Efficacy and Safety of Using MPC-5971 in Subjects Undergoing Shock Wave Lithotripsy

Inclusion criteria: * Male or female subject aged \> or equal to 18 to \< or equal to 70. * Subject has undergone a computerized tomography (CT) scan within 30 days of the screening visit. * Subject has been diagnosed with single unilateral renal calculus (target treatment stone). * Target treatment stone, is presumed to be of calcium composition and/or uric acid composition. * Target treatment stone is between \> or equal to 5 and \< or equal to 15 mm in diameter. * Contra lateral kidney may hold a clinically inconsequential size calculus that does not require concurrent SWL treatment. * Both kidneys are anatomically normal. * An appropriate candidate for SWL, determined by treating physician. * Female subjects with a negative pregnancy test, hysterectomy, tubal ligation or non-child bearing potential (post-menopausal). * Female subjects of child bearing potential with a negative pregnancy test and taking appropriate birth control for the duration of the study. * Urine is pyuria negative and nitrite negative on dipstick and/or negative upon microscopic evaluation. * Subject must voluntarily consent to participate in this study and provide his/her written informed consent prior to start of any study-specific procedures. Exclusion Criteria: * Current or past history of cystine stones or infection stones. * Renal insufficiency, defined as serum creatinine value outside of the normal reference range. * Currently has or had hyperkalemia within the past six months, defined as serum potassium outside of the normal reference range. * Currently has or had hypermagnesemia within the past six months, defined as serum magnesium outside of the normal reference range. * Active urinary tract infection. * Renal calculi in an anatomically abnormal kidney; horseshoe shape, ureteropelvic junction obstruction or calyceal diverticulum. * Altered urinary tract anatomy such as a transplant kidney, urinary reconstruction or congenital anomaly. * Blood coagulopathies and or taking anticoagulants (warfarin, coumarin, heparin). * Taking salicylate (aspirin), including low dose aspirin for cardio-prophylaxis or other NSAID (OTC) that may increase bleeding time, within the past 7 days. * History of complications with previous SWL; pyelonephritis, perinephric hematoma. * Unsuccessful SWL treatments for previous stone within the past six months. * Currently has or previously had ulcers of the esophagus, stomach and/or small intestines. * Chronic diarrhea or has a history of diarrhea. * Bowel disease such as Crohn's disease, Celiac disease, fat malabsorption or Sprue. * Undergone any bariatric surgery procedures. * Obese, defined as BMI \>30. * Uncontrolled hypertension defined as subjects taking medication specific for hypertension or subject not on medication with systolic blood pressure above 140 and diastolic above 90. * Adrenal insufficiency (i.e., Addison's disease), adrenal tumors, and/or subjects on adrenal hormone replacement therapy. * Taking potassium-sparing diuretics (triamterene, amiloride, spironolactone, Midamor®, Aldactone®, Dyrenium®, Eplerenone®). * Taking potassium supplements (Rx or OTC) within the past 15 days. * Taking magnesium supplements (Rx or OTC) within the past 15 days. * Taken potassium citrate supplements (Rx or OTC) within the past 30 days. * Subject taking anticholinergic medications at entry (dicyclomine, atropine, scopolamine, oxybutynin, tolerodine, Cogentin®, Sinemet®, Robinal®, Kenadrin®, Artane®, Enablex®, Detrol®, Vesicare®, Sanctura®, Ditropan®, Oxytrol®, Bentyl®, Byclomine®, Dibent®, Di-Spaz®, or Dilomine®). (Subjects may be prescribed anticholinergics as standard of care with use of stents post entry.) * Subject is has taken gastrointestinal enzyme replacement therapy or proton pump inhibitors within past 30 days (Ultrase®, Creon®, Viokase®, Pancrease® MT, pancrelipase agents, Aciphex®, Nexium®, Prevacid®, Protonix®, Zegerid® Prilosec OTC®, Kapidex®, rabeprazole, esomeprazole, lansoprazole, pantoprazole, omeprazole, dexlansoprazole). * Women who are pregnant or lactating. * Subjects with a known hypersensitivity to potassium, magnesium, citrate or any excipients in the drug formulation