Source: Medicines and Medical Devices Safety Authority (NZ) Revision Year: 2018 Publisher: AFT Pharmaceuticals Ltd, PO BOX 33203, Takapuna, Auckland, Email: customer.service@aftpharm.com
Pharmacotherapeutic group: Antigout preparations
ATC code: M04AB01
Probenecid is a uricosuric and renal tubular blocking agent. It inhibits the tubular reabsorption of urate, thus increasing the urinary excretion of uric acid and decreasing serum urate levels. Effective uricosuria reduces the miscible urate pool, retards urate deposition, and promotes resorption of urate deposits.
Despite pronounced uricosuric activity, time is required to achieve clinical results. Acute attacks of gout may occur during the early phase of therapy in spite of the return to normal of the serum uric acid level. However, with continued use for some months, attacks of acute gout become less frequent and less intense.
As urate deposits in periarticular and articular structures are reabsorbed, joint pain is relieved, greater articular mobility is achieved, and further joint destruction may be averted. As urate deposits are mobilised from the gouty kidney, renal function may improve and further destructive changes may be prevented.
Probenecid inhibits the tubular reabsorption of phosphorus in hypoparathyroid but not in europarathyroid individuals.
Probenecid is completely absorbed after oral administration. Peak plasma levels are reached in two to four hours.
Between 85 and 95% of probenecid is bound to plasma albumin; the apparent volume of distribution of the drug is 11 litres.
Metabolism involves oxidation of alkyl side chains and glucuronide conjugation. The major metabolite, probenecid acyl glucuronide, accounts for close to 50% of the dose.
Approximately equal amounts (10-15%) of mono-n-propyl, secondary alcohol and carboxylic acid metabolites are excreted. The primary alcohol metabolite is not found in measurable amounts. The plasma half-life is between six and twelve hours, and increases with increasing dose (over the therapeutic dosage range) due to non-linear disposition.
Probenecid is excreted both by glomerular filtration (unbound fraction only) and by active secretion by the proximal renal tubule. Following oral administration, 75 – 88% of the dose is found in the urine mainly as metabolites and as lesser amounts of unchanged drug. The urinary excretion of unchanged probenecid is dependent on both the pH and flow rate of urine.
Not data available.
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