ALCOHOL REDUCE ITS EFFICACY. SALICYLATES INCLUDING ASPIRIN & PROBENECID ARE MUTUALLY ANTAGONISTIC AND SHOULD NOT BE GIVEN TOGATHER. IT ENHANCES EFFECTS OF ORAL ANTIDIABETICS, INDOMETHACIN, AMINOSALICYLIC ACID, DAPSONE, SOME QUINOLONES, SULFONAMIDES, ACYCLOVIR, METHOREXATE, NAPROXEN, KETOPROFEN, MECLOFENAMATE, LORAZEPAM, NITRAZEPAM,CAPTOPRIL, PARACETAMOL , SOME ANTIVIRALS LIKE ACYCLOVIR, GANCICLOVIR, ZIDOVUDINE, ZALCITABINE, FAMCICLOVIR & RIFAMPICIN SINCE PROBENECID DECREASES THE RENAL EXCRETION OF THESE DRUGS. DIURETICS & PYRAZINAMIDE INCREASE THE SERUM URIC ACID SO DOSE OF PROBENECID HAS TO BE INCREASED. PROBENECID MAY PROLONG OR ENHANCE THE ACTION OF ORAL SULFONYLUREAS. PATIENTS RECEIVING PROBENECID REQUIRE SIGNIFICANTLY LESS THIOPENTAL FOR INDUCTION OF ANESTHESIA. IN ADDITION, KETAMINE AND THIOPENTAL ANESTHESIA WERE SIGNIFICANTLY PROLONGED. PROBENECID HAS BEEN REPORTED TO INCREASE PLASMA CONCENTRATIONS OF METHOTREXATE. WHEN PROBENECID IS USED TO ELEVATE PLASMA CONCENTRATIONS OF PENICILLIN, OR OTHER BETA- LACTAMS, OR WHEN SUCH DRUGS ARE GIVEN TO PATIENTS TAKING PROBENECID THERAPEUTICALLY, HIGH PLASMA CONCENTRATIONS OF THE OTHER DRUG MAY INCREASE THE INCIDENCE OF ADVERSE REACTIONS ASSOCIATED WITH THAT DRUG. CO-ADMINISTRATION WITH KETOROLAC SHOULD BE AVOIDED.