A nomogram for prediction of absorption rate coefficient.

Background: Previous studies have suggested that nomogram can simplize complicated calculations of several variables. A simple nomogram was constructed to estimate absorption rate coefficient (k(a)) by using the peak time (tpeak) and the elimination rate coefficient (k(e)) of drugs administered orally.

Methods: The nomogram was based on the plasma concentration-time (C-T) curve equation and the function relation between t(peak), k(a) and k(e). A mathematical analysis was presented for the construction of single chart nomogram. To check the degree of accuracy of the developed nomogram, we used it to analyze retrospective profiles of 46 drugs and compared the ka values obtained graphically and those calculated by numerically solving the descriptive equation. In addition, we measured the carbocisteine concentration of 18 healthy volunteers by HPLC with fluorescence detection. To analyze performance error, the measured carbocisteine concentrations were compared with predicted concentrations by the ka obtained from the nomograms along with the other pharmacokinetic parameters.

Results: The estimated of k(a) values from nomograms were in very close proximity with the numerical values. The performance error was as follows: median performance error (MDPE) and median absolute performance error (MDAPE) were 1.32% and 18.15%, respectively.

Conclusions: The developed nomogram is accurate and reliable. The size of performance error meets the demand of clinical pharmacokinetics. Therefore, the nomograms can offer another convenient and easy method for rational individualized dosage regimens.