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Cornell Pediatrics

Time to Target Level

Calculate the time it would take to achieve a target level from two plasma levels separated by a time interval.

Input Peak concentration mcg/mL
Input Trough concentration mcg/mL
Input Time to peak * hrs
Input Time to trough * hrs
Input Target level mcg/mL
time to target = 

* The "time to peak", "time to trough", and "time to target" are measured relative to the initiation of the dose.

Note: 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. At the very least, the "peak" should be obtained after the drug has had time to be fully distributed in the body.

The time interval entered is not the same as the dosing interval; it is the time between the two levels.

The formulas used are:

kelim = ln(Cpeak) - ln(Ctrough)

t = 0.693 / kelim


Created: October 18, 2013
Revised: October 19, 2013.

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