Abstract
The drug residue at the injected site after instramuscular administration of the water solution of sodium sufamonemethoxine (SMM, 10 mg/kg) was estimated by means of pharmacokinetic analysis of plasma concentration time data in 10 Goettingen miniature swine. With the pharmacokinetic analysis of the changes in plasma concetration of the drug following intramusculasr and intravenous injection, it was found that the drug was completely absorved from the injection site, i.e. F (bioavailability) was about 1. The overall absorption process obeyed a first order kinetics and the rate constant of absorption (ka) was calculated to be 2.87±2.14 (hr-1n=8) by Loo-Riegelman method. Acoordingly, the mean value of fraction-unab-sorbed at the injection site was expressed as following equation; 1-(1 -e-2.87t). The ratio of drug concentration at the non-injected muscle to that of plasma during the elimination phase was about 0.428±0.0331 (hr-1 n=6). Assuming 1 ml of the tissue at the injection site was the minimum distribution volume for 1 ml of the drug solution and employing the lower 95% confidential limit of ka value, a possible highest concentration of the drug at the injection site became identical to that in the non-injected musle 13.3 hr after the drug injection. On the other hand, an absorption ending time determined by the chemical assay of the muscle samples collected from serially slaughtered animals after intramuscular injection of the drug around 5hr. Accordingly, in the case of such a water soluble drug as SMM, the time of absorption ending after the intramuscular injection could be predicted by means pharmacokinetic analysis of plasma drug time concentration data conservatively.
