Summary of Useful Formulae and Definitions

Drug concentrationC = C0 e−ktC = drug concentration at time t after C0
C0 = drug concentration at reference time
k = elimination rate constant
t = time between C and C0
Elimination rate constantk = ln2/T0.5k = elimination rate constant
ln2 = 0.693
T0.5 = half clearance time
Volume of distributionV = amount in body (μg)/actual C0V = volume of distribution
Actual C0 = concentration at time of administration
Area under curveAUC0–∞ = FD/VkAUC0–∞ = area under curve (total drug dose) from time 0 to infinity
F = fraction of drug absorbed
D = dose
V = volume of distribution
k = elimination rate constant
ClearanceCL = k × VCL = clearance
k = elimination rate constant
V = volume of distribution
Time to maximum concentrationTmax = (1/[ka − k]) ln (ka/k)Tmax = time to maximum concentration
ka = absorption rate constant
k = elimination rate constant