Why is probenecid given before the administration of penicillin?

Probenecid is administered before the administration of penicillin primarily to prevent the excretion of penicillin and thereby prolong its action in the body. Penicillin is eliminated from the body mainly through the kidneys, and probenecid inhibits the renal tubular secretion of penicillin. This means that when probenecid is given, it allows penicillin to remain in the bloodstream longer by reducing its rate of removal from the system. As a result, probenecid effectively enhances the therapeutic effects of penicillin, allowing for more sustained levels of the antibiotic.

The other options do not accurately reflect the primary purpose of administering probenecid with penicillin, as it is not related to increasing the dosage, preventing allergic reactions, or enhancing absorption of the drug.