POTASSIUM CITRATE

Potassium citrate extended-release tablets are a citrate salt of potassium. Its empirical formula is K 3 C 6 H 5 O 7 • H 2 O, and it has the following chemical structure: Potassium citrate extended-release tablets are off white to tan yellowish, oral wax-matrix tablets, contain 5 mEq (540 mg) potassium citrate, 10 mEq (1080 mg) potassium citrate and 15 mEq (1620 mg) potassium citrate each. Inactive ingredients include carnauba wax, silicon dioxide and magnesium stearate. FDA approved dissolution test specifications differ from USP. structure

Potassium citrate extended-release tablets are a citrate salt of potassium indicated for the management of: Renal tubular acidosis (RTA) with calcium stones (1.1) Hypocitraturic calcium oxalate nephrolithiasis of any etiology (1.2) Uric acid lithiasis with or without calcium stones (1.3) 1.1 Renal Tubular Acidosis (RTA) with Calcium Stones Potassium citrate is indicated for the management of renal tubular acidosis [see Clinical Studies (14.1)]. 1.2 Hypocitraturic Calcium Oxalate Nephrolithiasis of any Etiology Potassium citrate is indicated for the management of Hypocitraturic calcium oxalate nephrolithiasis [see Clinical Studies (14.2)] . 1.3 Uric Acid Lithiasis with or without Calcium Stones Potassium citrate is indicated for the management of Uric acid lithiasis with or without calcium stones [see Clinical Studies (14.3)].

Objective: To restore normal urinary citrate (greater than 320 mg/day and as close to the normal mean of 640 mg/day as possible), and to increase urinary pH to a level of 6.0 to 7.0. Severe hypocitraturia (urinary citrate < 150 mg/day): therapy should be initiated at 60 mEq per day; a dose of 30 mEq two times per day or 20 mEq three times per day with meals or within 30 minutes after meals or bedtime snack (2.2) Mild to moderate hypocitraturia (urinary citrate >150 mg/day): therapy should be initiated at 30 mEq per day; a dose of 15 mEq two times per day or 10 mEq three times per day with meals or within 30 minutes after meals or bedtime snack (2.3) 2.1 Dosing Instructions Treatment with extended release potassium citrate should be added to a regimen that limits salt intake (avoidance of foods with high salt content and of added salt at the table) and encourages high fluid intake (urine volume should be at least two liters per day). The objective of treatment with potassium citrate extended-release tablets is to provide potassium citrate in sufficient dosage to restore normal urinary citrate (greater than 320 mg/day and as close to the normal mean of 640 mg/day as possible), and to increase urinary pH to a level of 6.0 or 7.0. Monitor serum electrolytes (sodium, potassium, chloride and carbon dioxide), serum creatinine and complete blood counts every four months and more frequently in patients with cardiac disease, renal disease or acidosis. Perform electrocardiograms periodically. Treatment should be discontinued if there is hyperkalemia, a significant rise in serum creatinine or a significant fall in blood hematocrit or hemoglobin. 2.2 Severe Hypocitraturia In patients with severe hypocitraturia (urinary citrate < 150 mg/day), therapy should be initiated at a dosage of 60 mEq/day (30 mEq two times/day or 20 mEq three times/day with meals or within 30 minutes after meals or bedtime snack). Twenty-four hour urinary citrate and/or urinary pH measurements should be used to determine the adequacy of the initial dosage and to evaluate the effectiveness of any dosage change. In addition, urinary citrate and/or pH should be measured every four months. Doses of potassium citrate extended-release tablets greater than 100 mEq/day have not been studied and should be avoided. 2.3 Mild to Moderate Hypocitraturia In patients with mild to moderate hypocitraturia (urinary citrate > 150 mg/day) therapy should be initiated at 30 mEq/day (15 mEq two times/day or 10 mEq three times/day with meals or within 30 minutes after meals or bedtime snack). Twenty-four hour urinary citrate and/or urinary pH measurements should be used to determine the adequacy of the initial dosage and to evaluate the effectiveness of any dosage change. Doses of potassium citrate extended-release tablets greater than 100 mEq/day have not been studied and should be avoided.

