Effect of cysteine on oltipraz blood levels in green monkeys (Cercopithecus aethiops)

Oral coadministration of oltipraz, an antischistosomal compound, with cysteine to green monkeys (Cercopithecus aethiops) led to a marked increase in both the extent and rate of oltipraz bioavailability. The drug blood levels were monitored using a single extraction gas-liquid chromatographic assay. When 6 healthy adult animals were given oltipraz together with cysteine in a crossover study, peak serum concentrations, areas under the curve and absorption rate constants of oltipraz were on average 7 times greater than when the drug was administered alone. Oltipraz peak serum concentrations were reached 1 h earlier as a result of cysteine administration (2 h after dosing). At present, the mechanisms responsible for the effect(s) of cysteine on oltipraz bioavailability have not been identified. The marked increase in oltipraz bioavailability produced by coadministration of cysteine, irrespective of the exact mechanisms involved, may have significant clinical implications with regard to the treatment of schistosomiasis. Our results also indicate that oltipraz blood levels seem to be influenced by some sex-related factors. Male monkeys had higher oltipraz blood levels than females. These sex-induced differences were more evident in oltipraz-cysteine-treated monkeys.