Zaart-H tablets contains losartan 50 mg and hydrochlorothiazide 12.5 mg which are used in the treatment of high blood pressure. Losartan is an angiotensin receptor blocker (ARB). It works by blocking the hormone angiotensin thereby relaxing blood vessels. This allows the blood to flow more smoothly and the heart to pump more efficiently. Hydrochlorothiazide is a diuretic that removes extra water and certain electrolytes from the body. Over time it also relaxes blood vessels and improves blood flow.