1. Clinical Overview
A triple-drug, fixed-dose combination (FDC) antihypertensive therapy containing an angiotensin II receptor blocker (ARB), a dihydropyridine calcium channel blocker (CCB), and a thiazide diuretic. This combination provides synergistic blood pressure lowering through complementary mechanisms, targeting the renin-angiotensin-aldosterone system (RAAS), vascular smooth muscle calcium channels, and sodium/fluid balance. It is indicated for patients whose hypertension is not adequately controlled on dual therapy. The FDC improves compliance by reducing pill burden.
| Onset | Duration | Bioavailability |
|---|---|---|
| Amlodipine: 30-60 minutes; Hydrochlorothiazide: 2 hours; Losartan: 1 hour (antihypertensive effect), peak effect in 6 hours. | Amlodipine: >24 hours; Hydrochlorothiazide: 6-12 hours; Losartan: >24 hours. The combination provides sustained 24-hour coverage. | Losartan: ~33%; Amlodipine: 64-90%; Hydrochlorothiazide: ~70%. |
2. Mechanism of Action
The combination exerts a multi-pronged attack on hypertension. Losartan selectively and competitively antagonizes the AT1 receptor, blocking the vasoconstrictor and aldosterone-secreting effects of angiotensin II. Amlodipine inhibits the transmembrane influx of calcium ions into vascular smooth muscle and cardiac muscle, causing peripheral arterial vasodilation and reduced peripheral vascular resistance. Hydrochlorothiazide inhibits sodium reabsorption in the distal convoluted tubule of the nephron, increasing excretion of sodium, chloride, and water, thereby reducing plasma volume.
3. Indications & Uses
- Essential Hypertension (uncontrolled on dual therapy with any two of the component classes)
4. Dosage & Administration
Adult Dosage: One tablet once daily. Dose may be titrated after 2-4 weeks based on response. Maximum: One tablet of this strength per day.
Administration: Can be taken with or without food. Administer at the same time each day, preferably in the morning to avoid nocturia from diuretic effect. Swallow whole with a glass of water. Do not crush or chew. Dose is not influenced by food.
5. Side Effects
Common side effects may include:
- Dizziness
- Headache
- Peripheral edema (mainly due to amlodipine)
- Flushing
- Fatigue
- Nausea
- Cough (less than ACE inhibitors)
- Orthostatic hypotension
- Hyperuricemia
- Hypokalemia (may be attenuated by losartan)
- Increased blood glucose
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Other Antihypertensives (Diuretics, Beta-blockers, ACEi) | Additive hypotensive effect. Risk of severe hypotension. | Major |
| NSAIDs (e.g., Ibuprofen, Diclofenac) | May reduce antihypertensive effect of losartan/HCTZ. Increase risk of renal impairment, especially in volume-depleted patients. | Major |
| Lithium | HCTZ reduces renal clearance of lithium, increasing risk of lithium toxicity. | Major |
| Potassium supplements / Potassium-sparing diuretics (Spironolactone, Amiloride) | Increased risk of hyperkalemia due to losartan. | Major |
| Digoxin | HCTZ-induced hypokalemia/hypomagnesemia may increase risk of digoxin toxicity. | Moderate |
| CYP3A4 Inhibitors (e.g., Ketoconazole, Itraconazole, Clarithromycin, Ritonavir) | May increase amlodipine levels, increasing risk of hypotension and edema. | Moderate |
| CYP3A4 Inducers (e.g., Rifampicin, Carbamazepine, Phenytoin) | May decrease amlodipine levels, reducing efficacy. | Moderate |
| Allopurinol | Increased risk of hypersensitivity reactions when combined with HCTZ. | Moderate |
| Antidiabetic drugs (Insulin, Sulfonylureas) | HCTZ may decrease glucose tolerance, requiring dose adjustment. | Moderate |
| Cholestyramine, Colestipol | May reduce absorption of HCTZ. Administer HCTZ at least 4 hours before these resins. | Moderate |
| Alcohol, Barbiturates, Narcotics | Potentiation of orthostatic hypotension. | Moderate |
7. Patient Counselling
- DO take the medicine at the same time every day, preferably in the morning.
- DO continue taking this medicine even if you feel well. Hypertension often has no symptoms.
- DO get your blood pressure, kidney function, and potassium levels checked regularly as advised by your doctor.
- DO inform all your doctors and dentists that you are taking this medicine before any surgery or new prescription.
- DONT stop taking this medicine suddenly without consulting your doctor.
- DONT take over-the-counter NSAIDs (like ibuprofen) for pain/fever without consulting your doctor.
- DONT use potassium supplements or salt substitutes containing potassium unless prescribed.
- DONT become dehydrated. Ensure adequate fluid intake, especially in hot weather or during illness with diarrhea/vomiting.
8. Toxicology & Storage
Overdose: Primary manifestation is likely to be profound hypotension and tachycardia. Other symptoms may include bradycardia, drowsiness, electrolyte disturbances (hypokalemia, hyponatremia), dehydration from diuretic effect, and acute renal failure.
Storage: Store below 30°C. Protect from light and moisture. Keep the tablet in the blister pack until use. Keep out of reach of children.