Acquired Immunodeficiency Syndrome

Acquired Immunodeficiency Syndrome (AIDS), human viral disease that ravages the immune system, undermining the body’s ability to defend itself from infection and disease. Caused by the human immunodeficiency virus (HIV), AIDS leaves an infected person vulnerable to opportunistic infections. Such infections are harmless in healthy people, but in those whose immune systems have been greatly weakened, they can prove fatal. Although there is no cure for AIDS, new drugs are available that can prolong the life spans and improve the quality of life of infected people.

Infection with HIV does not necessarily mean that a person has AIDS. Some people who have HIV infection may not develop any of the clinical illnesses that define the full-blown disease of AIDS for ten years or more. Physicians prefer to use the term AIDS for cases where a person has reached the final, life-threatening stage of HIV infection.

Acne

Acne, eruptive skin disease. It is primarily a disorder of the sebaceous follicles of the skin and appears most often on the face, neck, and back. The natural secretion, or sebum, of the follicles accumulates and mixes with dust and dirt. The follicles and surrounding tissue become inflamed and blackheads appear. If the follicle opening completely closes, the accumulated sebum is degraded by bacteria and forms a cyst.

Acne vulgaris, the most common form, is usually associated with adolescence but may also occur in adults. A severe form of the disorder is known as acne conglobata. Other forms of acne are also observed, such as the chloracne caused by chlorinated compounds. In acne rosacea, the capillaries in the cheeks, forehead, and nose are swollen with blood and the oil glands in the skin become infected.

Acne in adolescence results primarily from hormonal changes taking place in the body; the hormones stimulate sebum production. Outbreaks cannot be prevented by a controlled diet and are not a sign of uncleanliness. Good hygiene should be observed, however, to prevent more serious infections. Severe acne may be treated by antibiotics, benzoyl peroxide, or vitamin A derivatives. Severe acne in adults may be a sign of an underlying

Other Drugs

Many other categories of drugs also exist, such as anti-inflammatory, antiallergic, antiParkinson (see Parkinson Disease), antiworm (see Anthelmintic Drugs), diuretic, gastrointestinal, pulmonary, and muscle-relaxant drugs. Often a drug in one category can also be used for problems in other categories. For example, lidocaine can be used as a local anesthetic or as a cardiac drug.

Anticancer Drugs

Anticancer drugs eliminate some cancers or reduce rapid growth and spread. These drugs do not affect all cancers but are specific for cancers in certain tissues or organs such as the bladder, brain, liver, or bones. Anticancer drugs interfere with specific cancer-cell components. For example, alkylating agents are cytotoxic (cell-poisoning) drugs that alter the DNA of cancer cells. Vinca alkaloids, chemicals produced by the periwinkle plant, prevent cancer cell division.

Central Nervous System Drugs

Central nervous system drugs—that is, drugs that affect the spinal cord and the brain—are used to treat several neurological (nervous system) and psychiatric problems. For instance, antiepileptic drugs reduce the activity of overexcited brain areas and reduce or eliminate seizures.

Antipsychotic drugs are used to regulate certain brain chemicals called neurotransmitters, which do not function properly in people with psychoses, major mental disorders often characterized by extreme behaviors and hallucinations, such as in schizophrenia. Antipsychotic drugs can often significantly alleviate hallucinations and other abnormal behaviors.

Antidepressant drugs reduce mental depression. Antimanic drugs reduce excessive mood swings in people with manic-depressive illness, which is characterized by behavioral fluctuations between highs of extreme excitement and activity and lows of lethargy and depression. Both types of drugs act by normalize chemical activity in the emotional centers of the brain. Antianxiety drugs, also referred to as tranquilizers, treat anxiety by decreasing the activity in the anxiety centers of the brain.

Sedative-hypnotic drugs are used both as sedatives to reduce anxiety and as hypnotics to induce sleep. Sedative-hypnotic drugs act by reducing brain-cell activity. Stimulatory drugs, on the other hand, increase neuronal (nerve cell) activity and reduce fatigue and appetite.

Analgesic drugs reduce pain and are generally categorized as narcotics and non-narcotics. Narcotic analgesics, also known as opioids, include opium and the natural opium derivatives codeine and morphine; synthetic derivatives of morphine such as heroin; and synthetic drugs such as meperidine and propoxyphene hydrochloride. Narcotics relieve pain by acting on specific structures, called receptors, located on the nerve cells of the spinal cord or brain. Non-narcotic analgesics such as aspirin, acetaminophen, and ibuprofen reduce pain by inhibiting the formation of nerve impulses at the site of pain. Some of these drugs can also reduce fever and inflammation.

General anesthetics, used for surgery or painful procedures, depress brain activity, causing a loss of sensation throughout the body and unconsciousness. Local anesthetics are directly applied to or injected in a specific area of the body, causing a loss of sensation without unconsciousness; they prevent nerves from transmitting impulses signaling pain (see Anesthesia).