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Probenecid
Probenecid (Benemid)
Probenecid
(proh-BEN-ih-sid)
Pregnancy Category: B Benemid Benuryl (Rx)

Classification: Antigout agent, uricosuric agent

Action/Kinetics: A uricosuric agent that increases the excretion of uric acid by inhibiting the tubular reabsorption of uric acid; this results in a decreased serum level of uric acid. Also inhibits the renal secretion of penicillins and cephalosporins; this effect is often taken advantage of in the treatment of infections because concomitant administration of probenecid will increase plasma levels of antibiotics. Peak plasma levels: 2-4 hr. Time to peak effect, uricosuric: 0.5 hr; for suppression of penicillin excretion: 2 hr. Therapeutic plasma levels for inhibition of antibiotic secretion: 40-60 mcg/mL; therapeutic plasma levels for uricosuric effect: 100-200 mcg/mL. t1/2: approximately 5-8 hr. Duration for inhibition of penicillin excretion: 8 hr. Metabolized in the liver to active metabolites; excreted in urine (5%-10% unchanged). Excretion is increased in alkaline urine.

Uses: Hyperuricemia in chronic gout and gouty arthritis. Adjunct in therapy with penicillins or cephalosporins to elevate and prolong plasma antibiotic levels.

Contraindications: Hypersensitivity to drug, blood dyscrasias, uric acid, and kidney stones. Use for hyperuricemia in neoplastic disease or its treatment. Use in children less than 2 years of age. Concomitant use of salicylates or use with penicillin in renal impairment.

Special Concerns: Use with caution in renal disease, porphyria, G6PD deficiency, history of allergy to sulfa drugs, and peptic ulcer.

Side Effects: CNS: Headaches, dizziness. GI: Anorexia, N&V;, diarrhea, constipation, and abdominal discomfort. Allergic: Skin rash, dermatitis, pruritus, drug fever, and rarely anaphylaxis. GU: Nephrotic syndrome, uric acid stones with or without hematuria, urinary frequency, renal colic or costovertebral pain. Miscellaneous: Flushing, hemolytic anemia (possibly related to G6PD deficiency) anemia, sore gums, hepatic necrosis, aplastic anemia.
Initially, the drug may increase frequency of acute gout attacks due to mobilization of uric acid.

Drug Interactions: Acyclovir / Renal excretion of acyclovir Allopurinol / Additive effects to uric acid serum levels AZT / Bioavailability of AZT; possible malaise, myalgia, fever Benzodiazepines / More rapid onset and longer duration of benzodiazepine effects Cephalosporins / Cephalosporin effect R/T kidney excretion Ciprofloxacin / 50% in systemic levels of ciprofloxacin Clofibrate / Clofibric acid (active) levels effects Dapsone / Dapsone effects Dyphylline / Dyphylline effect R/T kidney excretion Methotrexate / Methotrexate effect and toxicity R/T kidney excretion NSAIDs / NSAID effects R/T kidney excretion Pantothenic acid / Pantothenic acid effects Penicillamine / Penicillamine effects Penicillins / Pencillin effects R/T kidney excretion Pyrazinamide / Inhibits hyperuricemia produced by pyrazinamide Rifampin / Rifampin effects R/T kidney excretion Salicylates / Inhibits uricosuric activity of probenecid Sulfinpyrazone / Sulfinpyrazone effects R/T kidney excretion Sulfonamides / Sulfonamide effects R/T plasma protein binding Sulfonylureas, oral / Sulfonylurea effect hypoglycemia Thiopental / Thiopental effects

How Supplied: Tablet: 500 mg

Dosage
•Tablets Gout.
Adults, initial: 250 mg b.i.d. for 1 week. Maintenance: 500 mg b.i.d. Dosage may have to be increased further (by 500 mg/day q 4 weeks to maximum of 2 g) until urate excretion is less than 700 mg in 24 hr. Colbenemid, a combination tablet containing colchicine (0.5 mg) and probenecid (500 mg), is available.
Adjunct to penicillin or cephalosporin therapy.
Adults: 500 mg q.i.d. Dosage is decreased for elderly clients with renal damage. Pediatric, 2-14 years, initial: 25 mg/kg (or 700 mg/m²); maintenance, 10 mg/kg q.i.d. (or 300 mg/m² q.i.d.). For children 50 kg or more: give adult dosage.
Gonorrhea, uncomplicated.
Adults: 1 g (as a single dose) 30 min before 4.8 million units of penicillin G procaine aqueous; pediatric, less than 45 kg: 25 mg/kg (up to a maximum of 1 g) with appropriate antibiotic therapy.
Neurosyphilis.
Adults: 0.5 g q.i.d. with penicillin G procaine aqueous, 2.4 million units/day IM, both for 10-14 days.
Pelvic inflammatory disease.
Adults: 1 g (as a single dose) plus cefoxitin, 2 g IM given concurrently.