Hospital Corpsman 3 & 2: June 1989

Chapter 7: Pharmacology and Toxicology

Naval Education and Training Command


Introduction

Drug Standards

Medication Administration

Drug Classifications

Nomenclature

Drug Groups

 

Biological Agents

Toxicology

Regulations and Responsibilities Pertaining to Controlled Substances, Alcohol and Dangerous Drugs

References

Introduction

As you advance in rate, you will become more and more involved with the intricacies of administering medicines. Although the drugs and their dosages are prescribed by the medical officer and other authorized prescribers, you, as the hospital corpsman, are involved in their administration. It is necessary for you to learn their sources, composition, methods of preparation and administration, and physiologic and toxicologic action. This chapter is concerned primarily with the action, use, and dosage of drugs.

The subject of pharmacology was known as Materia Medica until 1890 when the current term began to come into use. The subsciences of pharmacology and their specific fields of study are as follows:

Pharmacognoscy - The recognition, quality, purity, and identification of drugs.

Pharmacy - The preparation, stability, preservation, and storage of pharmaceutical preparations.

Dosology - Dosage or amount of drug to be given.

Pharmacodynamics - The response of living tissue to chemical stimulation in the absence of disease. This almost exclusively deals with research and development.

Pharmacotherapeutics - The action of drugs on living tissue in the presence of disease; treatment of the sick.

Toxicology - The toxic or poisonous effects of substances.

The art of treating disease by any method that will relieve pain, cure disease, or prolong life is called therapeutics. Although the average person thinks solely of giving or taking medicine in this respect, it must be remembered that therapy also includes other methods, such as radiological treatment, diathermy, hydrotherapy, and many more.

 Drug Standards

The texts dealing with pharmaceutical preparations include the United States Pharmacopeia and National Formulary (USP-NF) which provides standards for drugs of therapeutic usefulness and pharmaceutical necessity. Inclusion of drugs into this compendia is based on therapeutic effectiveness and popularity. It provides tests for identity, quality, strength, and purity.

The Physicians'Desk Reference is a multiple index of commercially available drugs and is used as an advertising outlet for various drug manufacturers. Pharmaceutical preparations are described as to composition, action and use, administration and dosage, precautions and side effects, dosage forms available, and the common (generic) name of the drug.

Remington's Pharmaceutical Sciences is probably the most widely used text/reference in American pharmacy. It contains all areas relevant to the art/science of pharmacy. The Pharmaceutical Basis of Therapeutics (Goodman and Gilman) is a textbook of pharmacology, toxicology, and therapeutics known as the "blue bible" of pharmacology.

 Medication Administration

The quantity of a drug to be administered at one time or the total quantity administered and the method of administration of drugs is dependant upon several factors. This section will cover some of the methods of administration and some of the factors affecting dosage calculations.

Dosage

The amount of medication to be administered is referred to as the dose. The study of dosage and the criteria which influence it is called posology. The doses given in the United States Pharmacopeia and National Formulary (USP-NF) are average therapeutic doses and are known as "usual adult doses." The following terms are used in connection with doses:

Therapeutic dose - Also referred to as the normal adult dose, the usual dose or average dose, it is the amount needed to produce the desired therapeutic effect. This is calculated on an average adult about 24 years old, weighing approximately 150 pounds.

Dosage range - A term that applies to the range between the MINIMUM amount of drug and the MAXIMUM amount of drug required to produce the desired effect. Many drugs, such as antibiotics, require large initial doses that are later tapered to smaller amounts. Closely associated with this term are MINIMUM dose, the least amount of drug required to produce a therapeutic effect; MAXIMUM dose, the largest amount of drug that can be given without reaching the toxic effect; and the TOXIC dose, the least amount of drug that will produce symptoms of poisoning.

Minimum lethal dose - The least amount of drug than can produce death.

 Factors Affecting Dosage

In the administration of medicines there are many factors that affect the dose, method of administration, and frequency of the dose. Although a physician prescribes the amount to be given, you need to know how and why these quantities are determined. The two primary factors that determine or influence the dose are age and weight.

Age

Age is the most common factor that influences the amount of drug to be given. An infant would require much less than an adult. Elderly patients may require more or less than the average dose, depending upon the action of the drug and the condition of the patient.

The rule governing calculation of pediatric doses is Young's Rule as shown below:

    Age in years    
Age in years + 12

x

Adult dose = child's dose

The age in years of the child is the numerator and the age plus 12 is the denominator. This fraction is multiplied by the normal adult dose.

