Drug Information: Losartan
Detailed information regarding Losartan, a medication commonly used in clinical settings. Losartan belongs to a class of drugs known as angiotensin II receptor blockers (ARBs). It works by blocking the action of angiotensin II, a substance in the body that causes blood vessels to tighten. By blocking angiotensin II, Losartan helps blood vessels relax and widen, which lowers blood pressure. It is also used to protect the kidneys in patients with diabetes and to reduce the risk of stroke in patients with high blood pressure and an enlarged heart.
Category
Antihypertensive
Mechanism of Action
Losartan is an Angiotensin II Receptor Blocker (ARB). Angiotensin II is a potent vasoconstrictor and plays a key role in the renin-angiotensin-aldosterone system (RAAS), which regulates blood pressure and fluid balance. Losartan selectively blocks the AT1 receptor subtype, one of the two major angiotensin II receptor subtypes. By blocking the AT1 receptor, Losartan prevents angiotensin II from binding and exerting its effects. This leads to:
- Vasodilation: Blood vessels relax and widen, reducing peripheral resistance and blood pressure.
- Reduced Aldosterone Release: Lower levels of aldosterone, a hormone that promotes sodium and water retention, leading to decreased blood volume.
- Decreased Sodium Reabsorption: The kidneys excrete more sodium and water, further reducing blood volume and pressure.
- Cardiac Remodeling Prevention: Long-term angiotensin II blockade can help prevent or reverse cardiac hypertrophy (enlargement) and fibrosis (scarring) in the heart.
Unlike ACE inhibitors, ARBs like Losartan do not inhibit the breakdown of bradykinin, another substance involved in blood pressure regulation. This difference may contribute to a lower incidence of cough compared to ACE inhibitors.
Clinical Uses
Losartan is primarily used in the treatment of:
- Hypertension: As an antihypertensive, Losartan helps lower blood pressure, reducing the risk of stroke, heart attack, and kidney problems. It is often used as a first-line treatment or in combination with other antihypertensive medications.
- Diabetic Nephropathy: Losartan protects the kidneys from damage in patients with type 2 diabetes and proteinuria. It slows the progression of kidney disease by reducing protein leakage into the urine.
- Heart Failure: Losartan can be used to treat heart failure, especially in patients who cannot tolerate ACE inhibitors. It improves symptoms and reduces the risk of hospitalization and death.
- Stroke Prevention: In patients with hypertension and left ventricular hypertrophy, Losartan reduces the risk of stroke compared to other antihypertensive medications.
- Off-label Uses: It may also be used off-label for migraine prophylaxis and Raynaud’s phenomenon.
Dosage
Adults:
- Hypertension: The usual starting dose is 50 mg once daily. The dose may be increased to 100 mg once daily if needed to control blood pressure.
- Diabetic Nephropathy: The usual dose is 50 mg once daily, which may be increased to 100 mg once daily based on blood pressure response.
- Heart Failure: The usual starting dose is 12.5 mg once daily, gradually increased to a target dose of 50 mg once daily, as tolerated.
Pediatric:
- Hypertension (6 years and older): The usual starting dose is 0.7 mg/kg once daily (up to 50 mg total). The dose may be adjusted based on blood pressure response. Maximum dose is 50 mg daily.
Route of Administration: Oral. Losartan can be taken with or without food.
Indications
Common indications for Losartan include:
- Hypertension (high blood pressure)
- Diabetic nephropathy in patients with type 2 diabetes
- Reduction of stroke risk in hypertensive patients with left ventricular hypertrophy
- Heart failure
Contraindications
Losartan is contraindicated in:
- Patients with known hypersensitivity to Losartan or any of its components.
- Pregnancy (especially during the second and third trimesters) – can cause fetal injury or death.
- Concomitant use with aliskiren in patients with diabetes.
Caution should be exercised in patients with volume depletion, renal artery stenosis, or severe renal impairment.
FAQ
- Q: What is Losartan used for?
A: Losartan is primarily used to treat high blood pressure (hypertension), protect the kidneys in patients with diabetes, and reduce the risk of stroke in patients with high blood pressure and an enlarged heart. - Q: How does Losartan work?
A: Losartan blocks the action of angiotensin II, a substance in the body that causes blood vessels to tighten. By blocking angiotensin II, Losartan helps blood vessels relax and widen, which lowers blood pressure. - Q: What are the common side effects of Losartan?
A: Common side effects may include dizziness, lightheadedness, and nasal congestion. Less common but more serious side effects can include allergic reactions and kidney problems. - Q: Can I take Losartan if I am pregnant?
A: No, Losartan is contraindicated in pregnancy, especially during the second and third trimesters, as it can cause fetal injury or death. - Q: Can I drink alcohol while taking Losartan?
A: It’s best to avoid or limit alcohol consumption while taking Losartan, as alcohol can lower blood pressure and may increase the risk of dizziness or lightheadedness. - Q: What should I do if I miss a dose of Losartan?
A: If you miss a dose, take it as soon as you remember. However, if it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not double the dose to catch up. - Q: Can Losartan be taken with other medications?
A: Losartan can interact with other medications, including other blood pressure medications, NSAIDs (like ibuprofen), and potassium supplements. It’s important to inform your doctor about all medications you are taking. - Q: How long does it take for Losartan to start working?
A: Losartan typically starts to lower blood pressure within a few hours, but it may take several weeks to see the full effect. It’s important to continue taking the medication as prescribed, even if you don’t feel any different.
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