1. Clinical Overview
A fixed-dose combination (FDC) antihypertensive agent containing an ACE inhibitor (Ramipril) and a thiazide diuretic (Hydrochlorothiazide). This combination provides synergistic blood pressure lowering through complementary mechanisms, often allowing for lower doses of each component, thereby improving efficacy and potentially reducing side effects. It is a mainstay in the management of essential hypertension in the Indian population, where combination therapy is frequently required to achieve target BP goals.
| Onset | Duration | Bioavailability |
|---|---|---|
| Ramipril: 1-2 hours; Hydrochlorothiazide: Diuresis begins within 2 hours, peak antihypertensive effect in 4-6 weeks. | Ramipril: 24 hours; Hydrochlorothiazide: 6-12 hours (diuretic), 24+ hours (antihypertensive). | Ramipril: 50-60% (as Ramiprilat); 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 increased bradykinin levels (contributing to vasodilation). Hydrochlorothiazide inhibits sodium-chloride symport in the distal convoluted tubule of the nephron, promoting excretion of sodium, chloride, and water. The combination results in additive reduction of peripheral vascular resistance and plasma volume.
3. Indications & Uses
- Essential Hypertension (Stage 1 & 2) where combination therapy is appropriate
4. Dosage & Administration
Adult Dosage: One tablet (Ramipril 2.5mg + HCTZ 12.5mg) once daily. Dose may be titrated up to a maximum of Ramipril 10mg + HCTZ 25mg daily, based on therapeutic response. Usually taken in the morning.
Administration: Administer orally, with or without food. Swallow whole with a glass of water. Consistent timing daily is recommended. Avoid taking in the evening to prevent nocturia. If a dose is missed, take it as soon as remembered unless it's almost time for the next dose. Do not double the dose.
5. Side Effects
Common side effects may include:
- Dizziness, lightheadedness (especially with initial doses)
- Persistent dry cough (Ramipril)
- Headache
- Fatigue
- Orthostatic hypotension
- Hyperglycemia
- Increased serum uric acid
- Hypokalemia (HCTZ) or Hyperkalemia (Ramipril - less common)
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Potassium supplements / Potassium-sparing diuretics (Spironolactone, Amiloride) | Increased risk of severe hyperkalemia. | Major |
| Non-Steroidal Anti-Inflammatory Drugs (NSAIDs: Ibuprofen, Diclofenac) | May reduce antihypertensive effect and increase risk of renal impairment. | Major |
| Lithium | HCTZ reduces renal clearance of Lithium, leading to toxicity. | Major |
| Other Antihypertensives (Beta-blockers, Calcium channel blockers) | Additive hypotensive effect. | Moderate |
| Antidiabetic drugs (Insulin, Sulfonylureas) | HCTZ may decrease glucose tolerance, requiring dose adjustment. | Moderate |
| Allopurinol | Increased risk of hypersensitivity reactions. | Moderate |
| Cholestyramine / Colestipol | May reduce absorption of HCTZ. | Moderate |
| Alcohol, Barbiturates, Narcotics | Potentiation of orthostatic hypotension. | Moderate |
7. Patient Counselling
- DO take your medicine at the same time each day, usually in the morning.
- DO continue taking this medicine even if you feel well. Hypertension often has no symptoms.
- DO get up slowly from a sitting or lying position to avoid dizziness.
- DO inform all your doctors and dentists that you are taking this medicine.
- DONT stop taking this medicine suddenly without consulting your doctor.
- DONT use potassium supplements or salt substitutes containing potassium unless advised by your doctor.
- DONT take over-the-counter NSAIDs (like Ibuprofen) for pain/fever without consulting your doctor.
- DONT become dehydrated. Ensure adequate fluid intake, especially in hot weather or during illness with diarrhea/vomiting.
8. Toxicology & Storage
Overdose: Manifestations primarily related to excessive pharmacological effects: Severe hypotension, shock, bradycardia, electrolyte disturbances (hypokalemia or hyperkalemia, hyponatremia), dehydration, renal failure, lethargy, coma. Symptoms may be delayed due to Ramipril's prodrug nature.
Storage: Store below 30°C. Protect from light and moisture. Keep in the original blister pack or container. Keep out of reach of children. Do not use after the expiry date printed on the pack.