Methyldopa

Definition

Antiretroviral drugs are medicines that prevent the reproduction of a type of virus called a retrovirus. The human immunodefiency virus (HIV), that causes acquired immune deficiency syndrome (AIDS), is a retrovirus.

Purpose

Antiretroviral drugs are used to treat infection with the human immunodeficiency virus (HIV), the virus that causes AIDS. These medicines cannot prevent or cure HIV infection, but they help keep the virus in check to minimize other conditions caused by the virus, such as opportunisitic infections.

Viruses are tiny, disease-causing particles that are unable to reproduce on their own. They must invade the cells of other living things and take over the cells' machinery to make more copies of themselves. In the process, they cause illness. HIV is a specific type of virus called a retrovirus. It slowly weakens the immune system by invading and destroying special cells that help defend the body against other kinds of infections.

Like other antiviral drugs, antiretroviral drugs do not kill viruses, because that could also damage or kill the cells the viruses have infected. Instead, these drugs block steps in the process through which viruses reproduce. In this way, antiretroviral drugs slow down damage to the immune system and allow people infected with HIV to feel better and lead more normal lives. However, these drugs do not eliminate HIV, and they do not completely restore the immune system. Although people who take these drugs may feel well most of the time, they may still get serious infections and have other health problems. Furthermore, antiretroviral drugs do not prevent the spread of HIV from an infected person to someone else. People taking these drugs must still observe all precautions to avoid infecting others.

There are three main types of antiretroviral drugs:

• Nucleoside analogs, or nucleoside reverse transcriptase inhibitors (NRTIs), such as didanosine (ddI, Videx), lamivudine (3TC, Epivir), stavudine (d4T, Zerit), zalcitabine (ddC, Hivid), and zidovudine (AZT, Retrovir).
• Non-nucleoside reverse transcriptase inhibitors (NNRTIs), such as delavirdine (Rescriptor), loviride, and nevirapine (Viramune)
• Protease inhibitors, such as indinavir (Crixivan), nelfinavir (Viracept), ritonavir (Norvir) and saquinavir (Invirase).

Many of these drugs became available only in the mid- to late-1990s, and their introduction changed the way physicians treat HIV. Instead of being limited to just a few drugs, physicians now carefully choose combinations of these drugs for patients to take together. In the past, antiretroviral drugs were prescribed only when patients became very ill. But increasingly, they are being given earlier to keep people infected with HIV from getting so sick. Antiretroviral drugs are also sometimes used immediately after exposure to HIV -- in health care workers who are accidentally exposed through needle sticks or blood splashes, for example -- to reduce the chance of infection.

With the rapid advances in antiretroviral drugs, health care professionals are still working out the details of the most effective treatment strategies, exploring which combinations of drugs work best and how soon after infection treatment should begin. Because many of these drugs are relatively new, no one knows how safe they are to use over long periods.

Undergoing treatment with antiretroviral drugs is not an easy process. Patients must be sure to take their medicine at the right times and to schedule their meals around their doses. Scheduling can be complicated, because some of these medicines must be taken with food, while others should be taken on an empty stomach. Because these drugs can cause serious side effects, patients must pay close attention to their health and must make regular visits to their physicians. Anyone considering taking antiviral drugs should be sure to understand all the risks, benefits and requirements of this treatment.

The remainder of this entry describes only nucleoside reverse transcriptase inhibitors, or nucleoside analogs.

Description

The drugs described here are all in the family of antiviral drugs known as nucleoside analogs or nucleoside reverse transcriptase inhibitors (NRTIs). Drugs in this family include didanosine (ddI, Videx), lamivudine (3TC, Epivir), stavudine (d4T, Zerit), zalcitabine (ddC, Hivid), and zidovudine (AZT, Retrovir). These medicines are available only with a physician's prescription and come in liquid, tablet, capsule, and injectable forms.

Recommended dosage

Physicians consider many factors when deciding the correct dosage for each patient, such as body weight and overall general health. Patients using this medicine must carefully follow all instructions, making sure to take the medicine at the proper time and to schedule meals as directed.

Always take antiretroviral drugs exactly as directed. Never take larger or more frequent doses, and do not take the drug for longer than directed. Take only the medicine that has been prescribed, and do not share this medicine with anyone else.

Do not stop taking this medicine without checking with the physician who prescribed it. The only exception is for patients who have severe nausea, vomiting, and stomach pain. These symptoms could be signs of inflammation of the pancreas. Patients who have these symptoms should stop taking the medicine and call their physicians immediately. In all other cases, it is very important to keep taking the drugs, even if symptoms improve.

Antiretroviral drugs work best when they are at constant levels in the blood. To help keep levels constant, do not miss any doses. Health care professionals can help patients plan the best times to take their medicine.

Precautions

See a physician regularly while taking antiretroviral drugs.

These drugs may cause serious side effects, including inflammation of the pancreas, bone marrow problems, and nerve damage in the hands and feet. Check with a physician if any new health problems develop during treatment with this medicine.

Although antiretroviral drugs may make people with HIV feel much better, the drugs will not prevent the spread of HIV from an infected person to someone else. People being treated with these drugs must continue to observe all precautions to prevent the spread of HIV. Health care professionals will discuss these precautions with any patients who are not familiar with them.

Special conditions

People with certain medical conditions or who are taking certain other medicines may have problems if they take antiretroviral drugs. Before taking these drugs, be sure to let the physician know about any of these conditions:

Anyone who has had unusual reactions to antiretroviral drugs 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.

