Draft 1 High blood pressure is a condition where the blood pumped by the heart exerts high forces on the walls of arteries, which are the vessels by which blood flows from the heart to the body's organs, tissues, and cells. According to the American Heart Association, approximately 73 million adults in the United States have high blood pressure, which is also called hypertension (http://www.americanheart.org/). In 2004, more than 50,000 Americans died directly as a result of this disease. Hypertension is a major risk factor for heart attacks and strokes, which cause more than 500,000 deaths in the U.S. every year. Blood pressure is measured with a device called a sphygmomanometer, which consists of an inflatable arm cuff and a numbered dial that indicates pressure values in millimeters of mercury (mmHg). Blood pressure readings are expressed with two values. First, systolic pressure indicates how much force the blood exerts while the heart is contracting. Secondly, diastolic pressure indicates how much force is exerted while the heart is relaxing in between contractions. Normal values of blood pressure are slightly lower than 120 mmHg (systolic) and 80 mmHg (diastolic). High blood pressure is designated by measures exceeding 140 mmHg (systolic) and 90 mmHg (diastolic). One treatment for hypertension is a class of drugs called beta blockers. These drugs lower blood pressure by slowing heart rate and reducing the heart's force when beating. The force that the heart produces when it contracts is increased by a naturally occurring hormone called epinephrine, which is also called adrenaline. To affect the heart, this hormone must attach to receptor molecules, called beta receptors, which are located on cardiac cells. Beta blockers are drugs that block the beta receptors so that adrenaline cannot attach to them. Because the drugs block adrenaline, it does not have its normal effect of increasing heart rate and contractile force. Therefore blood pressure is reduced. High blood pressure can also be treated with another class of drugs, called angiotensin-converting enzyme inhibitors, or ACE inhibitors. These drugs work by relaxing and dilating the peripheral arteries throughout the body. ACE inhibitors block the formation of the hormone angiotensin-II, which naturally constricts the arteries. The drugs reduce blood pressure by relaxing and dilating the arteries. Doctors prescribe combinations of different medications to lower blood pressure in patients with hypertension. The purpose of this critical review paper is to present research that has been conducted on which combinations are most effective in lowering blood pressure without negative side effects. Draft 2 According to the American Heart Association, high blood pressure, which is also called hypertension, affects approximately 73 million adults in the United States (http://www.americanheart.org/). In 2004, more than 50,000 Americans died directly as a result of this disease. Hypertension is a major risk factor for heart attacks and strokes, which cause more than 500,000 deaths in the U.S. every year. The prognosis for patients with hypertension is good if they seek treatment. Johnson et al. (2) reported that in hypertensive patients who lowered their blood pressure with medication, risks of heart attack and stroke declined by 20 to 40%. However, pharmacological approaches to treating hypertension are not always effective, and many questions remain about the optimal drugs to prescribe for lowering blood pressure. A major reason that medications for hypertension are not always effective is that the causes of the disease are so complex. Over 50 medications are currently available for treating the disease. Each drug works on specific causes. For instance, drugs in a class called beta blockers reduce blood pressure by slowing the heart rate and reducing the heart's contractile force. Other groups of drugs influence the function of different organs and tissues. For instance, ACE inhibitors work by dilating peripheral blood vessels and reducing the resistance to blood flow. Diuretics lower the volume of blood in the body, reducing how much pressure the blood creates against the arteries when the heart contracts. One problem that doctors face is determining which anti-hypertension drug to prescribe. For instance, a beta blocker that lowers blood pressure in one patient may not work effectively in another patient, who might respond better to an ACE inhibitor. When doctors first diagnose hypertension they usually prescribe a single drug. This approach, which is called "monotherapy," is effective in lowering blood pressure to healthy levels in only 50 to 60% of cases (3). For individuals who do not respond optimally to monotherapy, doctors prescribe a combination of two to four drugs. This approach is called "combined drug therapy." While the combined approach has been reported to be effective, there are several unanswered questions about its use. A major question deals with which drugs to combine for the optimal effects of lowering blood pressure. Should a beta blocker be combined with an ACE inhibitor or a diuretic? Which drugs work optimally when combined with calcium-channel blockers? Also at issue is the optimal dose for each combined drug. Should the doses be kept at the same levels that are used for monotherapy? Or should the doses of each drug be lowered, and if so by how much? Finally, there are concerns about dangerous side effects of combining certain drugs. Research has been conducted to provide answers to these questions about optimal approaches to combined drug therapy for hypertension. In this paper I will critically review studies that have addressed optimal combinations, correct dosing, and negative side effects. Based on this review of the literature I will recommend certain drug combinations and doses for the best outcomes in hypertensive patients.