Blood pressure refers to the pressure of the blood on the blood vessel wall during its flow. Hypertension refers to that the arterial blood pressure (represented by the elbow brachial artery pressure) is higher than normal value. Owing to the different levels of health care in various countries and regions of the world, the decided hypertension range is also different. The standards in our country are: In the absence of administration of antihypertensive drugs, upon the case of systolic blood pressure being ≥140 mm Hg (18.6 × 103 Pa) or the diastolic blood pressure of ≥90 mm Hg (12.0 × 103 Pa), the patients should be deemed (or diagnosed) to get hypertension.

Clinically hypertension can be divided into two categories, one is the hypertension with unknown etiology, called "essential hypertension", also known as "hypertension disease"; the other one is the hypertension of clear cause such as hypertension caused by nephritis, brain tumors and other diseases with high blood pressure being only a symptom of these diseases, thus being called "secondary hypertension", also known as "symptomatic hypertension." What will be introduced here is mainly the former, namely hypertension. In Chinese medicine, it is classified into "Vertigo", "headache" category.

Antihypertensive drugs are drugs for the treatment of hypertension. It is also known as hypotensor. Rational application of antihypertensive drugs can not only make high blood pressure under control but can also reduce or eliminate the subjective symptoms caused by hypertension. Long-term administration can also reduce the complications of hypertension, such as stroke, cerebral infarction, myocardial infarction, heart failure and renal insufficiency, thus extending the life of the patient. Currently, there are over 350 kinds of anti-hypertension drug in total developed all around the world. But only over 100 species are available for the clinical application, of which 10 kinds have been respectively recommended by WHO (1985) and the National High Blood Pressure Education Commission (1988) to be used commonly anti-hypertensive drugs. Antihypertensive drugs, according to different mechanism of action, can be divided into diuretics, sympathetic blockers, vasodilators, calcium antagonists and angiotensin converting enzyme inhibitors five categories. In recent years, it has been also developed of potassium channel openers and serotonin type II receptor antagonists as novel anti-hypertensive drugs available with some of them still being under study and some having entered clinical trial stage. Different types of anti-hypertensive drugs, because of the different principles of action, have quite differences on the impact on hemodynamics, pharmacological effects and clinical applications (see the relevant terms).
However, an excellent anti-hypertensive drug should have the following properties: excellent gastrointestinal absorption, significant and long-lasting antihypertensive effect, not causing orthostatic hypotension and reflex tachycardia after medication, having no significant adverse reactions and toxicity, not causing blood renin activity, having no sodium retention, non-resistance, and having compatibility with other drugs. So far there have been yet no kinds of anti-hypertensive drugs that can meet all these requirements. Clinicians can properly select them according to the specific characteristics of the drug and the patient's exact conditions. In case of consideration of combination therapy, we refer to their similarities and differences, taking advantage of each other while reducing the adverse effects and enhancing the efficacy.