A drug used to lower excessively high blood pressure. The term hypertension denotes blood pressure above the normal range. It does not refer to excessive nervous or emotional tension. The term antihypertensive is sometimes used erroneously as if it had the same meaning as antianxiety (or tranquilizing) drug action.

Today there are more than 100 drug products in use for treating hypertension. Those most frequently prescribed for long-term use fall into three major groups:

Regardless of their mode of action, all these drugs share an ability to lower the blood pressure. It is important to remember that many other drugs can interact with antihypertensive drugs: some add to their effect and cause excessive reduction in blood pressure; others interfere with their action and reduce their effectiveness. Anyone who is taking medications for hypertension should consult with his or her physician whenever drugs are prescribed for the treatment of other conditions as well.

--From The Essential Guide to Prescription Drugs