Plasma concentration-time data were used to calculate PK parameters for amifampridine and the 3-
N-acetyl metabolite using noncompartmental analysis (
Phoenix WinNonlin 6.1; Pharsight Corporation, Cary, NC). The values for
Cmax and
Tmax were obtained directly from plasma-time concentration data by inspection without interpolation. The values for AUC
0-t were calculated by the linear trapezoidal rule. The AUC
0-4h values for each multiple dosing interval in Part 2 were calculated using a 0–4 h reference time interval (not clock time) for each of the four doses on Days 1 and 3. The apparent
t½ was calculated by 0.693/
λz, where the terminal elimination rate constant
λz was determined by log-linear regression of the terminal plasma concentrations. The AUC
0-∞ was calculated by AUC
0-t + C
t/
λz, where C
t is the last measurable plasma concentration for measured drug or metabolite. The apparent oral clearance CL/
F was calculated by dose/AUC
0-∞, where
F represents the unknown fraction of absorbed drug. The apparent oral volume of distribution
Vdz/
F was calculated based on the terminal elimination rate constant by (CL/F) · 1/
λz. The apparent oral volume of distribution at steady state
Vdss/
F was calculated as MRT
0-∞ · CL/
F, where MRT
0-∞ is the mean residence time extrapolated from time 0 to infinity.
Haroldsen P.E., Garovoy M.R., Musson D.G., Zhou H., Tsuruda L., Hanson B, & O’Neill C.A. (2014). Genetic variation in aryl N-acetyltransferase results in significant differences in the pharmacokinetic and safety profiles of amifampridine (3,4-diaminopyridine) phosphate. Pharmacology Research & Perspectives, 3(1), e00099.