The main differences between losartan (Cozaar) and valsartan (Diovan) are:

• Losartan has a shorter duration of action (length of time it works for) at lower dosages than valsartan. Research¹ indicates losartan lasts less than 24 hours at dosages of 25mg a day and 50mg a day. This may cause your blood pressure to rise at night if you take your dose in the morning. Dosages of 100mg per day or more of losartan will last for 24 hours. All dosages of valsartan last at least 24 hours. Talk to your doctor about this if you are prescribed a low dose of losartan
• There are some differences in what each drug is approved for. Losartan is FDA approved for high blood pressure, reducing the risk of stroke in patients with hypertension, left ventricular hypertrophy (an overdeveloped heart muscle), treating people with type 2 diabetes, and for hypertensive patients with diabetic nephropathy (kidney disease). Valsartan is FDA approved for high blood pressure and heart failure. It may also be given to reduce the risk of deaths in patients who have developed congestive heart failure after a heart attack
• Although the side effects of losartan and valsartan are similar, some side effects, such as chest pain, insomnia, low blood sugar (hypoglycemia), muscle cramps, a stuffy nose, urinary tract infections (UTIs) and weakness are reported more frequently with losartan. Other side effects, such as abdominal pain, cough, headache, and nausea, are reported more frequently with valsartan
• Losartan has been available for longer than valsartan (losartan was FDA approved in 1995, valsartan was FDA approved in 1996)
• Valsartan is available in combination with sacubitril, a neprilysin inhibitor. The combination is called Entresto. Losartan is not available in combination with sacubitril.

There are also many similarities between losartan and valsartan, for example:

• Both belong to the same class of medicine, called ARBs (angiotensin receptor blockers). They work by blocking a substance called angiotensin II that causes blood vessels to narrow (constrict). Blocking this substance means blood vessels can widen (dilate), which lowers blood pressure
• Both are used to treat high blood pressure
• Side effects that are common to both losartan and valsartan include diarrhea, dizziness, and fatigue
• Both are available as cheap generics, so cost should be similar
• Research has shown that both losartan and valsartan (and all other ARBs) are beneficial at controlling blood pressure, slowing the progression of kidney disease in people with diabetes (diabetic nephropathy), and decreasing the risk of stroke in patients with left ventricular hypertrophy
• Both losartan and valsartan can increase levels of potassium in your blood, which means you may require regular blood tests to monitor for this
• Both are available as a combination pill with the diuretic hydrochlorothiazide (Losartan/HCTZ and valsartan/HCTZ). Both drugs work together to lower blood pressure, and the combination may cause fewer potassium abnormalities because hydrochlorothiazide lowers potassium while losartan/valsartan raises it
• Both may interact with lithium, other blood pressure medications, potassium-sparing diuretics, potassium supplements, salt substitutes containing potassium, nonsteroidal anti-inflammatory drugs (NSAIDs: example ibuprofen [Advil, Motrin], naproxen [Aleve], celecoxib, or diclofenac).
• Neither losartan nor valsartan should be used during pregnancy and they are not recommended during breastfeeding.

1. Nishimura T, Hashimoto J, Ohkubo T, et al. Efficacy and Duration of Action of the Four Selective Angiotensin II Subtype 1 Receptor Blockers, Losartan, Candesartan, Valsartan and Telmisartan, in Patients with Essential Hypertension Determined by Home Blood Pressure Measurements. Clinical and Experimental Hypertension 2005:27;6:477-89. DOI: 10.1081/CEH-200067668