Why probenecid given with penicillin in treating syphilis ? what is the role of the probencid in the treating syphilis ?

Helping PCM: Probenecid is used to increase the efficacy of penicillin, prolong its action.

Use of probenecid: Probenecid inhibits the tubular secretion of penicillin and elevates penicillin plasma levels by any route the antibiotic is given. A 2-fold to 4-fold elevation has been demonstrated for various penicillins. That is why probenecid is given with penicillin.

Delay excretion: Probenecid is not itself an antibiotic. It is often given together with penicillin in infections treatable with penicillin in order to delay the excretion of the penicillin and allow lower doses to be given (or equivalent doses to achieve higher blood levels). However, it is rarely used in the present day, at least in high-resource areas.