Weibull function fits to pharmacokinetic data of ribavirin in man

Weibull function C = Bts-1exp(-lambda ts) was used to describe plasma concentration-time data of ribavirin in 6 healthy subjects following an i.v. dose of 600 mg. A good fit was found in each of the subjects, where the coefficients of determination r2 were > 0.99. The parameters estimated were as follows: B, 5.90 +/- 1.86 micrograms.h1-s; lambda, 0.607 +/- 0.156 h-s; and s, 0.339 +/- 0.085, respectively. The results were compared with those by triexponential function. By providing lower values of AIC and SD, as well as higher values of r2, the Weibull function proved to be superior to triexponential function for data of 3 subjects. These results indicated that both Weibull function and triexponential function provided a good fit of plasma concentration-time data of ribavirin in man following an i.v. dose.