Example: The adult dose of aspirin is 650 mg. What is the dose for a 3-year-old child?

   3   
3 + 12

x

650 mg
15

= 130 mg

 

Weight

In the calculation of dosages, weight has a more direct bearing on the dose than any other factor, especially in the calculation of pediatric doses. The rule governing calculation of pediatric doses based on weight is Clark's Rule shown below:

   Weight of child (pounds)   
150 pounds

x Adult's dose = Child's dose

The weight in pounds is the numerator and the average adult weight, 150 pounds, is the denominator. This fraction is multiplied by the adult dose.

Example: The adult dose of aspirin is 650 mg. What is the dose for a child weighing 60 pounds?

 60 pounds
150 pounds

x 650 mg = 260 mg

Other factors that influence dosage are:

  1. Sex. Females usually require smaller doses than males.
  2. Race. Blacks usually require larger doses and Asians smaller doses than Caucasians.
  3. Genetic make-up. The genetic structure of the individual may cause peculiar reactions to medications in some patients.
  4. Occupation. Persons working in strenuous jobs may require larger doses than those who sit at a desk all day.
  5. Habitual use. Some patients must take medications chronically, causing their bodies to build up tolerance to the drug. This tolerance may require larger doses than their initial doses to obtain the same therapeutic effect.
  6. Time of administration. Therapeutic effect may be altered depending upon time of administration. Example: Before or after meals.
  7. Frequency of administration. A drug given frequently may need a smaller dose than if administered at longer intervals.
  8. Mode of administration. This has a definite impact on the dose. Example: Injections

 Methods of Administering Drugs

Drugs are introduced into the body by different routes, each serving a specific purpose.

Oral

Oral administration of medications is the most common method. Advantages are (1) convenience, (2) economy, (3) the drug need not be absolutely pure or sterile, and (4) a wide variety of dosage forms are available. Oral medications include tablets, capsules, liquids, and suspensions. Disadvantages include (1) inability of some patients to swallow, (2) slow absorption, and (3) partial or complete destruction by the digestive system. Other routes associated closely with oral administration are SUBLINGUAL and BUCCAL.

Parenteral

Parenteral medications are those introduced by injection. All drugs used by this route must be pure, sterile, pyrogen-free (pyrogens are products of the growth of microorganisms), and in a liquid state. There are several types of parenteral administration.

Inhalation

Inhalation is the introduction of medications through the respiratory system in the form of a gas, vapor, or powder. Inhalation is divided into three major types:

Topical

Ointments, creams, lotions, and shampoos are examples of topical preparations. Topical application serves two purposes: (1) local effect-the drug is intended to relieve itching, burning, or other skin conditions without being absorbed into the bloodstream and (2) systemic effect-the drug is absorbed through the skin into the bloodstream. Example: Nitroglycerin paste

Rectal

The rectal method is preferred to the oral route when there is danger of vomiting or when the patient is unconscious, uncooperative, or mentally incapable.

Vaginal

Suppositories, creams, or tablets are examples of vaginal preparations which are inserted into the vagina to produce a local effect.

 Drug Classifications

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 used on or 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, or to control or improve any physiologic or pathologic condition. A drug may be classified in various categories, depending upon different criteria. Examples are general, chemical, and therapeutic.

 Nomenclature

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

 Drug Groups

The drugs discussed in this chapter are those in common use, or are in the Medical Stock List, and are grouped according to pharmacological classes. Only a brief summary is possible here and the corpsman who desires a more complete study of each drug should refer to the USP-NF or other reference books indicated at the end of this chapter.

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 utilize many drugs. For this reason, most oral drugs should not be taken within 2 hours of taking an antacid. NOTE: As a hospital corpsman, it is important to be aware of the significance of the sodium content of most antacids, particularly in the cardiac patient or patients on a low sodium diet.

Action and Use - Milk of magnesia reacts with gastric acid to form magnesium chloride and has a prolonged duration of action. It is preferably taken on an empty stomach with lots of fluid. Do not use when abdominal pain, nausea, or vomiting is present. Shake well. Prolonged use may result in kidney stones. It also has a laxative effect.

Usual Dose - 5 to 10 ml four to six times a day, up to a maximum of 60 ml. Laxative dose is 15 to 30 ml.

Action and Use - This drug is used in the management of peptic ulcer, gastritis, and gastric hyperacidity. The major advantage of this drug is that no systemic alkalosis is produced. It may cause constipation.

Usual Dose - 15 ml four to six times daily between meals and at bedtime.

