Chapter 51. Principles of Pharmacology

pharmacognosy

(the study of characteristics of natural drugs and their sources).

pharmacotherapeutics

(the study of how drugs are used to treat disease).

toxicology

(the study of poisons or poisonous effects of drugs

pharmacokinetics

(the study of what the body does to drugs).

Chemical Development

A chemist conducts investigations that lead to the synthesis (chemical duplication) of one or more drugs, based on a natural substance's chemical properties. Some drugs are synthesized by strictly chemical methods. Others are duplicated by manipulating genetic information in a host organism. For example, human insulin is produced by these means, also known as recombinant deoxyribonucleic acid (DNA) techniques.

Controlled Substances

A controlled substance is a drug or drug product categorized as potentially dangerous and addictive. The greater the potential for abuse, the more severe the limitations on prescribing it. Federal laws strictly regulate use of these controlled drugs. States, municipalities, and institutions must adhere to these laws but may also impose their own regulations.

Recordkeeping

A physician who administers or dispenses (as opposed to prescribing) controlled drugs to patients must maintain two types of records: dispensing records and inventory records. Note that these requirements do not apply to physicians who prescribe drugs but who do not administer or dispense controlled drugs. Dispensing Records The dispensing record for Schedule II drugs must be kept separate from the patient's regular medical record. Each time a drug is administered or dispensed, the doctor must note the date, the patient's name and address, the drug, and the quantity dispensed. The dispensing record for drugs on Schedules III through V must include the same information. The record for these drugs may be kept in the patient's medical record unless the physician charges for the drugs dispensed. All dispensing records must be kept for 2 years and are subject to inspection by the DEA. Inventory Records A physician who regularly dispenses controlled drugs also must keep inventory records of all stock on hand. This regulation applies to all scheduled drugs. To take an inventory, count the amount of each drug on hand. Compare this amount with the amount of the drug ordered and the amount dispensed to patients. The controlled drug inventory must be repeated every 2 years. You must include copies of invoices from drug suppliers in the inventory record. All Schedule II drug inventories and records must be kept separate from other records. Inventories and records of other controlled drugs must be separate or easily retrievable from ordinary business and professional records. All records on controlled drugs must be retained for 2 years and made available for inspection and copying by DEA officials if requested. Disposing of Drugs If the doctor asks you to dispose of any outdated, noncontrolled drugs, you will most likely use the disposal company that takes your biohazardous waste. The DEA does not allow businesses to flush any medications and medications should not be placed in the trash. In some cases, you may work with a larger healthcare facility or pharmacy to ensure proper disposal so medications do not pollute the environment or end up in the trash where someone may take them. If the physician needs to dispose of controlled drugs, like expired samples, obtain DEA Form 41, called Registrants Inventory of Drugs Surrendered, which is available from the nearest DEA office or on the Internet. Complete the form in quadruplicate, have the doctor sign it, and call the DEA to obtain instructions for disposal of the drugs. If you must ship them, use registered mail. After the drugs have been destroyed, the DEA will issue the physician a receipt, which you should keep in a safe place. If physicians terminate their medical practice, they must return their DEA registration certificate and any unused copies of DEA Form 222 to the nearest DEA office. To prevent unauthorized use, write the word VOID across the front of these forms. Regional DEA offices will tell the physicians how to dispose of any remaining controlled drugs.

pharmacologist

A specialist in pharmacology

Vaccines

A vaccine is a special preparation made from microorganisms and administered to a person to produce reduced sensitivity to, or increased immunity to, an infectious disease. Vaccines are stored with the office supply of drugs and require similar handling. If you work in a pediatrician's office, you will handle the vaccines for childhood diseases. In an adult practice, you can expect to see influenza and pneumonia vaccines and vaccines for diseases to which patients might be exposed in foreign travel. It is important to know how vaccines work in the immune system. Through the immune system's action, a patient can be protected from—or made not susceptible to—a disease. This immunity results from the formation of antibodies that destroy or alter disease-causing agents. You should review information about immunity discussed in The Lymphatic and Immune Systems chapter.

Prescriptions

Any drug not available over the counter requires a prescription. As a medical assistant, you should be able to interpret a prescription in order to discuss it with the patient, authorized prescriber, or pharmacist. You must become familiar with the doctor's style of writing or the electronic prescription process at your facility.

