Abstract
In the first in this series of reporte 1), we reported the effects of cysteine compounds on the minimum inhibitory concentrations (MIC) of antibiotics in vitro to indicate the interaction between cysteine compounds and antibiotics.
In this report, we investigated L-methylcysteine hydrochloride (mecysteine, Pectite®). Among the antibiotics, i. e. sodium cephalothin (CET), cephalexin (CEX) and lincomycin hydrochloride (LCM), which had their potencies lowered by a concentration of 25mcg/ml of mecysteine, which is considered to approximate the concentration in the blood at clinical doses, in the first report, CEX and LCM administered per os were selected. Ampicillin (ABPC) which was reported to have its potency lowered by cysteine by RYUGE et al. 2, 3) and SATAKE et al.4, 5) was also selected and the interaction was investigated using the serum concentration of the antibiotics in humans as an index.
The subjects were 15 volunteers divided into three groups: the ABPC, CEX and LCM groups (5 persons each). The administration the same method, for all groups, started with administration of the antibiotic alone, followed by concomitant administration of the antibiotic and 100mg of mecysteine one week later.
The results showed that the serum concentrations due to a single oral administration simultaneously of 100mg of mecysteine and 250mg of ABPC, 250mg of CEX or 500mg of LCM were the same as the respective serum concentrations of ABPC, CEX and LCM administered alone, and there were no significant differences.
