Definition

Alpha₁-adrenergic blockers are drugs that work by relaxing the blood vessels, allowing blood to pass through more easily.

Purpose

These drugs, called alpha blockers for short, are used for two main purposes: to treat high blood pressure (hypertension) and to treat benign prostatic hyperplasia (BPH), a condition in men in which the prostate gland enlarges.

High blood pressure

High blood pressure puts a strain on the heart and the arteries. Over time, hypertension can damage the blood vessels enough to cause stroke, heart failure or kidney failure. People with high blood pressure also may be at higher risk for heart attacks. Controlling high blood pressure makes these problems less likely. By relaxing the blood vessels and letting blood flow through more easily, alpha blockers help lower blood pressure.

Benign prostatic hyperplasia

This condition is a particular problem for older men. Over time, the prostate, a donut-shaped gland below the bladder, enlarges. When this happens, it may interfere with the passage of urine from the bladder out of the body. Men who have the problem may notice that they have to urinate more often. Or they may feel that they can not completely empty their bladders. Alpha blockers do not shrink the prostate. But by relaxing muscles in the prostate and the bladder, these drugs may allow urine to flow more freely.

Description

Commonly prescribed alpha blockers include doxazosin (Cardura) and terazosin (Hytrin). Both are available only with a physician's prescription and are sold in tablet form.

Recommended dosage

The recommended dose depends on the patient and the type of alpha blocker and may change over the course of treatment. The physician who prescribed the medicine will gradually increase the dosage, if necessary. Some people may need as much as 15-20 mg per day, but most people benefit from lower doses. As the dose increases, so does the possibility of unwanted side effects.

Always take alpha blockers exactly as directed, even if the medicine does not seem to be working at first. Do not stop taking the medicine when symptoms improve. This type of medicine needs to be taken regularly to be effective. Try not to miss any doses, but never take larger or more frequent doses to make up for missed doses.

Precautions

Alpha blockers may make blood pressure drop too low. This can cause dizziness, lightheadedness, heart palpitations, and fainting. Avoid driving, using machines, or doing anything else that might be dangerous for 24 hours after taking the first dose. Be especially careful not to fall if getting up in the middle of the night. Take the same precautions if the dosage has been increased or if the drug has been stopped and then started again. Anyone whose safety on the job could be affected by taking alpha blockers should make sure his or her physician knows about this. The physician should then be careful about increasing dosage gradually.

Dizziness, lightheadedness, and fainting are more likely when people taking these drugs drink alcohol, exercise, stand for a long time, or are exposed to hot weather. Use extra care under these conditions and limit alcohol consumption while taking this medicine.

Some people feel drowsy or less alert when using these drugs. For those people, driving or doing dangerous that demands full attention is not recommended.

People with kidney disease or liver disease may be more sensitive to alpha blockers. They should be sure to let their physicians know about these problems if alpha blockers are prescribed. Older people may also be more sensitive to these drugs and may be more likely to have unwanted side effects, such as fainting, dizziness, and lightheadedness.

Remember that alpha blockers do not cure high blood pressure. They simply help keep the problem under control. Similarly, these drugs will not shrink an enlarged prostate gland. Although they will help relieve the symptoms of prostate enlargement, the prostate may continue to grow, and it eventually may be necessary to have prostate surgery.

Alpha blockers may lower blood counts. Patients may need to have their blood checked regularly while taking this medicine.

Anyone who has had unusual reactions to alpha blockers in the past should let his or her physician know before taking the drugs again. The physician should also be told about any allergies to foods, dyes, preservatives, or other substances.

The effects of taking alpha blockers during pregnancy are not fully known. Women who are pregnant or planning to become pregnant should let their physicians know. Breast-feeding mothers who need to take alpha blockers should also talk to their physicians. These drugs can pass into breast milk and may affect nursing babies. It may be necessary to stop breast-feeding while being treated with alpha blockers.

Side effects

The most common side effects are dizziness, drowsiness, tiredness, headache, nervousness, irritability, stuffy or runny nose, nausea, pain in the arms and legs, and weakness. These problems usually go away as the body adjusts to the drug and do not require medical treatment. If they do not go away or if they interfere with normal activities, check with the physician.

If any of the following side effects occur, check with the physician who prescribed the medicine as soon as possible:

• Fainting
• Shortness of breath or difficulty breathing
• Fast, pounding, or irregular heartbeat
• Swollen feet, ankles, wrists.

Other side effects may occur. Anyone who has unusual symptoms after taking alpha blockers should get in touch with his or her physician.

Interactions

Doxazosin (Cardura) is not known to interact with any other drugs. Terazosin (Hytrin) may interact with nonsteroidal anti-inflammatory drugs, such as ibuprofen (Motrin), and with other blood pressure drugs, such as enalapril (Vasotec), and verapamil (Calan,Verelan). When drugs interact, the effects of one or both of the drugs may change or the risk of side effects may be greater.

Key Terms

Arteries

Blood vessels that carry blood away from the heart to the cells, tissues, and organs of the body.

Palpitation

Rapid, forceful, throbbing, or fluttering heartbeat.

Further Reading

Gale Encyclopedia of Medicine. Gale Research, 1999.