6-2 DRUG CLASSIFICATIONS

LEARNING OBJECTIVE: Recall drug groups, the generic and trade names of drugs listed in each drug group, and recognize each drug’s use.

The definition of a drug is any chemical substance that has an effect on living tissue but is not used as a food. Drugs are administered to humans or animals as an aid in the diagnosis, treatment, or prevention of disease or other abnormal condition; for the relief of pain or suffering; and to control or improve any physiologic or pathologic condition. Drugs are classified according to set criteria and fall into three specific areas: general, chemical, and therapeutic.

NOTE

Some drugs may have more than one action.

Drug Nomenclature

Drugs normally have three names: chemical, generic, and trade (brand).

Drug Groups

The types of drugs discussed in this chapter and the correlating drugs in common use are grouped according to pharmacological classes. Only a brief summary is possible here, and the Corpsman who desires a more complete description of each drug should refer to the USP-NF, Drug Facts and Comparisons, the Physicians’Desk Reference, or other drug reference books.

ASTRINGENTS.—Astringents are drugs that cause shrinkage of the skin and mucous membranes. Astringents are mainly used to stop seepage, weeping, or discharge from mucous membranes.

EMOLLIENTS.—Emollients are bland or fatty substances that may be applied to the skin to make it more pliable and soft. They may also serve as vehicles for application of other medicinal substances. Emollients are available as ointments, creams, or lotions.

EXPECTORANTS AND ANTITUSSIVES.— Expectorants and antitussives are commonly used in the symptomatic treatment of the common cold or bronchitis. (See appendix IV, page 1.) Expectorants are more accurately known as bronchomucotropic agents. These agents assist in the removal of secretions or exudate from the trachea, bronchi, or lungs. They act by liquefying viscid mucous or mucopurulent exudates. Therefore, they are used in the treatment of coughs to help expel these exudates and secretions. Antitussives are agents that inhibit or suppress the act of coughing. Other cold and allergy relief preparations are discussed later in this lesson.

NASAL DECONGESTANTS.—Nasal decon­gestants reduce congestion and the swelling of mucous membranes. They are used for the temporary relief of nasal congestion due to the common cold, nasal congestion associated with sinusitis, and to promote nasal or sinus drainage. Nasal decongestants are also used to relieve eustachian tube congestion. Nasal decongestants are often combined with antihistamines, antitussives, and expectorants to relieve the symptoms of colds, allergies, and sinusitis.

ANTIHISTAMINES.—Antihistamines are used to counteract the physical symptoms that histamines cause. Histamine, a substance released by mast cells distributed in connective tissues usually near blood vessels, promotes some of the reactions associated with inflammation and allergies, such as asthma and hay fever. Antihistamines may cause drowsiness, so patients should be warned against driving or operating machinery while taking this type of medication.

HISTAMINE H2 RECEPTOR ANTAGO­NISTS.— Histamine H2 receptor antagonists block histamines that cause an increase of gastric acid secretion in the stomach. Histamine H2 receptor antagonists are effective in preventing complications of peptic ulcer disease and alleviating symptoms of this disease.

ANTACIDS.—Antacids are drugs used to counteract hyperacidity in the stomach. Normally, there is a certain degree of acidity in the stomach. An excess of acid can irritate the mucous membranes and is commonly known as indigestion, heartburn, or dyspepsia. In some disease states, the gastrointestinal tract may become excessively acidic (very low pH), causing diarrhea or leading to peptic ulcer formation. Antacids may interfere with the body’s ability to use many drugs. For this reason, oral drugs normally should not be taken within 2 hours of taking an antacid.

NOTE

It is important for you to be aware of the significance of the sodium content of most antacids, particularly for cardiac patients or patients on a low-sodium diet.

ANTISEPTICS, DISINFECTANTS, AND GERMICIDES.—These agents are primarily intended for the prevention of infections by destroying bacteria or preventing their growth. The differences among them are based primarily on degree of activity and how they are used. Antiseptics suppress the growth of microorganisms. Germicides kill susceptible organisms. Disinfectants are agents used to disinfect inanimate objects and are primarily germicidal in their action. All of these agents are for external use only, unless otherwise indicated. (See appendix IV, pages 3 and 4.)

SULFONAMIDES.—Sulfonamides were the first effective chemotherapeutic agents to be available in safe therapeutic dosage ranges. They were the mainstay of therapy of bacterial infections in humans before the introduction of the penicillins in 1941. Sulfonamides are synthetically produced and are effective against both gram-positive and gram-negative organisms. (See appendix IV, page 5.)

PENICILLINS.—Penicillin is one of the most important antibiotics. It is derived from a number of Penicillium molds commonly found on breads and fruits. The mechanisms of action for the penicillins isthe inhibition of cell wall synthesis during the reproductive phase of bacterial growth. It is one of the most effective and least toxic of the antimicrobial agents. (See appendix IV, page 5.)

