Probenecid
Probenecid, also sold under the brand name Probalan, is a medication that increases uric acid excretion in the urine. It is primarily used in treating gout and hyperuricemia. Probenecid was developed as an alternative to caronamide to competitively inhibit renal excretion of some drugs, thereby increasing their plasma concentration and prolonging their effects. Medical uses. Probenecid is primarily used to treat gout and hyperuricemia. Probenecid is sometimes used to increase the concentration of some antibiotics and to protect the kidneys when given with cidofovir. Specifically, a small amount of evidence supports the use of intravenous cefazolin once rather than  three times a day when it is combined with probenecid. It has also found use as a masking agent, potentially helping athletes using performance-enhancing substances to avoid detection by drug tests. Adverse effects. Mild symptoms such as nausea, loss of appetite, dizziness, vomiting, headache, sore gums, or frequent urination are common with this medication. Life-threatening side effects such as thrombocytopenia, hemolytic anemia, leukemia and encephalopathy are extremely rare. Theoretically probenecid can increase the risk of uric acid kidney stones. Drug interactions. Some of the important clinical interactions of probenecid include those with captopril, indomethacin, ketoprofen, ketorolac, naproxen, cephalosporins , quinolones, penicillins, methotrexate, zidovudine, ganciclovir, lorazepam, and acyclovir. In all these interactions, the excretion of these drugs is reduced due to probenecid, which in turn can lead to increased concentrations of these. Pharmacology. Probenecid probably has several pharmacological targets, including blocking pannexins. Probenecid is also useful in the treatment of gout where the mechanism of action is believed to be focused on the kidney. Probenecid interferes with the kidneys' organic anion transporter (OAT), which reclaims uric acid from the urine and returns it to the plasma. If probenecid (an organic acid) is present, the OAT binds preferentially to it (instead  of to uric acid), preventing reabsorption of the uric acid. Hence, the urine retains more uric acid, lowering uric acid concentration in the plasma. This is a good example of a medical usage for competition between substrates transported across cell membranes. This same effect, however, alters excretion of acidic drugs by the kidney, leading to the many drug interactions noted above. Pharmacokinetics. In the kidneys, probenecid is filtered at the glomerulus, secreted in the proximal tubule and reabsorbed in the distal tubule. History. During World War II, probenecid was used to extend limited supplies of penicillin; this use exploited probenecid 's interference with drug elimination (via urinary excretion) in the kidneys and allowed lower doses of penicillin to be used. Probenecid was added to the International Olympic Committee's list of banned substances in January 1988. In 2021, a study reported that the drug had broad antiviral properties.