The type of medication prescribed to treat high blood pressure  will depend upon the patient and any other underlying illnesses that they might have. Medications that are often used include:

• Diuretics: Often called "water pills," they cause the kidneys to make more urine and decrease the amount of fluid in the body.
  
  
• Beta blockers: These medications are named because they block the beta adrenaline receptors in the heart and blood vessels. They tend to relax the smooth muscles in artery walls decreasing the resting diastolic pressure. Additionally, they cause the heart to beat less forcefully, decreasing systolic pressure.
  
  
• Calcium channel blockers: These drugs work at the heart cell level, blocking the flow of calcium in and out of the cell, which causes the heart to contract less forcefully, and decreasing the systolic pressure it generates.
  
  
• Angiotensin receptor blockers (ARBs): These medications affect a group of hormones in the body that are associated with the kidney and blood pressure control, including renin, angiotensin, vasopressin and aldosterone. These medications cause arterial dilation and also affect the secretion of vasopressin and aldosterone.

Most patients with high blood pressure have primary or essential hypertension (high blood pressure for no specific reason). However, approximately 5% to 10% of patients may have secondary hypertension (high blood pressure due to an underlying cause or disease). These may include kidney or adrenal gland abnormalities, fibromuscular hyperplasia of an artery to the kidney, or side effects from medications or drugs. For that reason, it is wise that patients with high blood pressure readings seek care from a health professional.

References:

National Heart Lung and Blood Institute, National Institutes of Health, "The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure."

Rosendorff, C., Black, H., Cannon, C., Gersh, B., Gore, J., Izzo, J., Kaplan, N., O'Connor, C., O'Gara, P., Oparil, S.; "Treatment of Hypertension in the Prevention and Management of Ischemic Heart Disease." Circulation. 2007;115:2761-2788