Losartan is a medication mainly used to treat high blood pressure. It is also used for diabetic kidney disease, heart failure, and left ventricular enlargement. It is taken by mouth. It may be used alone or in addition to other blood pressure medication. Up to six weeks may be required for the full effects to occur. 
Hydrochlorothiazide (HCTZ or HCT) is a diuretic medication often used to treat high blood pressure and swelling due to fluid build up. Other uses include treating diabetes insipidus and renal tubular acidosis and to decrease the risk of kidney stones in those with a high calcium level in the urine. For high blood pressure it is sometimes considered as a first-line treatment. HCTZ is taken by mouth and may be combined with other blood pressure medications as a single pill to increase effectiveness.