Action and Use - Alumina and magnesia oral suspension coats the stomach lining and neutralizes gastric acid. It is less constipating than aluminum hydroxide alone.

Usual Dose - 5 to 20 ml 1 hour after each meal and at bedtime.

Action and Use - This drug coats the stomach lining, neutralizes gastric acid, and reduces flatulence.

Usual Dose - 5 to 10 ml 1 hour after meals and at bedtime.

Action and Use - Magaldrate is the same as alumina and magnesia oral suspension, but is has a lower sodium content.

Usual Dose - 5 to 10 ml between meals and at bedtime.

 Astringents

Astringents are drugs that cause shrinkage of the skin and mucous membranes. They act by precipitating the proteins on the surface layer of the skin and mucus membranes. Their main use is to stop seepage, weeping, or discharge from mucous membranes.

Action and Use - This drug is an astringent wet dressing for the relief of inflammatory conditions of the skin, such as poison ivy, swellings and bruises, insect bites, athlete's foot, or other environmental skin conditions and for superficial external otitis.

Usual Dose - Topical, in a 1:10 to 1:40 solution.

Action and Use - Calamine lotion is used in the treatment of various skin afflictions in the same way as aluminum acetate. It is an astringent and protective, which is used externally. It should not be applied to blistered, raw, or oozing areas of the skin.

Usual Dose - Apply to the affected area two to four times daily and at bedtime.

 Adsorbents

An adsorbent is a drug that attaches another substance to its surface. These drugs are used to adsorb undesirable substances.

Action and Use - This drug forms an effective barrier between any remaining particulate material and the gastrointestinal mucosa, thus inhibiting gastrointestinal absorption. It is used as an emergency treatment in poisoning by most drugs and chemicals.

Usual Dose - 30 to 100 g within 30 minutes after ingestion of toxic substances. It is administered as a slurry and ingested by the patient or administered through a nasogastric or lavage tube.

 Emollients

Emollients are bland or fatty substances that may be applied to the skin to make it more pliable and soft, and may also serve as vehicles for application of other medicinal substances. They are available as ointments, creams, or lotions. Examples not discussed include Keri-Lotion, Eucerin-Lotion, and Lubriderm.

Action and Use - Cocoa butter is an excellent emollient with a pleasant odor. It is ideal for the treatment of chapped skin and lips, cracked nipples, or minor irritated or abraded skin areas.

Action and Use - This is a smooth creamy ointment of wool fat. It is an ideal emollient for dry, scaly skin conditions.

Action and Use - Petrolatum is a highly occlusive and good emollient. It may not release some drugs when used as an ointment base.

Action and Use - This is a white petrolatum containing approximately 20 percent zinc oxide powder. It is used as an emollient with slightly astringent properties, and because of its opaqueness it is ideal for protecting sensitive skin from the sun.

 Expectorants and Antitussives

Expectorants, more accurately known as bron chomucotropic agents, are drugs used to assist in the removal of secretions or exudate from the trachea, bronchi, or lungs. They act by liquifying viscid mucus or mucopurulent exudates, i.e., they are decongestants. Therefore, they are used in the treatment of coughs to help expel these exudates and secretions. Antitussives are agents that specifically inhibit or suppress the act of coughing. They should not be used to suppress productive coughing. Expectorants and antitussives are most commonly used in the symptomatic treatment of the common cold or bronchitis. Other cold and allergy relief preparations are discussed later in this chapter.

Antiseptics, Disinfectants and Germicides

These drugs 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 and are used topically; germicides kill susceptible organisms; and disinfectants are agents used on inanimate objects and are primarily germicidal in their action. All of these agents are for external use only unless otherwise indicated.

 Anti-Infectives

Antibiotics are chemical compounds produced as the result of metabolic activity of micro-organisms or produced synthetically. They inhibit the growth of susceptible microorganisms or kill them through the destruction of necessary enzymes. Antibiotics that are sufficiently non-toxic to the host are used as chemotherapeutic agents in the treatment of infectious diseases of man, animals, and plants. They can be administered orally, topically, or parenterally.

Antibacterial Agents

The five basic mechanisms of action for the antimicrobial agents are

  1. inhibition of the synthesis of the bacterial cell wall,
  2. affecting the cell wall permeability,
  3. inhibition of protein synthesis by affecting ribosomal activity,
  4. affecting nucleic acid metabolism, and
  5. the antimetabolites that compete with necessary enzymes.


