Probenecid

Medical uses

Probenecid is primarily used to treat gout and hyperuricemia.

Probenecid is sometimes used to increase the concentration of some antibiotics. 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.

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.

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).

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.