Losartan is a medication prescribed to manage high blood pressure (hypertension). It lowers blood pressure and reduces stroke risk in some individuals. It also protects kidney function, especially in people with diabetes and high blood pressure. This article explores how Losartan works and its specific benefits for kidney health.
How Losartan Works
Losartan is an angiotensin receptor blocker (ARB). It targets the renin-angiotensin-aldosterone system (RAAS), a complex body system that regulates blood pressure. Angiotensin II, a hormone in this system, narrows blood vessels and stimulates aldosterone release, leading to sodium and water retention.
Losartan blocks the AT1 receptor, the primary binding site for angiotensin II in tissues like blood vessels and the adrenal glands. By preventing angiotensin II from binding, Losartan stops its effects, leading to vasodilation (the relaxation and widening of blood vessels). This reduces blood flow resistance, lowering blood pressure. The blockade also reduces aldosterone secretion, further lowering blood pressure by decreasing sodium and water retention.
Losartan and Kidney Protection
Losartan offers specific benefits for kidney health beyond simply lowering blood pressure. Angiotensin II can also cause harmful changes within the kidneys, particularly in conditions like diabetic kidney disease. By blocking the AT1 receptor, Losartan mitigates these detrimental effects.
Losartan protects the kidneys by reducing intraglomerular pressure. The glomeruli are tiny filtering units within the kidneys; high pressure can damage them and impair filtering. Losartan eases this pressure, preserving filter integrity.
It also decreases proteinuria (excess protein in the urine), a common sign of kidney damage, especially in patients with diabetes. Reducing proteinuria slows the progression of kidney disease. Clinical studies, such as the RENAAL trial, have shown that Losartan can significantly reduce the risk of kidney disease progression, including the doubling of serum creatinine levels and the need for dialysis in patients with type 2 diabetes and kidney disease. This highlights its long-term benefits for preserving kidney function.
Dosage, Administration, and Side Effects
Losartan is taken once daily, with or without food. For adults, the usual starting dose for high blood pressure is 50 mg once daily. The dose can be increased up to a maximum of 100 mg once daily, depending on blood pressure response. For patients with low fluid volume, such as those taking diuretics, a lower starting dose of 25 mg once daily may be recommended to prevent a sudden drop in blood pressure. Consistent adherence to the prescribed dosage is important for effectiveness.
Losartan can cause side effects. Common side effects include dizziness, particularly when standing up quickly. A more serious, but less common, side effect is hyperkalemia (elevated potassium in the blood). This is more likely if Losartan is taken with other medications that also increase potassium.
Changes in kidney function, including acute kidney failure, can occur, and regular monitoring by a healthcare professional is important. Angioedema (swelling of the face, lips, tongue, or throat) is a rare but serious side effect that requires immediate medical attention. It is important to discuss any concerns or side effects with a healthcare provider.
Losartan Compared to Other Medications
Losartan, an angiotensin receptor blocker (ARB), is often compared to angiotensin-converting enzyme (ACE) inhibitors, another class of medications used to treat high blood pressure and protect kidneys. Both act on the renin-angiotensin-aldosterone system to lower blood pressure and provide kidney protection. A key difference lies in their side effect profiles.
ACE inhibitors can cause a persistent dry cough in 5-35% of patients. This cough is due to the accumulation of bradykinin, a substance that ACE inhibitors prevent from breaking down. Losartan and other ARBs do not affect bradykinin metabolism in the same way, resulting in a much lower incidence of cough (typically less than 1%), often similar to a placebo. Therefore, Losartan may be preferred for patients who develop a cough while taking an ACE inhibitor, offering similar cardiovascular and kidney benefits without this side effect.