To be of practical value in the treatment of infection, an antimicrobial agent must exert it effects upon the invading microorganism without seriously damaging the cells of the host. The following are groups of antimicrobial agents and their general mechanisms of action.

Sulfonimides

The sulfonimides 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. All the sulfonimides are synthetically produced and contain the para-amino-benzene sulfanilamide group. The spectrum of activity for all the sulfonimides is similar and all are effective against both gram-positive and gram-negative organisms. They are primarily bacteriostatic and act as an antimetabolite (competitor) to para-aminobenzoic acid (PABA) in susceptible organisms. PABA is required in the formation of folic acid.

Excretion of the sulfonimides is chiefly through the kidneys. Some of the sulfonimides are relatively insoluble in acidic or neutral solutions so there is some danger that a sulfonimide would precipitate out of solution leading to crystal formation, hematuria, or possibly renal shutdown. Forcing fluids to keep the urine dilute or administering alkaline solutions can help to prevent precipitation of sulfonimides. With the newer sulfonimides, this is not a major concern since many of them are soluble in acidic solutions.

Although the sulfonimides have, for the most part, been replaced with other agents, there is still a significant demand in certain types of infection, most notable urinary tract infections, such as acute cystitis or prostatitis, and in cases of acute otitis media. The following lists some of the more common sulfonimides.

 Penicillins

Penicillin is one of the most important of the antibiotics. It is derived from a number of Penicillium molds commonly found on breads and fruit. The mechanisms of action for the penicillins is the 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.

Benzylpenicillin (Penicillin G) is the prototype form for all the penicillins. It is highly effective against many of the gram-positive cocci, and, to a lesser extent, the gram-negative cocci. Semisynthetic preparations have been produced to attempt to overcome some of the problems of the naturally occurring penicillins, i.e., instability in an acid medium, rapid renal excretion, susceptibility to penicillinase, and a high incidence of hypersensitivity. Significant differences among the agents include resistance to gastric acid inactivation, resistance to inactivation by penicillinase, and the spectra of antimicrobial activity.

Although the penicillins are virtually nontoxic to mammalian cells, there is a significant incidence of anaphylaxis in varying degrees. Reactions include skin rash, contact dermatitis, mild gastrointestinal upset, oral lesions, and fever. Because of the basic structure, there is a high degree of cross-sensitivity among the various forms.

Penicillin is effective in the treatment of:

 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 be allergic to a cephalosporin drug. The incidence of cross-sensitivity is estimated to be 5 to 16 percent. Their antibacterial activity is due to inhibition of cell wall synthesis.

This family of antibiotics is generally divided into generations: first generation, cephadrine and cefazolin; second generation, cefoxitin, and third generation, cefotaxime. The main differences between groups is the change in the antibacterial spectrum. The third generation agents have a much broader gram-negative spectrum than the earlier generations.

 Tetracyclines

The 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 blocking the formation of polypeptides used in protein synthesis. Because of their broad spectrum of activity, tetracyclines are most valuable in the treatment of 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 in the treatment of acne.

The tetracyclines are relatively non-toxic, 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 Monilia 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

The aminoglycosides are a group of drugs sharing chemical, antimicrobial, pharmacologic, and toxic characteristics. They are effective against most gram-positive and gram-negative organisms; the 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 presence of renal impairment, in the very young or old, dehydration, or with the use of diuretics. Because of their high toxicity, they are not recommended when the infective organism is susceptible to less toxic preparations.

 Macrolides

The 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.

 Miscellaneous Antibiotics

In addition to the previously mentioned antiinfectives, there are several other agents that are effective in the treatment of different organisms.

 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 agents that are available for systemic use generally produce hepatic or renal dysfunction or other serious side effects; because of this, systemic antifungals should be limited to serious or potentially fatal conditions. When using oral or parenteral antifungal agents, provide concomitant therapy with topical preparations.

 Antiparasitics

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, i.e., malaria, amebiasis, and to a lesser extent, trichomoniasis; helminthic infections (intestinal worms), and ectoparasites. Ectoparasites, 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 for the treatment of 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.

 Antidiarrheals

 Diuretics

The kidney is the primary organ that excretes water-soluble substances from the body. Diuretics are agents that increase the rate of urine formation. The term diuresis has two separate connotations: one refers to the net loss of solute and water, the other to the increase in volume per se. Sometimes maintenance of an adequate urine volume is justification for using diuretics. The most important indication is for the production of a negative extracellular fluid balance. Diuretics are useful in the treatment of hypertension, edematous conditions, i.e., congestive heart failure, and acute pulmonary edema.