CEPHALOSPORINS.—The cephalosporins are a group of semisynthetic derivatives of cephalosporin C, an antimicrobial agent of fungal origin. They are structurally and pharmacologically related to the penicillins. Because the cephalosporins are structurally similar to the penicillins, some patients allergic to penicillin may also be allergic to cephalo­sporin drugs. The incidence of cross-sensitivity is estimated to be 5 to 16 percent.

This family of antibiotics is generally divided into generations:

The main differences among the groups is the change in the antibacterial spectrum. The third generation agents have a much broader gram-negative spectrum than the earlier generations.

TETRACYCLINES .—Tetracyclines, introduced in 1948, were the first truly broad-spectrum antibiotics. They include a large group of drugs with a common basic structure and chemical activity. The most important mechanism of action of the tetracyclines is the blocking of the formation of polypeptides used in protein synthesis. Because of their broad spectrum of activity, tetracyclines are most valuable to treat mixed infection, such as chronic bronchitis and peritonitis; however, they are drugs of choice for only a few bacterial infections. Tetracycline is also used as a topical preparation to treat acne.

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.

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 nephro­toxicity, 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.

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.

ANTIPARASITICS.—Antiparasitics are agents that are destructive to parasites. Parasitic infections or infestations account for the largest number of chronicdisabling 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.

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 ofany 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.

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.

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).

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.

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 CNS depressants 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.

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.

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.

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. Psychothera­peutic 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.

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.

GENERAL AND LOCAL ANESTHETICS.— Generally speaking, anesthesia means “without feeling.” Consequently, we apply the word to drugs that produce insensibility to pain. The field of anesthesia is a highly specialized one.

General anesthetics are usually gas or vapor and are administered by inhalation. Anesthesiology is a highly specialized field, and the administration of a general anesthetic should never be undertaken without the supervision of a medical officer. There may be times, however, when you, as a Hospital Corpsman, are called upon to assist by administering general anesthesia. You should, therefore, acquaint yourself with the most commonly used general anesthetics and their respective properties.

Local anesthetics produce loss of sensation to pain in a specific area or locality of the body, without loss of consciousness or mental capacity. The majority of these drugs are administered parenterally or topically.

OXYTOCICS.—Oxytocics are drugs that produce a rhythmic contraction of the uterus. Their action is selective for the uterus, although other smooth muscles are affected. (See appendix IV, page 18.)

Biological Agents

Biological agents are prepared from living organisms or their products. The chief purpose served by these preparations in the Navy is the immunization of personnel against infectious disease. They may, however, be used in the treatment of disease or act in a diagnostic capacity. Dosage and routes of administration are described in BUMEDINST 6320.1.

Biologicals include serums, viruses, toxins, antitoxins, antigens, and bacterial vaccines.

Manufacturers of these products must be licensed by the Secretary of the Treasury. Their products are monitored by the U.S. Public Health Service.

The label that must be placed on each package will bear the name, address, and license number of the manufacturer. It will also list the name of the product, lot number, date ofmanufacture (or expiration), period of potency, and the minimum potency (or the fact that there is no standard of potency).

FACTORS TO BE REMEMBERED CONCERNING BIOLOGICALS.—Most immu­nizing agents that are used in routine procedures may be obtained through normal supply channels. (Yellow fever vaccine must be ordered from activities that have been designated as supply points for this biological.) Biologicals must be stored in a cool, dry, andpreferably dark place. (Yellow fever vaccine must be maintained in a frozen state until prepared for use.) All biological products should be examined periodically, and a thorough examination for deterioration will be held immediately preceding their use.

EXAMINATIONS OF PARENTERAL SOLUTIONS.—Solutions are examined at least three times at the activity at which they are ultimately used:

  1. Upon receiving the solution.
  2. Periodically while in storage.
  3. Immediately preceding use. Parenteral solutions, unless the label states otherwise, must be free of turbidity or undissolved material. All solutions should be inverted and gently swirled to bring any sediment or particulate matter into view. A well-illuminated black or white background will facilitate this examination.

Parenteral solutions may be unfit for use because of

There is no set rule that can be applicable in regards to any of these factors. Therefore, to ensure suitability for use, a regimented program of inspection is necessary.

IMMUNIZING AGENTS.—Following is a descriptive list of the most common immunizing agents used by the U.S. armed forces to inoculate military personnel against disease.

Diphtheria Antitoxin.—Diphtheria antitoxin is a transparent or slightly opalescent liquid, nearly colorless, and has a very slight odor due to its preservative. It is a sterile solution of antitoxic substances obtained from the blood serum or plasma of a healthy horse immunized against diphtheria toxin.

