The tetracyclines are relatively nontoxic, the most common side effects being mild gastrointestinal disturbances. Allergic reactions and anaphylaxis are rare. Administration to children and pregnant women is not indicated because it may produce discoloration of the teeth and depress bone marrow growth. The major hazard of tetracycline therapy is the overgrowth of resistant organisms, especially Candida and staphylococci.

Tetracyclines should not be administered with milk, milk products, antacids or iron preparations; they combine with metal ions to form nonabsorbable compounds.

Examples of tetracyclines in common use are listed in appendix IV, page 6.

AMINOGLYCOSIDES.-Aminoglycosides are a group of drugs that share chemical, antimicrobial, pharmacologic, and toxic characteristics, and that are effective against most gram-positive and gram- negative organisms. Their method of action is by inhibiting protein synthesis. Aminoglycosides can cause varying degrees of ototoxicity and nephro- toxicity, depending on the particular agent and the dose. Toxicity is more prevalent in the very young or old, in the presence of renal impairment or dehydration, or with the use of diuretics. Because of their high toxicity, aminoglycosides are not recommended when the infective organism is susceptible to less toxic preparations.

Examples of several aminoglycosides are listed in appendix IV, page 7.

MACROLIDES.-Macrolide antibiotics constitute a large group of bacteriostatic agents that inhibit protein synthesis. They are effective against gram-positive cocci, Neisseria, Hemophilus, and mycobacteria. All are similar to penicillin in their antibacterial spectra, and are often used in patients who are sensitive to penicillin. (See appendix IV, pages 7 and 8.)

ANTIFUNGALS.-Antifungal agents inhibit or suppress the growth systems of fungi, dermatophytes, or Candida. Antifungals have not been developed to the same degree as antibacterial agents. Most fungi are completely resistant to the action of chemicals at concentrations that can be tolerated by the human cell. Since there are only a few available for internal use, most antifungal agents are topical. The antifungal agents that are available for systemic use generally produce hepatic or renal dysfunction or other serious side effects. Because of these side effects, systemic antifungals should be limited to serious or potentially fatal conditions. Therapy that includes topical preparations may be provided in conjunction with oral or parenteral antifungal agents.

Examples of several antifungal agents are listed in appendix IV, page 8.

ANTIPARASITICS.-Antiparasitics are agents that are destructive to parasites. Parasitic infections or infestations account for the largest number of chronic disabling diseases known. They are especially prevalent in the tropics or subtropics and in lesser-developed countries where overcrowding and poor sanitation exist. Parasitic infections include protozoal infections (malaria, amebiasis, and to a lesser extent, trichomoniasis), helminthic infections (intestinal worms), and ectopara-sites. Ectoparasites, such as head lice and crab lice, although not disabling, are considered a nuisance and can transmit disease.

Examples of antiparasitics in common use are listed in appendix IV, page 9.

LAXATIVES.-Laxatives are drugs that facilitate the passage and elimination of feces from the colon and rectum. They are indicated to treat simple constipation and to clean the intestine of any irritant or toxic substances (catharsis). Laxatives may also be used to soften painfully hard stools and to lessen straining of certain cardiac patients when defecating. They are contraindicated in certain inflammatory conditions of the bowel, bowel obstruction, and abdominal pain of unknown origin, and should not be used in the presence of nausea and vomiting. Laxatives are classified as irritant, bulk, emollient, or stool softeners. Frequent or prolonged use of any laxative may result in dependence. (See appendix IV, pages 9 and 10.)

ANTIDIARRHEALS.-Antidiarrheals are drugs that are effective in combating diarrhea. Diarrhea is defined as an abnormal frequency and liquidity of fecal discharge. This condition may result from food poisoning, parasitic infestation of the bowel, and gastrointestinal diseases. (See appendix IV, page 10.)

DIURETICS.-The kidney is the primary organ that excretes water-soluble substances (urine) from the body. Diuretics are agents that increase the rate of urine formation. These agents are useful in treating hypertension and edematous conditions, such as congestive heart failure and acute pulmonary edema. However, loss body fluids due to use of diuretics can seriously deplete electrolytes from the system, and care should be taken to monitor and replenish lost sodium and potassium through diet and supplement therapy. (See appendix IV, page 10 and 11)

NON-NARCOTIC ANALGESICS, ANTIPYRETICS, AND ANTI-INFLAMMATORY AGENTS.-Non-narcotic analgesics are drugs that relieve pain without producing unconsciousness or impairing mental capacities. Antipyretics relieve or reduce fevers. Anti-inflammatory agents counteract or suppress inflammation or the inflammatory process. Many of the drugs discussed in appendix IV, page 11, were developed with two or more of these properties.

