1. Clinical Overview
A fixed-dose combination (FDC) antihypertensive medication containing an ACE inhibitor (Ramipril) and a thiazide diuretic (Hydrochlorothiazide). It provides synergistic blood pressure lowering by reducing angiotensin II formation and increasing sodium and water excretion. This combination is widely used in the Indian market for patients requiring more than one drug to achieve blood pressure control, improving compliance and offering cost-effectiveness.
| Onset | Duration | Bioavailability |
|---|---|---|
| Ramipril: 1-2 hours; Hydrochlorothiazide: Diuresis begins within 2 hours, peak effect at 4-6 hours. Antihypertensive effect of the combination is typically seen within 1-2 weeks. | Ramipril: 24 hours; Hydrochlorothiazide: 6-12 hours. The combination provides sustained 24-hour blood pressure control with once-daily dosing. | Ramipril: 50-60% (from prodrug ramipril); Hydrochlorothiazide: 50-80%. |
2. Mechanism of Action
Ramipril inhibits the angiotensin-converting enzyme (ACE), preventing the conversion of angiotensin I to the potent vasoconstrictor angiotensin II. This leads to vasodilation, reduced aldosterone secretion (decreasing sodium and water retention), and decreased bradykinin degradation. Hydrochlorothiazide inhibits the sodium-chloride symporter in the distal convoluted tubule of the nephron, promoting excretion of sodium, chloride, and water. The combination results in complementary mechanisms: reduced peripheral resistance (ramipril) and reduced plasma volume (HCTZ).
3. Indications & Uses
- Essential Hypertension (Stage 1 & 2) where combination therapy is appropriate
4. Dosage & Administration
Adult Dosage: One tablet (Ramipril 5mg + HCTZ 12.5mg) once daily. Dose may be titrated after 2-4 weeks based on response. Maximum: Ramipril 10mg + HCTZ 25mg per day (as per available FDC strengths).
Administration: Take orally once daily, preferably in the morning to avoid nocturia. Can be taken with or without food, but consistency is advised. Swallow whole with a glass of water. Ensure adequate hydration but avoid excessive fluid intake.
5. Side Effects
Common side effects may include:
- Persistent dry cough (ramipril)
- Dizziness, lightheadedness (especially with initial doses)
- Headache
- Fatigue
- Nausea
- Hyperkalemia (ramipril) OR Hypokalemia (HCTZ) - net effect variable
- Increased blood urea/creatinine
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Potassium supplements / Potassium-sparing diuretics (Spironolactone, Amiloride) | Increased risk of severe hyperkalemia | Major |
| NSAIDs (e.g., Ibuprofen, Diclofenac) | Reduced antihypertensive effect; increased risk of renal impairment | Major |
| Lithium | Increased lithium levels and toxicity (HCTZ reduces renal clearance) | Major |
| Antidiabetic drugs (Insulin, Sulfonylureas) | HCTZ may decrease glucose tolerance, requiring dose adjustment | Moderate |
| Other antihypertensives / Vasodilators | Additive hypotensive effect | Moderate |
| Allopurinol | Increased risk of hypersensitivity reactions | Moderate |
| Cholestyramine / Colestipol | Reduced absorption of HCTZ | Moderate |
| Corticosteroids | Enhanced hypokalemic effect (HCTZ) | Moderate |
| Alcohol | Potentiation of orthostatic hypotension | Moderate |
7. Patient Counselling
- DO take your medicine at the same time each day.
- DO get your blood pressure, kidney function (creatinine), and potassium levels checked regularly as advised.
- DO inform all your doctors and dentists you are on this medicine.
- DO maintain adequate fluid intake unless advised otherwise.
- DONT stop taking the medicine suddenly; consult your doctor.
- DONT take over-the-counter NSAIDs (e.g., ibuprofen) for pain/fever without consulting your doctor.
- DONT use potassium supplements or salt substitutes without medical advice.
- DONT become pregnant while on this medication.
8. Toxicology & Storage
Overdose: Manifestations primarily due to pharmacologic effects: Severe hypotension, shock, bradycardia, electrolyte disturbances (hypokalemia or hyperkalemia, hyponatremia), dehydration, renal failure, lethargy, coma. Symptoms may be delayed with ramipril.
Storage: Store below 30°C. Protect from light and moisture. Keep in the original blister pack or container. Keep out of reach of children.