Effect of probenecid on serum rifampicin levels

Serum Rifampicin levels were determined by a microbiological assay using Staphylococcus aureus in 22 cases of leprosy after administering the drug with and without probenecid. Most of the patients showed higher serum rifampicin levels when probenecid was given along with rifampicin. Six patients showed statistically significant increase in the serum levels of the drug when given in the dose of 300 mg along with 1 g of probenecid one hour before breakfast and these levels were comparable with those obtained following administration of 450 mg of rifampicin alone two hours after breakfast. Thus administration of probenecid preceding rifampicin may be employed to reduce cost of drug as well as hepatotoxicity in patients requiring rifampicin for long duration.