What is the use and dosage of Triamterene in treating edema and hypertension?

Triamterene for Edema and Hypertension

Triamterene is a potassium-sparing diuretic indicated for treating edema associated with congestive heart failure, cirrhosis, nephrotic syndrome, and hypertension, with a standard adult dosage of 100 mg twice daily after meals, not exceeding 300 mg daily. 1

Mechanism and Clinical Use

Triamterene works by inhibiting the epithelial sodium channel (ENaC) in the distal convoluted tubule and collecting duct of the kidney, which:

• Reduces sodium reabsorption and potassium secretion
• Produces mild diuresis and natriuresis
• Conserves potassium, preventing hypokalemia

Dosage Guidelines

Adults:

• Initial dose: 100 mg twice daily after meals 1
• Maximum daily dose: 300 mg 1
• Maintenance dose: Titrated based on clinical response

Children:

• Initial dose: 1-2 mg/kg/day 2
• Maximum dose: 3-4 mg/kg/day up to 300 mg/day 2
• Dosing frequency: Twice daily (BID) 2

Clinical Indications

Triamterene is indicated for:

1. Edema associated with:

   • Congestive heart failure
   • Cirrhosis of the liver
   • Nephrotic syndrome
   • Steroid-induced edema
   • Idiopathic edema
   • Secondary hyperaldosteronism 1

2. Hypertension:

   • As monotherapy (though less common)
   • In combination with other antihypertensives, particularly thiazide diuretics 3

Combination Therapy

Triamterene is often used in combination therapy:

1. With thiazide diuretics:

   • Enhances blood pressure-lowering effect (3-4 mmHg additional reduction) 3
   • Counteracts thiazide-induced hypokalemia 4
   • Creates synergistic diuretic effect 5

2. For resistant edema:

   • Can be combined with loop diuretics for enhanced effect 2
   • Particularly useful in patients refractory to other diuretics 5

Monitoring and Precautions

Required Monitoring:

• Serum electrolytes (particularly potassium)
• Renal function
• Blood pressure
• Clinical signs of fluid retention

Precautions:

1. Hyperkalemia risk:

   • Avoid concurrent use with other potassium-sparing diuretics 2
   • Discontinue all potassium supplements when starting triamterene 1
   • Use with caution when combined with ACE inhibitors or ARBs 2

2. Renal considerations:

   • Risk of acute kidney injury, especially with NSAIDs 6
   • Potential for nephrolithiasis and interstitial nephritis 6
   • Use with caution in patients with renal impairment

3. Pregnancy considerations:

   • Not recommended for routine use in healthy pregnant women
   • May be appropriate for pathological edema in pregnancy 1

Clinical Pearls

1. Potassium management:

   • When adding triamterene to existing diuretic therapy, discontinue all potassium supplementation 1
   • Monitor serum potassium closely, especially when combined with ACE inhibitors or ARBs

2. Blood pressure effect:

   • Beyond its potassium-sparing properties, triamterene independently enhances blood pressure reduction when combined with hydrochlorothiazide 3

3. Resistant edema:

   • Particularly valuable in long-term management of chronic edema resistant to other diuretics 5
   • Effective in patients with secondary hyperaldosteronism 1

4. Drug interactions:

   • Avoid concurrent use with NSAIDs due to risk of acute kidney injury 6
   • Use caution when combining with ACE inhibitors or ARBs due to hyperkalemia risk 2

Triamterene remains a valuable option in managing edema and hypertension, particularly when potassium conservation is desired or when enhanced diuretic effect is needed in combination therapy.