Nonpharmacologic Pain Management

Because of drug interactions, adverse effects, or the risk of dependence, many patients may either prefer not to or should not take drugs to relieve chronic pain. The overuse and abuse of pain medications can be a problem for patients. Pain frequently motivates these patients to use complementary and alternative medicine (CAM). Some examples include Chiropractors use spinal adjustments to treat chronic back or neck pain. Massage is used to treat headache or arthritis and to promote healing through relaxation. An acupuncture procedure in which very small amounts of electrical current are applied through needles has been used successfully to block the pain of surgery without anesthesia. Yoga uses postures to exercise the spine and stimulate the lymphatic system, helping to remove from the body toxins that may cause pain and stiffness in muscles and joints. Meditation is said to balance a person's physical, emotional, and mental states and is used as an aid in treating stress, anxiety, and pain. Hypnotism may be used to help patients overcome pain caused by stress-induced migraine headaches. Glucosamine chondroitin, a dietary supplement, is taken to treat osteoarthritis by reducing pain and slowing down joint cartilage damage. Magnetic therapy involves the use of magnets of varying sizes and strengths placed on the body to relieve pain or treat disease. Biofeedback can help a patient learn to evoke relaxation, which helps block pain perception. CAM approaches and therapies have become more common in recent years. Some physicians and patients are seeking agents and treatments to manage health problems, like chronic pain, that are less expensive, have fewer side effects, and are more accessible than traditional medical interventions. Pain clinics that use multiple pain management techniques are common.

The FDA and CAM Therapies

Complementary and alternative therapies such as dietary supplements, herbal products, and the use of other natural but as yet scientifically unproven therapies are increasing in use. Many physicians prescribe these therapies and even more patients take them on their own with success. There is one important difference between dietary supplements and medications. Medications must meet approval of the FDA prior to being marketed and sold. Drug manufacturers must provide scientific documentation of the effectiveness of a drug before it can be marketed. On the other hand, manufacturers of dietary supplements do not have to provide evidence of effectiveness or safety. Of course, they are not permitted to market or sell a product that is proven unsafe. However, once a supplement is marketed, the FDA must prove that the product is not safe to have it taken from the market. Additionally, dietary supplements are not standardized between batches or among manufacturers. Standardization is a process that ensures the consistency and quality of each batch of supplement produced. Thus, the amount and quality of a dietary supplement may differ between batches by one manufacturer or between the same supplement made by two different manufacturers. FDA-approved medications must be standardized and will always be consistent between batches and manufacturers. The FDA does require that certain information appear on dietary supplement labels. Dietary supplements may include claims on their labels that describe the effect of a substance in maintaining the body's normal structure or function. For example, a label might state, "Promotes healthy joints and bones." The FDA does not review or authorize this claim, so the manufacturer is required to also place a disclaimer on the product. This disclaimer is a statement indicating that the claims have not been evaluated by the FDA. For example, the disclaimer for the claim above would be: "This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent disease." Figure 51-4 shows an example of a label that meets the FDA's labeling requirements.

Doctor Registration and Drug Ordering

Doctors who administer, dispense, or prescribe any controlled substance must register with the DEA and have a current state license to practice medicine and, if required, a state controlled substance license. They also must comply with all aspects of the CSA. This includes registration, renewal, and ordering of controlled substances, as outlined in Procedure 51-1, at the end of this chapter.

Drug Security

Drugs that are controlled substances must be kept in a locked cabinet or safe. If required by state law, use double locks for opioids. The physician or other licensed practitioner should keep the key(s) at all times, except when asking you to add to or take from the stock (if this is a task medical assistants are permitted to perform in your state). If controlled drugs are stolen from the physician's office, call the regional DEA office at once. Also, notify the state bureau of narcotic enforcement and the local police. File all reports required by the DEA and other agencies as a follow-up.

Epocrates®

Epocrates® is a software program that can be loaded on to a smartphone or other personal digital assistant. Epocrates® includes more than 3,300 brand and generic drugs, alternative medicines, a drug-drug interaction checker, an IV compatibility checker, health insurance Medicare Part D formularies, and an infectious disease treatment guide

Sources of Drug Information

Having access to up-to-date and credible sources of drug information in the office for when you or the physician need detailed information about a specific drug is essential. The most up-to-date resources are found online or through smartphone or other electronic applications. Books are available, but resource books are also available online. The Physicians' Desk Reference (Figure 51-5), United States Pharmacopeia/National Formulary, American Hospital Formulary Service (AHFS®), and Epocrates® are credible sources of drug information. Package inserts and drug labels are also valuable drug information sources.

