Individualizing phenytoin dosage regimens using a programmable calculator.

A programmable calculator procedure for the determination of individualized phenytoin dosage regimens is described. The calculator is programmed based on a one-compartment, open model using the Michaelis-Menten equation. A detailed description of the programs and user instructions are presented. The programs allow calculation of oral dosage regimens and steady-state phenytoin levels. The first two programs require a given dose and one corresponding steady-state minimum concentration point to estimate a dosage regimen and steady-state serum level. The second two programs, which provide a more accurate prediction of dosage regimen and steady-state serum levels, require two dose and steady-state minimum concentration poits. The calculator programs provide a rapid and reliable means of estimating a patient's phenytoin dosage regimens and steady-state serum levels.