How it works — HLCalc

The model

HLCalc uses one compartment, first-order elimination and linear superposition of doses.

Elimination rate: ke = ln 2 / (t½ × multiplier)
Instant absorption: C(t) = F·D/Vd · e^(−ke·t)
First-order absorption: C(t) = F·D·ka / (Vd·(ka − ke)) · (e^(−ke·t) − e^(−ka·t))
Without a volume of distribution or body weight, the amount in body (mg) is shown instead of concentration.
Time to steady state is taken as 5 × t½.

Injectable esters

For depot injections the half-life in the library is an apparent, ester- and depot-limited value, not the hormone's own elimination half-life. Doses are entered as mg of the ester and converted to the active moiety. A single half-life cannot reproduce the delayed rise and slow tail of a real depot, so treat those curves as approximations.

Combining drugs

HLCalc never sums different drugs in mg or mg/L. The only exceptions are drugs that deliver the same active moiety, and the normalised "% of steady-state peak" mode.

Limits

This is a research and educational tool, not a medical device, and the bundled data is unverified. See the disclaimer on the HLCalc page.