Potassium citrate extended-release tablets are contraindicated: In patients with hyperkalemia (or who have conditions predisposing them to hyperkalemia), as a further rise in serum potassium concentration may produce cardiac arrest. Such conditions include: chronic renal failure, uncontrolled diabetes mellitus, acute dehydration, strenuous physical exercise in unconditioned individuals, adrenal insufficiency, extensive tissue breakdown or the administration of a potassium-sparing agent (such as triamterene, spironolactone or amiloride). In patients in whom there is cause for arrest or delay in tablet passage through the gastrointestinal tract, such as those suffering from delayed gastric emptying, esophageal compression, intestinal obstruction or stricture, or those taking anticholinergic medication. In patients with peptic ulcer disease because of its ulcerogenic potential. In patients with active urinary tract infection (with either urea-splitting or other organisms, in association with either calcium or struvite stones). The ability of potassium citrate extended-release tablets to increase urinary citrate may be attenuated by bacterial enzymatic degradation of citrate. Moreover, the rise in urinary pH resulting from potassium citrate therapy might promote further bacterial growth. In patients with renal insufficiency (glomerular filtration rate of less than 0.7 ml/kg/min), because of the danger of soft tissue calcification and increased risk for the development of hyperkalemia. Patients with hyperkalemia (or who have conditions predisposing them to hyperkalemia). Such conditions include chronic renal failure, uncontrolled diabetes mellitus, acute dehydration, strenuous physical exercise in unconditioned individuals, adrenal insufficiency, extensive tissue breakdown (4) Patients for whom there is cause for arrest or delay in tablet passage through the gastrointestinal tract such as those suffering from delayed gastric emptying, esophageal compression, intestinal obstruction or stricture (4) Patients with peptic ulcer disease (4) Patients with active urinary tract infection (4) Patients with renal insufficiency (glomerular filtration rate of less than 0.7 ml/kg/min) (4)

Some patients may develop minor gastrointestinal complaints such as abdominal discomfort, vomiting, diarrhea, loose bowel movements or nausea. These may be alleviated by taking the dose with meals or snacks or by reducing the dosage (6.1) To report SUSPECTED ADVERSE REACTIONS, contact Camber Pharmaceuticals, Inc., at 1-866-495-8330 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Postmarketing Experience Some patients may develop minor gastrointestinal complaints during potassium citrate therapy, such as abdominal discomfort, vomiting, diarrhea, loose bowel movements or nausea. These symptoms are due to the irritation of the gastrointestinal tract, and may be alleviated by taking the dose with meals or snacks, or by reducing the dosage. Patients may find intact matrices in their feces.

The following drug interactions may occur with potassium citrate: Potassium-sparing diuretics: concomitant administration should be avoided since the simultaneous administration of these agents can produce severe hyperkalemia (7.1) Drugs that slow gastrointestinal transit time: These agents (such as anticholinergics) can be expected to increase the gastrointestinal irritation produced by potassium salts (7.2) Renin-angiotensin-aldosterone inhibitors: Monitor for hyperkalemia (7.3) Nonsteroidal Anti-inflammatory drugs (NSAIDs) monitor for hyperkalemia (7.4) 7.1 Potential Effects of Potassium Citrate on Other Drugs Potassium-sparing Diuretics: Concomitant administration of potassium citrate and a potassium-sparing diuretic (such as triamterene, spironolactone or amiloride) should be avoided since the simultaneous administration of these agents can produce severe hyperkalemia. 7.2 Potential Effects of Other Drugs on Potassium Citrate Drugs that slow gastrointestinal transit time: These agents (such as anticholinergics) can be expected to increase the gastrointestinal irritation produced by potassium salts. 7.3 Renin-Angiotensin-Aldosterone System Inhibitors Drugs that inhibit the renin-angiotensin-aldosterone system (RAAS) including angiotensin converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs), spironolactone, eplerenone, or aliskiren produce potassium retention by inhibiting aldosterone production. Closely monitor potassium in patients receiving concomitant RAAS therapy. 7.4 Nonsteroidal Anti-Inflammatory Drugs (NSAIDs) NSAIDs may produce potassium retention by reducing renal synthesis of prostagladin E and impairing the renin-angiotensin system. Closely monitor potassium in patients on concomitant NSAIDs.