Co-Tasmi is a medication that contains two active ingredients, namely Telmisartan (40mg) and Hydrochlorothiazide (12.5mg). It is used to treat hypertension (high blood pressure) in patients who do not respond to treatment with one medication alone. Telmisartan is an angiotensin II receptor antagonist that works by blocking the action of a hormone that constricts blood vessels, thereby relaxing and widening the blood vessels and reducing blood pressure. Hydrochlorothiazide is a diuretic that helps to eliminate excess salt and water from the body, which also helps to lower blood pressure.