Moduretic

Active Ingredients & Dual Mechanism of Action

1. Hydrochlorothiazide (50 mg): A thiazide diuretic that inhibits the reabsorption of sodium and chloride in the distal convoluted tubules of the kidney. This causes increased excretion of water, sodium, and chloride, thereby reducing intravascular fluid volume and systemic vascular resistance.
2. Amiloride Hydrochloride (5 mg): A potassium-sparing (antikaliuretic) diuretic that acts on the late distal tubule and collecting duct to block sodium reabsorption while simultaneously inhibiting potassium secretion.

Dosage Forms & Available Strengths

• Moduretic 5 mg / 50 mg Tablets: Each tablet contains 5 mg anhydrous amiloride HCl and 50 mg hydrochlorothiazide.

Clinical Indications

• Essential Hypertension: Management of mild-to-moderate high blood pressure, especially in patients who are prone to developing hypokalemia on thiazide monotherapy.
• Congestive Heart Failure: Treatment of edema (fluid retention) associated with heart failure.
• Hepatic Cirrhosis with Ascites: Management of fluid accumulation in the abdominal cavity caused by severe liver disease.

Key Pharmacokinetics

• Onset of Action: Diuresis generally starts within 2 hours of oral ingestion.
• Duration of Action: Sustained therapeutic action for approximately 24 hours, supporting once-daily dosing regimens.
• Excretion: Hydrochlorothiazide and amiloride are excreted mostly unchanged by the kidneys.

Administration Guidelines

• Usage: Administered orally once daily (or as prescribed), typically taken in the morning with food to avoid gastrointestinal upset and prevent nocturnal urination.
• Dosage Adjustment: Initial therapy usually starts with 1 tablet daily (or half a tablet in sensitive populations), adjusted based on clinical response up to a maximum of 2 tablets daily.

Safety Profile & Considerations

• Common Side Effects: Dizziness, headache, nausea, fatigue, abdominal pain, diarrhea, and muscle cramps.
• Key Precautions & Warnings:
  • Hyperkalemia (High Blood Potassium): Due to amiloride, elevated serum potassium levels can occur, particularly in diabetic patients, the elderly, or those with impaired renal function. Routine blood electrolyte tests are required.
  • Dehydration & Electrolyte Imbalance: Risk of hyponatremia (low sodium) or hypomagnesemia.
• Contraindications:
  • Pre-existing hyperkalemia (serum potassium > 5.5 mEq/L).
  • Severe renal failure, acute kidney injury, or anuria.
  • Known hypersensitivity to amiloride, hydrochlorothiazide, or other sulfonamide-derived drugs.
  • Concomitant use with other potassium-sparing agents or potassium supplements.
• Key Interactions:
  • Potassium Supplements / Salt Substitutes: Should be avoided due to the severe risk of hyperkalemia.
  • ACE Inhibitors & ARBs: Simultaneous use increases the risk of hyperkalemia and requires close serum potassium monitoring.
  • Lithium: Thiazides reduce renal clearance of lithium, significantly elevating the risk of lithium toxicity.
  • NSAIDs: May reduce the blood pressure-lowering and diuretic efficacy of Moduretic while increasing the risk of acute renal dysfunction.

Note: Moduretic is a prescription-only medication. Treatment, dosage adjustments, and monitoring of renal function and blood electrolytes must be conducted under the direct supervision of a licensed healthcare professional.