[4] Common adverse effects include muscle cramps, stuffy nose, dizziness, cough, high blood potassium, and anemia.

[13] Losartan is used for hypertension, including in people with left ventricular hypertrophy (enlarged heart muscle), and kidney dysfunction among type II diabetics.

[14] Although evidence shows calcium channel blockers and thiazide-type diuretics are preferred first-line treatments for most people (due to both efficacy and cost), an angiotensin II receptor antagonist such as losartan is recommended as first-line treatment in people under the age of 55 who cannot tolerate an ACE inhibitor.

[16] The most common adverse effects for losartan in adults are upper respiratory infections, dizziness, and back pain.

[3] In October 2014, the U.S. Food and Drug Administration (FDA) issued a black box warning that losartan can cause fetal toxicity and should be discontinued as soon as pregnancy is detected.

[19][3] Overdosing would most likely result in decreased blood pressure, which could manifest as an increased heart rate, dizziness, feeling lightheaded, or loss of consciousness.

[3] Losartan may have adverse interactions with phenobarbital, rifampin, or fluconazole, possibly inhibiting its blood pressure-lowering effects.

Losartan administration results in a decrease in total peripheral resistance (afterload) and cardiac venous return (preload).

As a result of losartan dosing, plasma renin activity increases due to the removal of the angiotensin II feedback.

[citation needed] Angiotensin II receptor antagonists include losartan, valsartan, azilsartan, candesartan, eprosartan, irbesartan, olmesartan, and telmisartan.

As a specific inhibitor of the urate transporter 1 (SLC22A12, URAT1), losartan blocks the uptake of uric acid into cells, thus leaving more available in the bloodstream to be filtered and excreted by the kidneys.

[41] Losartan is well absorbed following oral administration and undergoes significant first-pass metabolism to produce the 5-carboxylic acid metabolite, designated as EXP3174.

About 14% of an oral dosage is converted to this metabolite, which is long-acting (6 to 8 hours) and a noncompetitive antagonist at the AT1 receptor, contributing to the pharmacological effects of losartan.