CENTRAL NERVOUS SYSTEM STIMULANTS.-Certain drugs stimulate the activity of various portions of the central nervous system (CNS). The Manual of the Medical Department (MANMED) is explicit as to the usage of these drugs in the Navy. Primary indications for this class of drugs are narcolepsy, hyperkinesis, and attention deficit disorders in children. Central nervous system stimulants are generally contraindicated in patients with hypertension, arteriosclerosis, symptomatic cardiovascular disorders, agitated states, glaucoma, or history of drug abuse. (See appendix IV, page 12.)

CENTRAL NERVOUS SYSTEM DEPRESSANTS.-Central nervous system (CNS) depressants range in depressive action from mild sedation to deep coma, differing mainly in rapidity, degree, and duration of action. Any of these CNSdepressants may, in sufficient doses, cause respiratory depression. Alcohol use while taking CNS depressants should be avoided. Many of the central nervous system depressants are controlled medications. Refer to the MANMED for control, custody, and accountability guidelines for controlled substances.

Barbiturates comprise a widely used group of CNS depressants. They are used mainly as sedative-hypnotics, anticonvulsants, anesthetics for short anesthesia, and may be used in combination with analgesics to enhance their analgesic effect.

NOTE: Barbiturates may be habit forming. See appendix IV, page 12, for examples of central nervous system depressants.

OPIUM AND OPIUM ALKALOIDS.-The activity of opium is primarily due to its morphine content. The major medical use of opium has been for its antiperistaltic activity, particularly in diarrhea. Opium alkaloids, e.g., morphine and codeine, have replaced opium in medical use. Members of this drug group are used as analgesics, cough sedatives, and for certain types of diarrhea. (See appendix IV, pages 12 and 13.)

NOTE: Warn patients taking opium or opium alkaloids that drowsiness, dizziness, and blurring of vision may occur. For this reason, they should not drive or perform other tasks that require alertness. Also, caution patients against consuming alcohol and other CNS depressants. Patients should notify their physician immediately if shortness of breath or difficulty in breathing occurs.

PSYCHOTHERAPEUTIC AGENTS.- Tranquilizers and mood modifiers are the two primary groups of psychotherapeutic agents. Psychothera- peutic agents are classified as major tranquilizers, minor tranquilizers, and mood modifiers. The mood modifiers have replaced amphetamines as treatment of choice for depressive states. (See appendix IV, pages 13 and 14.)

SKELETAL MUSCLE RELAXANTS.- Skeletal muscle relaxants are used in connection with the treatment of muscle spasm due to various conditions. They may also be used to produce muscular relaxation during surgical anesthesia. Skeletal muscle relaxants may cause drowsiness and impair performance of tasks that require alertness. (See appendix IV, page 14.)

CARDIOVASCULAR AGENTS.-Cardiovascular agents affect the action of the circulatory system. Most of these agents are highly specialized. (See appendix IV, pages 14 and 15.)

VASOCONSTRICTORS.-Vasoconstrictors produce constriction of the blood vessels with consequent rise in blood pressure. (See appendix IV, page 15.)

ANTICOAGULANTS.-Anticoagulants delay or prevent blood coagulation. Before an anticoagulant agent is prescribed and its dosage determined, laboratory testing of the patient's blood-clotting capabilities should be performed.

Examples of commonly used anticoagulants are listed in appendix IV, page 15.

VITAMINS.-Vitamins are unrelated organic substances that occur in many foods and are necessary for the normal metabolic functioning of the body. Vitamins may be water-soluble or fat-soluble. The majority of vitamins are water-soluble. Water-soluble vitamins are excreted in the urine and are not stored in the body in appreciable quantities. The fat-soluble vitamins (A, D, E, and K) are soluble in fat solvents and are absorbed along with dietary fats. Fat-soluble vitamins are not normally excreted in the urine and tend to be stored in the body in moderate amounts.

See appendix IV, page 16, for a listing of several of the major vitamins and their respective properties.