Urocit-K - Drug Monograph

Introduction

Urocit-K (potassium citrate) is an oral alkalinizing agent used primarily for the management of renal tubular acidosis with calcium stones, hypocitraturic calcium oxalate nephrolithiasis, and uric acid lithiasis with or without calcium stones. It works by increasing urinary citrate levels and raising urinary pH, creating an environment less favorable for stone formation.

Mechanism of Action

Urocit-K exerts its therapeutic effects through two primary mechanisms: 1. Urinary Alkalinization: Potassium citrate is metabolized to potassium bicarbonate, which acts as a systemic and urinary alkalinizer, increasing urinary pH 2. Citrate Supplementation: Provides citrate, which complexes with calcium in urine, reducing calcium oxalate and calcium phosphate supersaturation and inhibiting crystal formation and growth

The increased urinary citrate concentration serves as an inhibitor of calcium crystal aggregation, while the elevated pH helps dissolve existing uric acid stones and prevents new stone formation.

Indications

• FDA-approved:

- Management of renal tubular acidosis with calcium stones - Hypocitraturic calcium oxalate nephrolithiasis - Uric acid lithiasis with or without calcium stones

• Off-label uses:

- Prevention of contrast-induced nephropathy (limited evidence) - Adjuvant therapy in gout management - Management of metabolic acidosis in chronic kidney disease

Dosage and Administration

• Initial: 10 mEq three times daily
• Increase by 10 mEq increments at 3-4 week intervals
• Maximum dose: 100 mEq daily in divided doses

• Renal impairment: Use with caution; contraindicated in severe renal impairment
• Hepatic impairment: No dosage adjustment required
• Elderly: Start at lower end of dosing range
• Pediatric: Safety and effectiveness not established

Pharmacokinetics

• Absorption: Rapidly absorbed from gastrointestinal tract
• Distribution: Distributed throughout extracellular fluid
• Metabolism: Converted to potassium bicarbonate in the body
• Elimination: Primarily renal excretion; potassium is filtered and reabsorbed in the nephron
• Onset of action: Urinary pH changes occur within 1-2 hours
• Duration: Effects persist for 3-4 hours after administration

Contraindications

• Severe renal impairment with oliguria or azotemia
• Untreated Addison's disease
• Hyperkalemia (serum potassium >5.5 mEq/L)
• Severe cardiac dysfunction
• Patients on potassium-sparing diuretics
• Active peptic ulcer disease
• Esophageal compression due to enlarged left atrium

Warnings and Precautions

• Hyperkalemia: Monitor serum potassium regularly, especially in patients with renal impairment, diabetes, or heart failure
• GI effects: May cause gastrointestinal irritation; use caution in patients with GI motility disorders
• Metabolic alkalosis: Monitor for signs of alkalosis with high doses
• Renal function: Regular monitoring of renal function required
• Drug-form interactions: Tablets may expand and cause GI obstruction if not swallowed properly

Drug Interactions

• Potassium-sparing diuretics (spironolactone, triamterene, amiloride): Increased risk of hyperkalemia
• ACE inhibitors/ARBs: Increased risk of hyperkalemia
• NSAIDs: May reduce renal potassium excretion
• Anticholinergics: May delay tablet transit, increasing risk of GI injury
• Sodium bicarbonate: Additive alkalinizing effects
• Lithium: May increase lithium excretion

Adverse Effects

• Gastrointestinal discomfort
• Nausea
• vomiting
• Diarrhea
• Abdominal pain

• Hyperkalemia (especially in at-risk patients)
• Metabolic alkalosis
• Flatulence

• GI ulceration or perforation
• Esophageal irritation or injury
• Allergic reactions

Monitoring Parameters

• Baseline: Serum electrolytes (especially potassium), renal function, arterial blood gas if indicated
• During therapy:

- Serum potassium every 3-6 months - Renal function every 6-12 months - Urinary pH (target: 6.0-7.0) - 24-hour urinary citrate (target: >320 mg/day) - Clinical signs of hyperkalemia or alkalosis

Patient Education

• Take with meals to minimize gastrointestinal upset
• Swallow tablets whole with a full glass of water
• Do not crush, chew, or suck tablets
• Report signs of hyperkalemia (muscle weakness, irregular heartbeat)
• Maintain adequate fluid intake (2-3 L/day)
• Follow dietary recommendations provided by healthcare provider
• Keep regular follow-up appointments for monitoring
• Inform all healthcare providers about Urocit-K use

References

1. Package Insert: Urocit-K (potassium citrate) Extended-Release Tablets. Mission Pharmacal Company. 2. Asplin JR. Evaluation of the kidney stone patient. Semin Nephrol. 2008;28(2):117-122. 3. Pearle MS, Goldfarb DS, Assimos DG, et al. Medical management of kidney stones: AUA guideline. J Urol. 2014;192(2):316-324. 4. Moe OW. Kidney stones: pathophysiology and medical management. Lancet. 2006;367(9507):333-344. 5. Phillips R, Hanchanale VS, Myatt A, Somani B, Nabi G, Biyani CS. Citrate salts for preventing and treating calcium containing kidney stones in adults. Cochrane Database Syst Rev. 2015;(10):CD010057. 6. Kidney Disease: Improving Global Outcomes (KDIGO) CKD-MBD Work Group. KDIGO clinical practice guideline for the diagnosis, evaluation, prevention, and treatment of Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD). Kidney Int Suppl. 2009;(113):S1-S130.