Some forms of antiretroviral drugs contain large amounts of sodium. Anyone on a low-sodium diet should tell his or her physician.

People with phenylketonuria should be aware that some forms of antiretroviral drugs contain phenylalanine.

Some studies show that taking antiretroviral drugs during pregnancy may decrease the chance of a mother infected with HIV passing the virus to her baby. Women who are pregnant and infected with HIV should discuss the use of these drugs with their physicians.

Women who are being treated for HIV infection should check with their physicians about the safety of breastfeeding. Antiretroviral drugs can pass into breast milk. Babies who do not have HIV could be infected through breastfeeding if their mothers are infected.

Beforeu sing antiretroviral drugs, people with any of these medical problems should make sure their physicians are aware of their conditions:

• Alcoholism
• Anemia or other blood problems
• Heart disease
• Kidney disease
• Liver disease
• High blood pressure
• High blood triglycerides
• Pancreatitis (inflammation of the pancreas), now or in the past
• Edema (swelling due to fluid retention)
• Arthritis due to gout
• Toxemia of pregnancy
• Peripheral neuropathy (nerve damage in the hands and feet)
• Phenylketonuria.

Taking antiretroviral drugs with certain other drugs may affect the way the drugs work or may increase the chance of side effects.

Side effects

Some side effects occur early in treatment, but usually go away as the body adjusts to the drug. Among these are anxiety, irritability, restlessness, diarrhea, headache, sore muscles, dry mouth, and sleep problems. These side effects do not require medical treatment unless they continue or are troublesome.

More serious side effects may also occur. If any of the following symptoms occur, check with aphysician immediately:

• Nausea and vomiting
• Stomach pain
• Tingling, numbness, pain, or burning in the hands or feet
• Fever, chills, or sore throat
• Pale skin
• Unusual tiredness or weakness.

Other side effects are possible. Anyone who has new or unusual symptoms while taking antiretroviral drugs should get in touch with his or her physician.

Interactions

Antiretroviral drugs may interact with a larg enumber of other medicines. When this happens, the effects of one or both of the drugs may change or the risk of side effects may be greater. People taking antiretroviral drugs should not take any other medicines without checking with their physicians. Among the many drugs that may interact with antiretroviral drugs are:

• Other antiretroviral drugs
• Alcohol
• Anticancer drugs such as cisplatin (Platinol) and vincristine (Oncovin)
• Antifungal drugs such as itraconazole (Sporanox) and ketoconazole (Nizoral)
• Antiseizure medicines such as valproic acid (Depakene) and phenytoin (Dilantin)
• Blood pressure drugs, such as methyldopa (Aldomet) and furosemide (Lasix)
• Female hormones (estrogens)
• Lithium, used to treat bipolar disorder (manic-depressive illness)
• Sulfonamides (sulfa drugs)
• Tetracyclines.

The list above does not include every drug that may interact with antiretroviral drugs. Be sure to check with a physician before taking any other prescription or nonprescription (over-the-counter) medicine.

Key Terms

Antiviral drugs

Medicines that cure or control virus infections.

Gout

A disease in which uric acid, a waste product that normally passes out of the body in urine, collects in the joints and the kidneys. This causes arthritis and kidney stones.

Immune system

The body's natural defenses against disease and infection.

Inflammation

Pain, redness, swelling, and heat that usually develop in response to injury or illness.

Pancreas

A gland located beneath the stomach. The pancreas produces juices that help break down food and secretes insulin that helps the body use sugar for energy.

Phenylketonuria (PKU)

A genetic disorder in which the body lacks an important enzyme. If untreated, the disorder can lead to brain damage and mental retardation.

Toxemia of pregnancy

A condition in some pregnant women that leads to high blood pressure, swelling due to fluid retention, convulsions, and even coma.

Triglyceride

A substance formed in the body from fat in the diet.

Virus

A tiny, disease-causing particle that can reproduce only in living cells.

Further Reading

For Your Information

Periodicals

• Lipsky, James J. "Antiretroviral Drugs for AIDS." The Lancet 348 (September 21, 1996): 800.
• Williams, Ann B. "New Horizons: Antiretroviral Therapy in 1997." Journal of the Association of Nurses in AIDS Care 8 (July-August 1997): 26.

  Organizations

• Project Inform. 205 13th Street, #2001, San Francisco, CA 94103. (415) 558-8669. http://www.projinf.org.

  Other

• AIDS Clinical Trials Information Service website and telephone information line. Sponsored by Centers for Disease Control and Prevention, Food and Drug Administration, National Institute of Allergy and Infectious Diseases, and National Library of Medicine. 800-TRIALS-A (800-874-2572). http://actis.org.
• HIV/AIDS Treatment Information Service website and telephone information line. Sponsored by Agency for Health Care Policy and Research, Centers for Disease Control and Prevention, Health Resources and Services Administration, Indian Health Service, National Institutes of Health, and Substance Abuse and Mental Health Services Administration. 800-HIV-0440 (800-448-0440). http://www.hivatis.org
• Project Inform National HIV/AIDS Treatment Hotline. 800-822-7422. Hours: Monday - Friday 9 a.m. - 5 p.m.; Saturday, 10 a.m. - 4 p.m. Pacific Time.

Gale Encyclopedia of Medicine. Gale Research, 1999.