Dyazide (Triamterene and Hydrochlorothiazide) Use and Dosage for Hypertension and Edema
Dyazide (triamterene 37.5 mg/hydrochlorothiazide 25 mg) is recommended for patients with hypertension at a standard dosage of one capsule once or twice daily, with a maximum of two capsules daily, particularly when potassium conservation is desired alongside blood pressure control.
Mechanism of Action and Formulation
Dyazide is a fixed-dose combination medication containing:
- Hydrochlorothiazide (25 mg): A thiazide diuretic that inhibits sodium reabsorption in the distal convoluted tubule
- Triamterene (37.5 mg): A potassium-sparing diuretic that blocks sodium channels in the collecting duct
This combination provides synergistic diuretic effects while minimizing potassium loss that typically occurs with thiazide diuretics alone.
Dosing Recommendations
For Hypertension:
- Initial dose: One capsule (triamterene 37.5 mg/HCTZ 25 mg) once daily 1
- Maintenance dose: One capsule once or twice daily
- Maximum daily dose: Two capsules daily (total of triamterene 75 mg/HCTZ 50 mg)
- Administration: Take after meals to enhance absorption
For Edema:
- Initial dose: One capsule once daily
- Titration: May increase to one capsule twice daily if needed for adequate response
- Maximum daily dose: Two capsules daily
Clinical Considerations
Efficacy
- Dyazide is effective for mild to moderate hypertension as monotherapy or as part of combination therapy 2, 3
- Studies show that the combination provides effective blood pressure reduction with both systolic and diastolic improvements 4
- The combination is particularly useful when potassium conservation is desired alongside diuretic effects
Bioavailability Considerations
- It's important to note that Dyazide has lower bioavailability compared to some other formulations of triamterene/hydrochlorothiazide (like Maxzide) 2, 5
- Two Dyazide capsules deliver approximately half the quantity of both hydrochlorothiazide and triamterene as one Maxzide tablet (75 mg triamterene/50 mg hydrochlorothiazide) 2
Patient Selection
Dyazide is particularly beneficial for:
- Patients at risk for hypokalemia on thiazide diuretics alone
- Elderly patients who may be more susceptible to electrolyte disturbances
- Patients with hypertension who cannot tolerate potassium supplements
- Patients with mild edema requiring diuretic therapy
Monitoring and Safety
Required Monitoring:
- Serum electrolytes (particularly potassium) within 4 weeks of initiating therapy and periodically thereafter 6
- Renal function (BUN, creatinine)
- Blood pressure response
- Signs of fluid/electrolyte imbalance
Contraindications:
- Hyperkalemia
- Severe renal impairment (eGFR <30 mL/min/1.73m²)
- Anuria
- Concurrent use with other potassium-sparing diuretics
- Concurrent use with potassium supplements unless under close medical supervision
Precautions:
- Risk of hyperkalemia is increased when combined with ACE inhibitors or ARBs 7
- Avoid in patients with significant renal dysfunction
- All potassium supplementation should be discontinued when starting Dyazide 8
Special Populations
Elderly:
- Start at lower doses and monitor more closely
- Clearance of both components decreases with age 5
Renal Impairment:
- For moderate-to-severe CKD (eGFR <30 mL/min), loop diuretics are generally preferred over thiazide-containing products 6
- Triamterene should be used with caution in patients with reduced renal function due to risk of hyperkalemia
Hepatic Impairment:
- Use with caution; may require dose reduction
By following these recommendations, Dyazide can be effectively and safely used to manage hypertension and edema while minimizing the risk of hypokalemia associated with thiazide diuretic monotherapy.