Medication Summary
When pharmacologic therapy is warranted, the most successful method of oral chemolysis is to administer a urease inhibitor. Urinary irrigants may also be used to solubilize and dissolve certain types of calculi.
Urease Inhibitors
Class Summary
These agents inhibit the hydrolysis of urea and the production of ammonia.
Acetohydroxamic acid (Lithostat)
Reversibly inhibits bacterial enzyme urease, thereby inhibiting hydrolysis of urea and production of ammonia in urine infected with urea-splitting organisms. Reduced ammonia levels and decreased pH enhance effectiveness of antimicrobial agents and increase cure rate of these infections. Does not acidify urine directly, nor does it have direct antibacterial effect. In patients with urea-splitting urinary infections (often accompanied by struvite stone disease) that are recalcitrant to other management, reduces pathologically elevated urinary ammonia and pH levels.
Genitourinary Irrigants
Class Summary
Magnesium from the irrigating solution is exchanged for calcium within the stone. Additionally, the acidic pH of the solution is able to solubilize and dissolve magnesium stones.
Citric acid/glucono-delta-lactone/magnesium carbonate (Renacidin)
Action on susceptible apatite calculi results from exchange of magnesium from irrigating solution for insoluble calcium contained in stone matrix or calcification. Magnesium salts thereby formed are soluble in gluconocitrate irrigating solution, resulting in dissolution of calculus. Struvite calculi are composed mainly of magnesium ammonium phosphates, which are solubilized by hemiacidrin due to acidic pH. Essential that patients be free from urinary tract infections prior to initiating chemolytic therapy. Used for local irrigation dissolution of renal calculi composed of apatite (a calcium carbonate-phosphate compound) or struvite (magnesium ammonium phosphates) in patients who are not candidates for surgical removal of calculi. Also used as adjunctive therapy to dissolve residual apatite or struvite calculi and fragments after surgery or to achieve partial dissolution of renal calculi to facilitate surgical removal.
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Struvite and staghorn calculi. Plain abdominal radiograph demonstrating a right staghorn calculus and a smaller left renal pelvic stone. The patient is a 72-year-old woman.
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Struvite and staghorn calculi. Plain abdominal radiograph of a 72-year-old woman. She underwent right percutaneous nephrolithotomy, with the path of renal access demonstrated by the remaining nephrostomy tube. She was rendered stone free in the single-session procedure.