 Non-Narcotic Analgesics and Antipyretics

Analgesics are drugs that relieve pain without producing unconsciousness or impairing mental capacities. Many of these drugs also have an antipyretic and/or an anti-inflammatory effect. Antipyretics are drugs that lower increased body temperatures. Included in this group are the nonsteroidal anti-inflammatories.

 Central Nervous System - Stimulants

Certain drugs stimulate the activity of various portions of the central nervous system (CNS). Chapter 21 of 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.

 Central Nervous System - Depressants

This large group of drugs ranges in depressive action from mild sedation to deep coma, differing mainly in rapidity, degree, and duration of action. Many of the central nervous system depressants are scheduled medications. Chapter 21 of MANMED describes requirements for control, custody, and accountability of all controlled substances. Any of these agents may, in sufficient doses, cause respiratory depression. Any use of alcohol should be avoided with any of these medications. NOTE: Barbiturates may be habit forming.

The barbiturates are a widely used group of CNS depressants that have the same general action. They are used mainly as sedative-hypnotics, anticonvulsants, anesthetics for short anesthesia, and they may be used in combination with analgesics to potentiate their analgesic effect.

 Opium and Its Alkaloids

The most important alkaloids of opium are morphine and codeine. All of the other opiate derivatives are severe respiratory depressants. Small doses dull the cough reflex and larger doses abolish it. These drugs may cause constipation by diminishing the secretions of the gastrointestinal tract and increasing the tone of the intestinal muscles to the point of spasm. Members of this class are used as analgesics, cough sedatives, and for certain types of diarrhea.

 Psychotherapeutic Agents

Tranquilizers and mood modifiers are the two primary groups of psychotherapeutic agents. They are classified as major tranquilizers, minor tranquilizers, and mood modifiers. The mood modifiers have replaced the amphetamines as treatment of choice for depressive states.

 Skeletal Muscle Relaxants

These agents may be used to produce muscular relaxation during surgical anesthesia. More often these drugs are used in connection with the treatment of muscle spasm due to various conditions. All of these drugs may cause drowsiness and impair performance of tasks that require alertness.

 Cardiovascular Agents

Cardiovascular drugs comprise a large group that affect the action of the circulatory system. Most of these agents are highly specialized and will be listed according to their principal action.

 Vasodilators

These drugs produce vasodilation by relaxing the smooth muscle of the arteries, thereby lowering the blood pressure. This fall in blood pressure is the most important pharmacological action desired.

 Vasoconstrictors

The opposite of vasodilators, these drugs produce constriction of the blood vessels with consequent rise in blood pressure.

 Hemostatics

These are drugs that control external bleeding by forming a clot.

 Anticoagulants

These drugs delay or prevent blood coagulation. Use of these agents requires laboratory facilities to determine prothrombin time and partial thromboplastin time values to determine dosages.

Vitamins

Vitamins are essential substances for maintenance of normal metabolic functions. They are not synthesized in the human body in normally adequate quantities; therefore, they must be provided from outside sources.

 Anesthetics

Generally speaking, anesthesia means "without feeling"; consequently, we apply the word to drugs that produce insensibility to pain. The field today is a highly specialized one.

 Autonomic Drugs

The autonomic nervous system, also called the visceral or involuntary nervous system, controls the autonomic functions of the body. Drugs that affect the autonomic nervous system are highly specialized and therefore are classified according to their effect.

Sympathomimetic Drugs

These drugs stimulate the structures controlled by the sympathetic (or adrenergic) nerves and start adrenal medullary discharge of epinephrine. The two main drugs, epinephrine and phenylephrine are discussed under the vasoconstrictive drugs earlier in this chapter.

Sympatholytic Drugs

Also called adrenergic blocking agents, these drugs block the action of the sympathomimetic amines or block sympathetic outflow. The alpha-adrenergic blocking agents block the vasoconstricting effects of epinephrine and norepinephrine, thereby lowering the blood pressure. The beta-adrenergic blocking agents block the cardiac and vasodilating effects of epinephrine and the cardiac effects of norepinephrine, thereby lowering the force of cardiac contractions and decreasing the heart rate.

 Oxytocics

These are drugs that produce a rhythmic contraction of the uterus. Their action is selective for the uterus, although other smooth muscles are affected.

 Antihistamines

Histamine is a substance found in tissue that has an important role in allergic reactions. This has led to the development of compounds that oppose its action. These drugs apparently compete with histamine at the site of action. The drugs listed here are representative of the entire group many of which are used for the symptomatic relief of seasonal rhinitis. Any of these drugs may cause drowsiness.