Natural Products

Most often, drugs originate as substances from natural products, such as plants, animals, minerals, bacteria, or fungi. For hundreds of years, drugs have been made from seeds, bulbs, roots, stems, buds, leaves, or other parts of plants. Two examples of plant-derived drugs are digitoxin, which comes from the foxglove plant (see Figure 51-2), and quinine, which comes from cinchona tree bark. Digitoxin is used to treat heart failure and abnormal heart beats. Quinine is used to treat malaria. Animals also are used as a source of drugs. Certain animal substances have been shown to be compatible with human physiology. Some examples of animal substances used as drugs include glandular substances, such as insulin and thyroid hormones; fats and oils, such as cod-liver oil; enzymes, such as pancreatin and pepsin; and antiserums and antitoxins for vaccines. Mineral sources yield various substances that can be used as they occur naturally or mixed with other substances. Two drugs derived from mineral sources are potassium chloride and mineral oil. Simple organisms, like bacteria and fungi, produce substances that are used to make certain antibiotics, such as cephalosporins and penicillins (see Figure 51-3).

E-Prescribing

On July 15, 2008, Congress enacted the Medicare Improvements for Patients and Providers Act of 2008 (MIPPA) and it became law. MIPPA provides positive incentives for practitioners who use electronic prescribing in 2009 through 2013. E-prescribing is intended to bring greater safety to patients by providing for automatic drug and allergy interaction checking and the elimination of medication errors due to poor handwriting. E-prescribing also is designed to bring a greater efficiency to the prescribing process for providers, as it dramatically decreases communication from pharmacies requesting prescription clarifications. Surescripts is the national clearinghouse for e-prescribing. The company electronically connects physicians, pharmacists, and payers nationwide, enabling them to exchange health information and prescribe without paper. Surescripts collaborates with national EHR vendors, pharmacies, and health plans to support physicians using EHR software. With this network in place, healthcare providers can electronically access prescription information from pharmacies, health plans, and other providers to see the patient's total prescription history from all sources. Through e-prescribing, EHRs are providing meaningful improvements in cost, quality, and patient safety. For example, when a medication is taken off the market, a record of all patients who have been prescribed this medication can be queried electronically and the physicians and patients notified of the change.

Drug Names and Categories

One drug may have several different names, including the drug's official name (also known as the generic name), international nonproprietary name, chemical name, and trade name (brand or proprietary name). To demonstrate, the trade name antibacterial drug prescribed by physicians as Keflex® or Biocef is also identified by the following names: Cephalexin (generic name) Cefalexin (international nonproprietary name) 7-(D-a-amino-a-phenylacetamido)-3-methyl-3-cephem-4-carboxylic acid monohydrate (chemical name) As a medical assistant, you will probably need to use only generic and trade names. In general, think of the generic name of a drug as a simple form of its chemical name. For each new drug marketed by a drug manufacturer, the United States Adopted Names (USAN) Council selects a generic name. This name is nonproprietary, meaning it does not belong to any one manufacturer. A generic name is also considered a drug's official name, which is listed in the United States Pharmacopeia/National Formulary. A drug's manufacturer selects the drug's trade name, which is protected by copyright and is the property of the manufacturer. When a new drug enters the market, its manufacturer has a patent on that drug, which means that no other manufacturer can make or sell the drug for 17 years. When the patent runs out, any manufacturer can sell the drug under the generic name or a different trade name. The original manufacturer, however, is the only one allowed to use the drug's original trade name. For example, the antibiotic cephalexin has two trade names, Keflex® and Biocef. Different manufacturers own these names. A physician may prescribe a drug by its generic or trade name. Because generic drugs are usually less expensive, most physicians try to prescribe them if possible. Many states allow pharmacists to substitute a generic drug for a trade name drug unless the physician specifies otherwise. In fact, most health insurance prescription plans now require the substitution of generic drugs for trade name drugs (unless otherwise specified by a physician). Frequently, they also require the pharmacy to charge a higher copay amount for trade name drugs than for generic drugs. Some prescription plans now offer a mail-in pharmacy through which a patient can obtain generic drugs with a reduced copayment or without any copayment. Drugs are categorized by their action on the body, general therapeutic effect, or the body system affected. Table 51-1 lists a variety of drug categories, their actions, and common drugs, including drugs from the top 200 drugs most commonly prescribed in the year 2010.

