed in mL/kg via intratracheal route; local protocol governs repeat doses and timing.
- Indomethacin — PDA closure, given as a three-dose course, weight-based.
- Adrenaline / epinephrine — resuscitation and bradycardia doses, shown with approximate volumes.
Worked examples
A gentamicin dose of 5 mg/kg in a 1.5 kg infant gives a single dose of 7.5 mg. A caffeine citrate loading dose of 20 mg/kg in a 900 g (0.9 kg) infant gives 18 mg. In both cases, the arithmetic is straightforward — the danger lies in transposing decimal points or confusing kilograms with grams, which is why a cross-check tool adds value even for experienced prescribers.
Why interval is as important as dose
In neonates — especially those born before 32 weeks’ gestation — drug elimination is driven by immature renal and hepatic function that matures rapidly over the first weeks of life. The same weight-based dose given too frequently accumulates to toxic levels; given too infrequently it provides inadequate therapeutic cover. The interval guide in this tool reflects the direction of that effect (longer intervals in smaller, more premature infants), but local formularies and therapeutic drug monitoring results always govern actual prescribing.
Notes and limitations
The figures are educational and assume standard organ function. They do not replace therapeutic drug monitoring: gentamicin and vancomycin dosing in particular must be steered by measured levels, and intervals adjusted by postmenstrual age. Surfactant, adrenaline, and resuscitation drugs are included with their volume equivalents, but local protocols govern repeat dosing. Always confirm every dose against your unit’s neonatal formulary and the individual baby before administration.