Losartan: Uses, Interactions, Mechanism Of Action
Losartan is an AT1 antagonist, which is often used in treatment of high blood pressure and to decrease stroke risk associated with hypertension. It comes under a category of drugs given the name angiotensin II receptor blockers or more commonly ARBs. This is achieved through the inhibition of a hormone called renin reacting with angiotensinogen to produce angiotensin II, a hormone that causes blood vessels to contract and therefore, the blood pressure to rise.
USES
Hypertension : Losartan is very effective in the management of hypertension either as a monotherapy or in combination with other diuretic drugs. Reducing the blood pressure reduces the risk of such diseases as heart disease, stroke, and kidney related complications.
Diabetic Nephropathy: It is found that Losartan can delay the development of diabetic nephropathy. In this condition, diabetes causes renal impairment or chronic kidney disease. It can reduce the risk of chronic kidney disease in patients with type 2 diabetes as it reduces both blood pressure, and the amount of protein in urine, which is an early sign of kidney disease.
Heart Failure: Losartan can also be used to treat heart failure, particularly in patients who cannot tolerate ACE inhibitors due to their side effects. It helps improve the heart's ability to pump blood and reduce symptoms such as fatigue, shortness of breath, and fluid retention. Stroke Risk Reduction: In patients with hypertension and left ventricular hypertrophy, losartan helps lower the risk of stroke. This cardiovascular protection makes it an important component of therapy for high-risk patients.
Mechanism Of Action
Losartan works by blocking the effects of angiotensin II, a potent vasoconstrictor that narrows blood vessels and stimulates the release of aldosterone, This hormone causes the body to retain salt and water. Angiotensin II plays a central role in regulating blood pressure and fluid balance. Losartan exerts its effects by selectively inhibiting the binding of angiotensin II to the AT1 receptor.
Interaction
Diuretics: Losartan is often used in combination with diuretics, such as hydrochlorothiazide, to enhance blood pressure reduction. However, the use of other diuretics may increase potassium levels which can increase the risk of hyperkalaemia which can be dangerous.
ACE Inhibitors and Other ARBs: Combining losartan with other ACE inhibitors or ARBs is generally avoided, as this can increase the risk of renal dysfunction, hyperkalaemia, and hypotension without providing benefit to the patient. Patients taking these combinations need careful monitoring.
Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) : NSAIDs may reduce the antihypertensive effect of losartan by causing sodium and water retention. Furthermore, in patients with kidney disease or dehydration, the combination of NSAIDs and losartan can worsen kidney function, potentially leading to acute kidney injury.
Rifampin : Rifampin, an antibiotic used to treat tuberculosis, can reduce the effectiveness of losartan by increasing its metabolism, leading to lower plasma concentrations and a reduced antihypertensive effect.
Potassium Supplements and Salt Substitutes: Since losartan can increase potassium levels by reducing aldosterone activity, combining it with potassium supplements or salt substitutes containing potassium can increase the risk of hyperkalaemia. This can cause dangerous heart arrhythmias and other complications.
Side Effects
While losartan is generally well-tolerated, it can cause a range of side effects. Some of the most common and serious side effects include:
Hypotension: Losartan may cause a significant drop in blood pressure, especially in patients who are dehydrated or on high doses. Symptoms of hypotension include dizziness, light-headedness, and fainting.
Hyperkalaemia: By reducing aldosterone activity, losartan can increase potassium levels, potentially leading to hyperkalaemia, a condition that can cause irregular heartbeats, weakness, and cardiac arrest.
Kidney Impairment: Losartan can affect kidney function, especially in patients with existing kidney disease. Monitoring kidney function is important during treatment to avoid worsening renal impairment.
Fatigue and Dizziness: These are common side effects, especially when starting treatment or increasing the dose, due to the blood pressure-lowering effects.
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