Calculate the half-life of a drug from two plasma levels separated by
a time interval.
Note:
The "peak" should be obtained after the drug has
been fully distributed, and the "trough" obtained
at some interval later. These levels need not be the "true"
peak or trough, as long as they are separated in time. The
longer the time interval between the levels, the better the
estimate.
If the levels are drawn around a dose (peak, dose, trough)
rather than after the same dose (dose, peak, trough),
the calculations here would be invalid if steady-state conditions
are not satisfied.
Also note that the time interval entered is not the same as the
dosing interval.
The formulae used are:
| kelim = |
(ln(Cpeak)
- ln(Ctrough) |
 |
| tinterval |
t½
= 0.693 / kelim
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