 Histamine H2 Receptor Antagonists

 Cold Relief Preparations

 Biological Agents

Biologicals are agents that 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 series.

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 of manufacture, or expiration, period of potency, and the minimum potency or the fact that there is no standard of potency.

Immunizing Agents

 Factors to be Remembered in Connection with Biologicals

  1. Acquisition. 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.
  2. Storage. Biologicals will be stored in a cool, dry, and preferably dark place. Yellow fever vaccine must be maintained in a frozen state until prepared for use.
  3. Examination. All biological products should be examined periodically, and a minute examination for deterioration will be held immediately preceding their use.

 Examinations of Parenteral Solutions

Solutions will have been 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 in order 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:

  1. Deterioration from prolonged storage.
  2. Accidental contamination occurring upon original packaging.
  3. Defects that may develop in containers or seals.

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.

 Toxicology

Toxicology is the science of poisons. It is concerned with the detection, isolation, and quantitative estimation of poisons, their chemical and physiologic effect on the ordinarily healthy organism, and the antidotes for their toxic effects.

A poison is a substance that may produce death, serious illness, or harmful effects when introduced into the body in a relatively small quantity.

The effects of poisons may be local or remote and some poisons have both effects. LOCAL EFFECT means direct action on the part to which the poison is applied, such as corrosion and irritation. REMOTE EFFECT means the action of the poison on some organ remote from the site of application or point of introduction. Sometimes, a poison shows no effect or only a slight one, until several doses have been taken. Then suddenly, an effect is produced that nearly equals that produced by taking the whole amount at one time. This is known as CUMULATIVE EFFECT.

The effect of a poison depends upon its solubility, the method of its introduction into the body, and the rapidity of its absorption into the system. The method of introduction may determine its toxicity. For example, snake venom taken into the mouth and perhaps even into the stomach during first aid treatment of snakebite is not ordinarily harmful, but snake venom injected parenterally is extremely poisonous.

There are various ways in which poisons may be introduced into the body, the most common being by mouth, inhalation, and injection. Poisons taken by mouth enter the circulation through absorption from the stomach and in- testine. Those inhaled enter the circulation through the lungs. When parenterally injected or deposited into the urethra, rectum, or vagina, poisons enter the circulation through absorption from the body tissues in those areas. If the injection is intravenous, the poisons are directly introduced into the bloodstream. Poisons may also be introduced by application to open wounds and to the unbroken skin. After entering the circulation, a poison is carried by the blood to the tissues and organs susceptible to its action and attacks them.

Most of the excretion of poisons from the body occurs in the kidneys, liver, gastrointestinal tract, and skin. Poisons may be excreted from the system unchanged or in the form of other compounds into which they have been transformed by the action of various body organs and tissues. The most damaging effects of some poisons are found at the point of excretion.

Various conditions of the individual may modify the actions and effects of poisons on the body. The age of the victim makes a great deal of difference, with young children being more susceptible to poisons than adults. Conditions caused by poisons will vary because of a personal idiosyncrasy; that is to say, some persons by nature are unusually sensitive to certain poisons, while others possess a natural tolerance for certain poisons that is not the result of habitual use. Through habitual use of certain poisons, especially narcotics, most persons may become so accustomed to their effects that they are not poisoned when taking doses that would ordinarily prove lethal in the unaddicted. It occasionally happens, however, that continual external use of chemical substances results in hypersensitivity. The actions of poisons may be considerably modified by disease, some diseases increasing and others lessening the action of poisons. In the latter case, large doses are usually required to produce the desired effect.

Poisoning may either be acute or chronic. Acute poisoning is the condition brought on by taking an overdose. Chronic poisoning is the condition brought on by taking repeated doses of a poison or as the result of the absorption of the poison over a long period.

Classification of Poisons

Gaseous Poisons

These poisons are present in the gaseous state and if inhaled, destroy the capability of the blood as a carrier of oxygen and irritate or destroy the tissues of the air passages and lungs. When in contact with the skin and mucous membranes, gaseous poisons produce lacrimation, vesication, inflammation, and congestion. Examples are carbon monoxide, carbon dioxide, hydrogen sulfide, sulfur dioxide, ammonia gas, chlorine gas, and chemical warfare agents

Inorganic Poisons

Inorganic poisons fall into two classes:

  1. Corrosives, which are substances that rapidly destroy or decompose the body tissues at point of contact. Some examples are hydrochloric, nitric, and sulfuric acids; phenol; sodium hydroxide; and iodine.
  2. Metals and their salts, which are corrosive and irritate locally, but whose chief action occurs after absorption when they damage internal organs, especially those of excretion.

