Use of a programmable calculator to determine steady-state levels of drugs eliminated by parallel first-order and Michaelis-Menten kinetics
Crow, J.W.; Levy, G.
American Journal of Hospital Pharmacy 35(9): 1075-1077
1978
ISSN/ISBN: 0002-9289 PMID: 696752 Document Number: 137061
A programmable calculator procedure for the determination of steady-state levels of drugs eliminated by one or more apparent first-order plus one or two Michaelis-Menten processes in parallel is described. The differential expression for this pharmacokinetic system was converted to a reduced cubic equation suitable for calculators with trigonometric functions. A detailed program description and user instructions are presented. Steady-state levels of salicylic acid as a function of dosing rate were calculated to illustrate use of the program in clinical pharmacokinetics. The calculator program provides a facile and rapid means of determining the effect of changes in dosing rate, bioavailability and elimination constants on steady-state levels of salicylic acid and certain other drugs with nonlinear elimination characteristics.