Antihypertensive drugs, also known as anti hypertension drugs, is a kind of medicine which can control blood pressure and be used for the treatment of hypertension. Antihypertensive drugs mainly take effects through influencing systems which play an important role in regulating blood pressure physiologically, such as the sympathetic nervous system, the renin-angiotensin-aldosterone system, the endothelin system and so on. There are five categories of common first-line antihypertensive drugs including diuretic drugs (Hydrochlorothiazide and Furosemide), beta blockers (such as Metoprolol), angiotensin-converting enzyme inhibitor (ACEI) (such as Captopril), angiotensin II receptor blockers (ARB), and calcium antagonists (CCB). The common effect of these antihypertensive drugs is to reduce blood pressure, but because of differences of hypotensive mechanism, different kinds of antihypertensive drugs have their emphasis which doctors depend on to choose antihypertensive drugs for different patients. When hypertension is not serious, start treatment with a small dose of a drug, which can not only help to know a patient's reaction to the efficacy and tolerability of a drug but reduce the untoward effect to the lowest. If a small dose is not effective, increase dosage or change another drug (especially for elderly patients, reducing blood pressure should be slow). If the blood pressure is still out of control, combination treatment of various drugs should be considered.