The plasma or blood concentration profiles are fitted by single or two compartment open models using log-linear regression analyses. For two compartment models, "feathering" is performed at 95% equilibration time obtained from raw pharmacokinetic data. The equations have been programmed onto a Texas Instrument SR 52 pocket calculator and recorded on 8.5 X 1.7 cm magnetic strips, facilitating drug dosage regimen calculations through individual patient titrations in a clinical setting.