Pharmacodynamics

Pharmacodynamics is the study of the mechanism of action, or how the drug works to produce a therapeutic effect. Drugs are placed in categories based on their mechanism of action. Pharmacodynamics includes the interaction between the drug and target cells or tissues and the body's response to that interaction. For example, when a patient with diabetes takes insulin, the drug acts by allowing the movement of glucose across cell membranes. This movement makes the glucose available to cells to use as an energy source. The end result is a decrease in the blood glucose level.

Pharmacokinetics

Pharmacokinetics is what the body does to a drug—that is, how the body absorbs, distributes, metabolizes, and excretes the drug. It is important to understand these processes so you will be able to explain to patients the reasons for taking a particular drug with food or for drinking plenty of water while taking a drug. These four processes can be remembered by using the acronym ADME: Absorption-Distribution-Metabolism-Elimination. Absorption Absorption is the process of converting a drug from its dose form, like a tablet or capsule, into a form the body can use. For example, tablets or capsules are absorbed through the stomach or intestines into the bloodstream. Water, food, or a particular food may either hinder or assist the absorption of a specific drug through the stomach or intestines. Some drugs may irritate the digestive organs if they are taken without food or water. Because of such possible reactions, patients must precisely follow instructions for taking a drug with plenty of water, with food, or without food. Injected drugs are absorbed through the skin (intradermally), through the tissue just beneath the skin (subcutaneously), or through muscle (intramuscularly), depending on the method of injection. Absorption allows the drug to enter the bloodstream and pass into tissues. The extent and rate of drug absorption depend on several factors, including the route of administration. When the drug is administered by mouth, for example, coatings on tablets or capsules and the amount and type of food consumed with the drug may affect absorption. Drugs administered intravenously do not require absorption; they are directly available to target cells from the bloodstream. Distribution Distribution is the process of transporting a drug from its administration site, such as the muscle of an injection site, to its site of action. Distribution also pertains to the length of time a drug takes to achieve maximum or peak plasma levels; that is, the length of time between dosing and availability in the bloodstream. Metabolism Drug metabolism is the process by which drug molecules are transformed into simpler products called metabolites. This transformation usually occurs in the liver, where enzymes break down the drug. Some drugs, however, are metabolized in the kidneys. Metabolism can be affected by disease, a patient's age or genetic makeup, a drug's characteristics, or other factors. When drugs metabolized in the liver are prescribed for either children or the elderly, the dose is likely to be lower than that prescribed for young adults. Metabolism in children and the elderly is different from metabolism in other patients; the drugs may remain in the body longer and possibly reach harmful levels. The same concern holds true for any patient with impaired liver or kidney function if prescribed drugs are metabolized in the affected organ. Excretion Excretion describes the manner in which a drug is eliminated from the body. Most drugs are eliminated in urine. Drugs also may be excreted in feces, perspiration, saliva, bile, exhaled air, and breast milk.

