Olsertain-H-20 Tablet is a combination antihypertensive medication containing Olmesartan Medoxomil 20 mg and Hydrochlorothiazide 12.5 mg. Olmesartan Medoxomil is an angiotensin II receptor antagonist that selectively blocks the binding of angiotensin II to the AT1 receptor, thereby inhibiting vasoconstriction and aldosterone secretion, which results in vasodilation and reduction of blood pressure. Hydrochlorothiazide is a thiazide diuretic that promotes the excretion of sodium and water by inhibiting sodium reabsorption in the distal convoluted tubules of the kidneys, contributing to decreased blood volume and peripheral resistance. The combination of these two agents provides complementary mechanisms to effectively manage hypertension, especially in patients inadequately controlled by monotherapy. Olsertain-H-20 is indicated for the treatment of essential hypertension to reduce the risk of cardiovascular events such as stroke and myocardial infarction. It is important to monitor electrolyte levels, renal function, and blood pressure regularly during therapy. Contraindications include hypersensitivity to any component, anuria, and severe renal impairment. Caution is advised in patients with hepatic dysfunction, electrolyte imbalance, and volume depletion. This combination therapy should be used under medical supervision with appropriate dose adjustments based on clinical response.