Tetanus Antitoxin.—Tetanus antitoxin is a sterile solution of antitoxic substances that are usually obtained from the blood serum or plasma of a healthy horse that has been immunized against tetanus toxin or toxoid. Tetanus antitoxin contains not more than 0.4 percent cresol or 0.5 percent phenol as a preservative. It is slightly opalescent with a yellow, brown, or greenish color, depending upon the manufacturer. There will be a slight odor of the preservative used.

Tetanus Toxoid.—Tetanus toxoid is a sterile solution of the growth of the tetanus bacillus,

Clostridium tetani, which has been treated with formaldehyde. It is a brownish yellow or slightly turbid liquid, usually having the distinctive odor of formaldehyde.

Alum Precipitated Diphtheria and Tetanus Toxoids and Pertussis Vaccines Combined (DPT).— This is a markedly turbid, whitish liquid. It is nearly odorless or may have a slight odor of the preservative. It is a sterile suspension of the precipitate obtained by treating the mixture of diphtheria toxoid, tetanus toxoid, and pertussis vaccine with alum and combining in such proportions as to ensure an immunizing dose of each in the total dosage as listed on the label.

Cholera Vaccine.—Cholera vaccine is a suspension of killed cholera, Vibrio comma, in a suitable diluent, usually normal saline. The vaccine presents a turbid appearance, and there may be a slight odor due to the preservative. On storage, autolysis may occur so that the vaccine may become almost as clear as water.

Poliovirus Vaccine.—There are two kinds of polio vaccine: Inactivated poliovirus vaccine (IPV), which is the shot recommended in the United States today, and a live, oral polio vaccine (OPV), which consists of drops that are swallowed. Until recently, OPV was recommended for most children in the United States. OPV helped us rid the country of polio, and it is still used in many parts of the world.

Both vaccines give immunity to polio, but OPV is better at keeping the disease from spreading to other people. However, for a few people (about one in 2.4 million), OPV actually causes polio. Since the risk of getting polio in the United States is now extremely low, experts believe that using oral polio vaccine is no longer worth the slight risk, except in limited circumstances.

Inactivated poliovirus vaccine (IPV) must be stored between 2°C and 8°C (24°F and 46°F). The vaccine is clear and colorless, and it should be administered intramuscularly or subcutaneously.

ORAL POLIOVIRUS VACCINE MUST NEVER BE ADMINISTERED PARENTERALLY. To maintain potency, OPV must be stored in the freezer compartment of the refrigerator. It should be noted that certain forms of this vaccine will remain fluid at temperatures above - 14°C. If frozen, after thawing, agitate the vaccine to ensure homogeneity of its contents before use. Once the temperature rises above 0°C, the vaccine MUST BE USED WITHIN 7 DAYS. During this period, it must be stored below 10°C.

Yellow Fever Vaccine.—This vaccine is a dull, light orange, flaky or crust-like desiccated mass that requires rehydration immediately before use. It must be stored at or below 0°C until rehydration is effected with sterile sodium chloride injection USP.

Plague Vaccine.—The vaccine for plague is a sterile suspension of killed plague bacilli in an isotonic solution. The strain of bacilli used has been selected for its high antigenic efficiency. The vaccine is a turbid, whitish liquid with little or no odor. The presence of any precipitate is reason to suspect contamination.

Influenza Virus Vaccine.—The influenza virus vaccine is prepared from the allantoic fluid of incubated fertile hen eggs. It is a slightly hazy fluid, the result of minute amounts of egg protein. Its color varies from gray to very faint red, depending upon the method of manufacture.

The duration of immunity is probably no longer than a few months, which necessitates repeating the inoculation before the expected seasonal occurrence.

Do not inoculate individuals who are known to be sensitive to eggs or egg products, or personnel suffering from upper respiratory infections.

Dried Smallpox Vaccine.—This vaccine is prepared directly from calf lymph, purified, concentrated, stabilized, and dried by lyophilization. Dried smallpox vaccine is much more stable than the conventional liquid. When stored at or below 25°C, it retains its full potency for 18 months. When reconstituted and stored below 4°C (preferably 0°C), it retains its full potency for 3 months.

Smallpox is no longer considered to be a threat to world health, and immunizations against it are no longer required. However, a general knowledge of the disease and its prevention is important.

Anthrax Vaccine.—The anthrax vaccine for humans licensed for use in the United States is a cell-free filtrate vaccine (using dead as opposed to live bacteria). Inspect the vaccine visually for particulate matter and discoloration before administration. Anthrax vaccine should be stored between 2°C and 8°C (refrigerator temperature); it must not be frozen. Do not use the vaccine if the expiration date listed on the package has expired.

The vaccine should be administered only to healthy men and women from 18 to 65 years of age. It should NOT be administered to pregnant women.

The immunization consists of three subcutaneous injections given 2 weeks apart, followed by three additional subcutaneous injections given at 6, 12, and 18 months. Annual booster injections of the vaccine are required to maintain immunity.