Some examples are arsenic, antimony, copper, iron, lead, mercury, radioactive substances, and tin.

Alkaloidal Poisons

These poisons are nitrogenous plant principles that produce their chief effect on some part of the central nervous system. Some examples are atropine, cocaine, morphine, and strychnine.

Nonalkaloidal Poisons

These poisons include various chemical compounds, some obtained from plants, having hypnotic, neurotic, and systemic effects. Some examples are barbiturates, salicylates, digoxin, and turpentine.

 Effects and Symptoms of Poisons

For convenience of study, the following general classification of poisons is based according to their effects on the body and the general symptoms of poisoning.

 Poison Control Centers

The United States Public Health Service has established a clearing house for poison information. Its chief purpose is to interchange information with many local poison control centers established throughout the country. The centers have been established at major medical centers and operate on a 24-hour a day basis. Every medical facility should make an attempt to use the services of the poison control center contiguous to its activity.

 Treatment of Poisoning

The basic procedure is as follows:

  1. Remove the bulk of the poison out of the stomach quickly. Removal of the poison from the stomach may be accomplished by the use of emetics and by washing out the stomach through use of a stomach tube.
  2. Administer an antidote for the remainder of the poison left in the stomach.
  3. Eliminate from the system that portion of the poison that has been absorbed.
  4. Treat the symptoms as they arise.
  5. Take possession of all foods, medicines, vomitus, feces, urine, and anything that may be of value in determining the identity of the poison and whether taken accidentally or intentionally, or criminally administered.

Cases of poisoning are frequently encountered where the services of a physician or poison control center are unavailable. In these cases, it often happens that it is impossible to obtain much or any information relative to the nature or type of poison taken. Since any delay in treatment may result in serious consequences, every hospital corpsman should possess some practical knowledge of how to manage a poisoning case when the nature of the poison is unknown.

For the purpose of general treatment in unknown poisons, the case may be considered as one of two kinds. It may either be a case in which the local effects of the poison have injured the mucous lining of the mouth, esophagus, and stomach to an extent contraindicating the use of instruments or emetics for evacuating the stomach or it may be a case where the poison has had little or no effect on the mucous lining of the alimentary tract and therefore one in which it would be safe to use a stomach tube or an emetic.

Poisonings coming under the classification of corrosives generally produce conditions such as mentioned in the first instance. They have a more or less injurious and even destructive effect on the lining of the mouth and stomach. Naturally, in such cases the introduction of any sort of instrument, even a soft rubber stomach tube, may result in a perforation in the weakened wall. In such conditions, rupture of the stomach may be caused by emesis. Poisons classified as irritants and neurotics generally have no special local or injurious action on the mouth and the stomach and therefore in such cases the stomach may be evacuated and washed with the aid of a stomach tube. In the absence of a stomach tube, emetics may be used without fear of injury.

In cases where there are no signs of injury to the lining of the mouth, the probabilities are that the poison is one of the irritants or neurotoxins; that is, the poison may be a salt of one of the poisonous metals, such as arsenic, mercury, or silver. It may be one of the crude drugs, such as opium, belladonna, or perhaps one of their many alkaloids, the most common of which are morphine, codeine, heroin, atropine, and strychnine.

 Emetics

There are many drugs that produce nausea and vomiting, but the number that may be used intentionally to cause a patient to vomit is relatively small. Vomiting may be stimulated by gagging or stroking the throat with the finger or a tongue depressor when the stomach is full of liquid. When an emetic is required, the following may be considered:

 Regulations and Responsibilities Pertaining to Controlled Substances, Alcohol, and Dangerous Drugs

Hospital corpsmen handling controlled substances and other drugs are held responsible for their proper distribution and custody. Nowhere is the demand for strict integrity more important. Misuse, abuse, loss, and theft of these substances has always, sooner or later, ended in tragedy and severe consequences. No one has ever profited by their misappropriation.

It behooves every hospital corpsman to thoroughly understand the responsibility concerning the custody and handling of controlled substances and other drugs and to be familiar with the regulations and laws pertaining to them.

