Probenecid

A to Z Drug Facts

 Action Inhibits tubular reabsorption of urate, thus increasing urinary excretion of uric acid. Inhibits tubular secretion of most penicillin and cephalosporin antibiotics.

 Indications Treatment of hyperuricemia associated with gout and gouty arthritis; adjunctive therapy with penicillins or cephalosporins to elevate and prolong serum levels.

 Contraindications Children < 2 yr; blood dyscrasias or uric acid kidney stones. Do not start therapy until acute gout attack subsides.

 Route/Dosage

Gout

ADULTS & CHILDREN > 110 LB: PO 250 mg bid initially (for 1 wk), followed by 500 mg bid. Maintenance: May reduce by 500 mg q 6 mo until serum uric acid increases.

In Conjunction with Antibiotic Therapy: PO 2 g/day in divided doses. CHILDREN 2 to 14 YR (< 110 LB): PO 25 mg/kg or 0.7 g/m² initially. Maintenance: 40 mg/kg/day or 1.2 g/m², divided into 4 doses.

 Interactions Interacts with many other drugs by altering their clearance and elimination.

Barbiturate anesthetics, dyphylline, methotrexate, oral hypoglycemic agents, zidovudine: Increased serum levels and effects of these drugs. Salicylates: Inhibition of uricosuric effect of either drug.

 Lab Test Interferences May produce false-positive results for glycosuria in some urine glucose tests and falsely high assays for theophylline with Schack and Waxler technique. May inhibit renal excretion of phenosulfophthalein, 17-ketosteroids and sulfobromophthalein.

 Adverse Reactions

CNS: Headaches; dizziness. DERM: Dermatitis; pruritus. GI: Anorexia; nausea; GI distress; vomiting; sore gums. GU: Urinary frequency; hematuria; renal colic; nephrotic syndrome. HEMA: Anemia; hemolytic anemia (possibly related to G-6-PD deficiency); aplastic anemia. HEPA: Hepatic necrosis. OTHER: Hypersensitivity reactions; anaphylaxis; fever; flushing; exacerbation of gout; uric acid stones; costovertebral pain.

 Precautions

Pregnancy: Pregnancy category undetermined. Probenecid crosses placenta and appears in cord blood. Children: Not recommended for children < 2 yr. Alkalinization of urine: May be needed to prevent hematuria, renal colic, costovertebral pain, formation of uric acid stones. Exacerbation of gout: May occur; appropriate drug therapy (eg, colchicine or other appropriate therapy) is advisable. History of peptic ulcer: Use with caution. Hypersensitivity: Severe allergic reactions and anaphylaxis, although rare, have occurred. These have usually been associated with prior probenecid use. Renal impairment: May require increased doses for gout (not to exceed 2 g/day). Probenecid may be ineffective in chronic renal insufficiency (ie, glomerular filtration rate of < 30 ml/min). Drug is not recommended for use with penicillin in cases of known renal impairment.

 Administration/Storage

• Do not start therapy during acute gout attack; wait until attack subsides.
• Give with food or antacid to reduce GI upset.
• Colchicine is sometimes prescribed concurrently for first 3 to 6 mo of therapy since probenecid alone may aggravate gout.

 Assessment/Interventions

• Obtain patient history, including drug history and any known allergies. Note renal impairment, blood dyscrasias, peptic ulcers, or uric acid kidney stones.
• Encourage liberal fluid intake and give sodium bicarbonate or potassium citrate to prevent urate crystallization in kidney.
• Monitor BUN and renal function test results.
• Monitor for GI tolerance. If nausea, vomiting, or diarrhea becomes problem, notify physician.
• Observe for possible exacerbation of gout. If symptoms of exacerbation occur, notify physician; adjunctive therapy may be needed.
• Observe for possible allergic reaction. If reaction occurs, withhold drug and notify physician.

 Patient/Family Education

• Instruct patient to take drug with food or antacids if GI upset occurs.
• Advise patient that drinking 6 to 8 full glasses of water daily may help prevent formation of kidney stones.
• If physician has recommended restriction of intake of foods high in purine, review foods to be avoided (eg, organ meats, meat gravy, anchovies, sardines). Explain that moderate amounts of purine are found in other meats, fish and other seafood, asparagus, spinach, peas, dried legumes, and wild game.
• Inform patient to notify physician if GI upset, anorexia, or headaches become bothersome.
• Instruct patient to report the following symptoms to physician: Painful urination, bloody urine, severe lower back pain, difficulty breathing, or rash.
• Advise patient to avoid intake of alcoholic beverages.
• Instruct patient not to take otc medications (including aspirin) without consulting physician.
• Caution patient not to discontinue drug without consulting physician.

Books@Ovid
Copyright © 2003 Facts and Comparisons
David S. Tatro
A to Z Drug Facts