Introduction
Dyazide is a combination antihypertensive/diuretic medication containing hydrochlorothiazide 25 mg and triamterene 37.5 mg. This fixed-dose combination product is commonly prescribed for the management of hypertension and edema associated with congestive heart failure, hepatic cirrhosis, and nephrotic syndrome. The combination provides complementary mechanisms of action while minimizing potassium depletion.
Mechanism of Action
Dyazide exerts its therapeutic effects through two distinct mechanisms:
Hydrochlorothiazide: Inhibits sodium chloride cotransport in the distal convoluted tubule, promoting excretion of sodium, chloride, and water. This results in reduced plasma volume and extracellular fluid volume. Triamterene: Acts as a potassium-sparing diuretic by blocking sodium channels in the cortical collecting duct, reducing potassium secretion and decreasing sodium reabsorption.The combination provides effective diuresis while mitigating the potassium-wasting effects of thiazide diuretics.
Indications
- Hypertension (as monotherapy or in combination with other antihypertensive agents)
- Edema associated with:
- Congestive heart failure - Hepatic cirrhosis - Nephrotic syndrome - Idiopathic edema
Dosage and Administration
Standard adult dosage: 1-2 capsules once daily or every other day Administration: Oral administration with food to minimize gastrointestinal upset Special populations:- Geriatric patients: Initiate with lower doses due to potential age-related renal impairment
- Renal impairment: Contraindicated in patients with severe renal impairment (CrCl <30 mL/min)
- Hepatic impairment: Use with caution; monitor for electrolyte imbalances
Pharmacokinetics
Absorption:- Hydrochlorothiazide: ~70% bioavailability
- Triamterene: Variable absorption (~30-70%)
- Both components extensively bound to plasma proteins
- Cross placental barrier and enter breast milk
- Hydrochlorothiazide: Not significantly metabolized
- Triamterene: Extensively metabolized via hydroxylation to active metabolite (hydroxytriamterene sulfate)
- Hydrochlorothiazide: Renal excretion (95%)
- Triamterene: Renal excretion (21%) and fecal elimination (metabolites)
- Half-life: Hydrochlorothiazide 5.6-14.8 hours; Triamterene 1.5-2.5 hours
Contraindications
- Anuria
- Severe renal impairment (CrCl <30 mL/min)
- Hyperkalemia
- Hypersensitivity to any component
- Concomitant use with potassium supplements or potassium-sparing agents
- Addison's disease
- Acute or chronic renal insufficiency
Warnings and Precautions
Hyperkalemia: Risk increased in patients with renal impairment, diabetes, elderly patients, and those taking ACE inhibitors, ARBs, or NSAIDs Electrolyte imbalances: Monitor for hyponatremia, hypochloremia, and hypomagnesemia Renal effects: May precipitate azotemia in patients with renal disease Hepatic effects: May cause hepatic encephalopathy in patients with severe liver disease Metabolic effects: May alter glucose tolerance and increase serum uric acid Photosensitivity: Both components may cause photosensitivity reactionsDrug Interactions
Significant interactions:- ACE inhibitors/ARBs: Increased risk of hyperkalemia
- NSAIDs: Reduced diuretic and antihypertensive effects; increased risk of renal impairment
- Lithium: Reduced lithium clearance leading to toxicity
- Digoxin: Triamterene may decrease renal clearance of digoxin
- Other antihypertensives: Additive hypotensive effects
- Cholestyramine/Colestipol: Reduced absorption of hydrochlorothiazide
Adverse Effects
Common (≥1%):- Dizziness
- Headache
- Dry mouth
- Gastrointestinal disturbances
- Electrolyte imbalances
- Photosensitivity
- Hyperkalemia (may be fatal)
- Acute renal failure
- Stevens-Johnson syndrome
- Pancreatitis
- Blood dyscrasias
- Hepatic toxicity
- Anaphylactic reactions
Monitoring Parameters
- Serum electrolytes (potassium, sodium, chloride) at baseline and periodically
- Renal function (BUN, creatinine)
- Blood pressure
- Body weight (for edema management)
- Complete blood count
- Uric acid levels
- Glucose levels (in diabetic patients)
- Signs of fluid/electrolyte imbalance
Patient Education
- Take with food to minimize stomach upset
- Report signs of electrolyte imbalance: muscle weakness, cramps, fatigue, irregular heartbeat
- Avoid excessive potassium-rich foods unless directed by healthcare provider
- Use sun protection due to photosensitivity risk
- Rise slowly from sitting/lying position to prevent dizziness
- Regular blood tests are necessary during treatment
- Inform all healthcare providers about Dyazide use
- Do not use potassium supplements unless specifically prescribed
- Report any signs of infection (sore throat, fever) promptly
References
1. Sica DA, Carter B, Cushman W, et al. Thiazide and loop diuretics. J Clin Hypertens. 2011;13(9):639-643.
2. Ellison DH. Diuretic therapy and resistance in congestive heart failure. Cardiology. 2001;96(3-4):132-143.
3. FDA Prescribing Information: Dyazide (hydrochlorothiazide and triamterene). Revised 2021.
4. Grossman E, Messerli FH. Drug-induced hypertension: an unappreciated cause of secondary hypertension. Am J Med. 2012;125(1):14-22.
5. Palmer BF. Metabolic complications associated with use of diuretics. Semin Nephrol. 2011;31(6):542-552.
6. Roush GC, Kaur R, Ernst ME. Diuretics: a review and update. J Cardiovasc Pharmacol Ther. 2014;19(1):5-13.
7. Weir MR, Rolfe M. Potassium homeostasis and renin-angiotensin-aldosterone system inhibitors. Clin J Am Soc Nephrol. 2010;5(3):531-548.
Note: This information is for educational purposes only and does not constitute medical advice. Patients should consult their healthcare provider for personalized medical recommendations.