Medication Summary

The goals of pharmacotherapy are to reduce morbidity and to prevent complications.

Allopurinol has been associated with the development of hemorrhagic skin lesions, exfoliation, and a rare fatal systemic vasculitis. Pruritus often precedes the development of rash and should prompt patients to discontinue the medication. Alterations in hepatic function and jaundice have been reported with allopurinol use; these complications require monitoring of serum liver function test results soon after the institution of therapy. Allopurinol may result in an acute gouty attack in patients with hyperuricemia.

Class Summary

The most important medications used for the dissolution or prevention of uric acid urinary stones are alkalinizing agents (eg, potassium citrate) to increase the urinary pH to 6.5-7.0. Balanced citrate alkali (eg, potassium citrate; Urocit-K, Polycitra-K) are the most commonly used medications. Sodium and potassium bicarbonate are also used frequently. One disadvantage of sodium alkali is that the increased sodium and fluid load may be detrimental to patients with renal failure, liver failure, or congestive heart failure.

Alternatively, citrate supplementation may be given. Citrate inhibits calcium oxalate crystallization directly and by complexing with calcium in solution to reduce its concentration and availability. Potassium citrate is preferred over sodium citrate because it is not associated with a sodium load. Potassium citrate comes in a slow-release wax-based tablet, which may be seen as an intact tablet in the stool; however, the citrate has been absorbed. Patients should be warned that this may occur.

For patients who are not tolerant of or compliant with a frequent dosing schedule, a single evening dose may be quite beneficial to increase the urinary pH (alkaline tide) overnight.

Potassium citrate can also be given as a crystal preparation. The advantage of this preparation is that it forces patients to increase their fluid intake. Potassium citrate may be given in liquid preparations, with and without glucose additives. Finally, lemonade has been shown to increase urinary citrate levels and is an alternative or supplement to pharmacologic formulations.

The primary treatment for uric acid stones is urinary alkalinization. Surprisingly, it is not associated with hypocitraturia. Allopurinol should be added to the therapeutic regimen in the presence of associated hyperuricemia, hyperuricosuric calcium stone disease, intolerance of alkali, or continuing uric acid stone production despite alkalinization therapy. Initial dosing should be 300 mg/d.

Potassium citrate (Urocit-K, Polycitra-K)

Available as tab, syr, and crystals. All forms should be taken with water or juice according to directions.

Potassium bicarbonate/potassium citrate (Effer-K, K-Ide, Klor-Con/EF, K-Lyte)

View full drug information

Needed for conduction of nerve impulses in heart, brain, and skeletal muscle. Helps maintain normal renal function. Plays role in contraction of cardiac, skeletal, and smooth muscles. All PO forms of potassium bicarbonate should be taken with adequate fluids according to directions.

Sodium bicarbonate (Neut)

View full drug information

Excellent urinary alkalinization agent. Dissociates to provide bicarbonate ion, which neutralizes hydrogen ion concentration and raises blood and urinary pH.

Class Summary

In cases of hyperuricemia or significant hyperuricosuria, allopurinol is effective. This drug inhibits the conversion of hypoxanthine and xanthine to uric acid. In patients with hyperuricosuric calcium stones, treatment involves reducing the monosodium urate–induced calcium oxalate crystallization. This is accomplished by decreasing urinary uric acid excretion and limiting dietary sodium intake (< 150 mEq/d). Patients should initially be treated with dietary purine and sodium restriction. In approximately 30% of patients, hyperuricosuria is due to uric acid overproduction and does not improve with dietary restriction. In this situation and in patients intolerant of diet restriction, allopurinol is the medication of choice.

Allopurinol (Zyloprim)

View full drug information

Inhibits xanthine oxidase, the enzyme that synthesizes uric acid from hypoxanthine. Reduces the synthesis of uric acid without disrupting the biosynthesis of vital purines.

Media Gallery

CT scan demonstrating right partial staghorn uric acid calculus. Uric acid stones appear dense on CT scan and radiolucent on kidneys, ureters, and bladder (KUB) imaging (not shown).
Follow-up CT scan of patient in the image above (ie, with partial staghorn uric acid calculus) 1 year later. This patient was treated with oral urinary alkalinization with sodium bicarbonate. Note only a small residual fragment is present (right image).

of 2

Author

Bijan Shekarriz, MD Director, Laparoscopy and Minimally Invasive Surgery, Associate Professor of Urology, Department of Urology, State University of New York Upstate Medical University

Bijan Shekarriz, MD is a member of the following medical societies: American Urological Association, Endourological Society

Disclosure: Nothing to disclose.

Coauthor(s)

Marshall L Stoller, MD Professor and Vice Chairman, Medical Director of Urinary Stone Center, Department of Urology, University of California, San Francisco, School of Medicine

Marshall L Stoller, MD is a member of the following medical societies: American Urological Association

Disclosure: Nothing to disclose.

Brian H Eisner, MD Instructor in Surgery, Department of Urology, Massachusetts General Hospital-Harvard Medical School; Fellow in Endourology, Department of Urology, University of California

Brian H Eisner, MD is a member of the following medical societies: American Urological Association, Endourological Society

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Chief Editor

Bradley Fields Schwartz, DO, FACS Professor of Urology, Director, Center for Laparoscopy and Endourology, Department of Surgery, Southern Illinois University School of Medicine

Bradley Fields Schwartz, DO, FACS is a member of the following medical societies: American College of Surgeons, American Urological Association, Association of Military Osteopathic Physicians and Surgeons, Endourological Society, Society of Laparoendoscopic Surgeons, Society of University Urologists

Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: Endourological Society Board of Directors; President Elect North Central Section of the American Urological Association<br/>Serve(d) as a speaker or a member of a speakers bureau for: Cook Medical.

Additional Contributors

Allen Donald Seftel, MD Professor of Urology, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School; Head, Division of Urology, Director, Urology Residency Training Program, Cooper University Hospital

Allen Donald Seftel, MD is a member of the following medical societies: American Urological Association

Disclosure: Received consulting fee from lilly for consulting; Received consulting fee from abbott for consulting; Received consulting fee from auxilium for consulting; Received consulting fee from actient for consulting; Received honoraria from journal of urology for board membership; Received consulting fee from endo for consulting.