Responsibility

Although MANMED, chapter 21, specifically assigns custodial responsibility for controlled substances, alcohol, and dangerous drugs to a commissioned officer and more specific control to the Nursing Service, you, as a hospital corpsman, are held responsible for:

  1. All controlled substances and other drugs entrusted to you.
  2. Their proper administration: the right drug at the right time to the right patient in the right way.
  3. Their proper security. All controlled substances and other drugs are to be kept under lock and key. Neither keys nor drugs are ever entrusted to a patient.

 Accountability

Hospital Corps personnel are held accountable for all quantities of drugs entrusted to them. Exercise great care to prevent the loss or unauthorized use of drugs. No drug will be administered without proper authority. In addition, U.S. Navy Regulations distinctly forbids the introduction, possession, use, sale, or other transfer of marijuana, narcotic substances, or other controlled substances.

 Drug Definitions

Although all drugs are to be treated with respect, certain groups require special handling and security measures. Controlled substances are those drugs listed in the Comprehensive Drug Abuse Prevention and Control Act of 1970, and alcohol. Schedules of controlled substances are established by this act. Products may migrate between schedules and new products may be added. These changes will be promulgated by the Navy Materiel Support Command in the Medical and Dental Materiel Bulletin.

Controlled drugs are controlled substances, plus any additional drug product designated for control by an appropriate military authority.

Accountable controlled substances and drugs are all items listed on schedules I, II, narcotic schedule III medications, non-narcotic schedule III medications, schedule IV and V, or other legend drugs that appropriate authority in the chain of command deem necessary for accountability procedures. The schedules of drugs will be discussed later.

 Manual of the Medical Department

For all intents and purposes, MANMED, chapter 21, directs precise measures to be taken to ensure the proper control and custody of controlled substances, controlled drugs, and accountable controlled substances and drugs. The Comprehensive Drug Abuse Prevention and Controlled Act of 1970 established five schedules dependent upon a drug's potential for abuse, medical usefulness, and degree of dependency, if abused. The following schedules are provided:

  1. Schedule I substances-Maximum abuse potential with little or no accepted medical usefulness (i.e., heroin, marijuana, LSD).
  2. Schedule II substances-High abuse potential and accepted medical usefulness; abuse leads to severe psychological or physical dependence (i.e., morphine, meperidine, amphetamines, pentobarbital). Prescriptions for any of these substances MAY NOT be refilled.
  3. Schedule III substances-Lesser degree of abuse potential with accepted medical usefulness; abuse leads to moderate dependence (i.e., paregoric, some barbiturates, Tylenol #3, Fiorinal). Prescriptions may be refilled up to five times within 6 months.
  4. Schedule IV substances-Low abuse potential with medical usefulness; limited dependence problems (i.e., diazepam, pentazocine, phenobarbital, chlordiazepoxide, flurazepam). Prescriptions of these may be refilled up to five times within a 6-month period.
  5. Schedule V substances-Low abuse potential, accepted medical usefulness, and limited dependence factors (i.e., Lomotil, ETH with Codeine). Prescriptions may be refilled up to five times within 6 months.

 Antidotes and Antidote Lockers

All persons in the Medical Department will be aware of the danger of poisons and the use of antidotes. A separate poison antidote locker marked "ANTIDOTE LOCKER" will be located prominently in every emergency room. If necessary, you may use more than one locker. In small ships with only one independent duty hospital corpsman aboard, the locker will be located immediately outside the emergency treatment room for ready accessibility when the corpsman is absent. Secure the locker with a seal. Whenever the seal is broken, the contents will be inventoried, the used antidotes replaced, and the locker resealed. Place an inventory list for each shelf on the inside of the door together with a copy of NAVMED P-5095, Poisons, Overdoses, and Antidotes, and the address and telephone number of the local poison control center.

All personnel involved in emergency room treatments will be thoroughly familiar with the contents of the locker and their use. The books, Clinical Toxicology of Commercial Products, by Gleason, Gosselin, Hodge, and Smith and Handbook of Poisons, by Robert H. Driesback, M.D. are recommended as reference material and should be outside the locker for easy reference. The list may be modified to meet local requirements; however, it is very important to keep each item up-to-date to avoid depletion or spoilage.

For further information, consult MANMED, chapter 21.

References

  1. NAVMED P-117, Manual of the Medical Department, chapter 21
  2. Drug Facts and Comparisons, 1985 ed. Philadelphia: J.B. Lippincott
  3. Goodman and Gilman's, The Pharmacological Basis of Therapeutics, ed 6. New York: The Macmillan Co.
  4. Physicians' Desk Reference, ed 37. New Jersey: Medical Economics Co, Inc.