Pharmacotherapeutics

Pharmacotherapeutics is the study of how drugs are used to treat disease. This area of pharmacology is sometimes called clinical pharmacology. Pharmacotherapeutics includes topics such as drug categories (discussed in the next section), drug indications and labeling, safety, efficacy (therapeutic value), and kinds of therapy. Page 1045 Indications and Labeling An indication is the purpose or reason for using a drug. The Food and Drug Administration (FDA) must approve indications before they can become part of a drug's labeling. The FDA is an agency of the Department of Health and Human Services. It regulates the manufacture and distribution of every drug used in the United States. Labeling also includes the form of the drug, such as tablet or liquid. Regardless of category, some drugs may be used to treat several different conditions. Multiple uses are possible if the drug affects several body systems at once or if the drug's primary effect produces significant secondary effects in other body systems. When a drug is used for multiple indications, one or more indications may not be in its labeling. Off-label prescribing is legal. For example, Benadryl (diphenhydramine) is an antihistamine used to treat allergic symptoms in both children and adults. Because it tends to make a patient sleepy but is safe for children, a pediatrician may use a low dose of Benadryl as a temporary sedative for a young child. Its use as a sedative, however, is not part of the labeling for Benadryl. Another example of a drug with multiple uses is minoxidil. As a trade-name tablet, it is known as the antihypertensive Loniten®; as a trade-name topical solution, it is known as the hair-growth stimulant Rogaine®. In the case of minoxidil, both indications are approved, but the tablet labeling is for hypertension and the topical solution labeling is for hair growth. It is important to be aware of these labeling considerations when dealing with questions from patients. Never assume a drug is appropriate for only one use or administered in only one form. Always consult the physician or other approved source of drug information before answering a patient's question. Safety The safety of a drug is determined by how many and what kinds of adverse effects are associated with it. Some adverse effects are common, whereas others are rare. An adverse effect may require immediate attention. It is not uncommon for a patient to call the physician's office with complaints of new symptoms soon after beginning therapy with a drug. Be alert for such complaints because they could be signs of an adverse reaction to the drug or an interaction with another medication. These calls should be brought to the physician's attention. Efficacy A patient may complain that a newly prescribed drug is not doing what the doctor said it would. There are a variety of possible explanations for such a complaint, including The drug is working adequately, but the patient does not understand how it works. The dosage (size, frequency, and number of doses) needs to be adjusted. The patient is not taking the medication according to the directions. The drug has not yet reached a therapeutic level in the bloodstream. The wrong drug was prescribed, or the wrong drug was dispensed by the pharmacy (this is rare, but possible). Some drugs work better in some patients than in others; not every drug is for everyone (this is particularly true of antihistamines). Some forms of a drug work better than others, such as tablets versus injection. The generic drug does not work, but the trade name drug does. Kinds of Therapy There are several descriptive terms for drug therapy. Depending on a patient's condition, the physician may use drugs for any of the following kinds of therapy: Acute: Drug is prescribed to improve a life-threatening or serious condition, such as epinephrine for severe allergic reaction. Empiric: Drug is prescribed according to experience or observation until blood or other tests prove another therapy to be appropriate, such as penicillin for suspected strep throat. Maintenance: Drug is prescribed to maintain a condition of health, especially in chronic disease, such as an anti-inflammatory medication for inflammatory bowel disease. Palliative: Drug is prescribed to reduce the severity of a condition or its accompanying pain, such as morphine for cancer. Prophylactic: Drug is prescribed to prevent a disease or condition, such as immunizations or birth control drugs. Replacement: Drug is prescribed to provide chemicals otherwise missing in a patient, such as hormone replacement therapy for a woman in menopause. Supportive: Drug is prescribed for a condition other than the primary disease until that disease resolves, such as a corticosteroid for severe allergic reactions. Supplemental: Drug or nutrients are prescribed to avoid deficiency, such as iron for a woman who is pregnant.

Interpreting a Prescription

Prescriptions for new or renewed medications are completed or approved by the physician. A prescription has specific parts that must be present before it can be filled or renewed (Figure 51-9). The basic components of a prescription are Prescriber information: Name, address, telephone number, and other information identifying the prescriber. Patient information: Date, patient's full name, date of birth, address, and other information to identify the patient. Medication prescribed: Includes generic or brand name, strength, and quantity. This is sometimes called the inscription and is found after the Rx. Subscription: Instructions to the pharmacist dispensing the medication. This may include generic substitution and refill authorization. Signa: Also known as the transcription; refers to patient instructions. These instructions generally follow the abbreviation Sig, which means mark. Signature: Prescriber's signature for handwritten prescriptions. The prescriber's signature must be in ink, but it cannot be a stamped signature. A digital signature is used if it is secure; otherwise, the prescription must be printed and then signed or otherwise authorized. DEA number: This is required for prescriptions of Schedules II, III, IV, and V medications only. Page 1055 Many terms and abbreviations are used in prescriptions. See Table 51-4 for examples. Abbreviations for drug names should not be used because there are similar abbreviations for multiple drugs. Certain other abbreviations are not to be used, as discussed in the Patient Interview and History chapter, because they tend to cause errors. A medical assistant must be able to interpret a prescription with accuracy. Refer to Procedure 51-2, Interpreting a Prescription, at the end of this chapter. Managing Prescriptions Prescriptions may be printed or handwritten on a prescription blank. They also may be entered electronically and printed, or entered electronically and transmitted directly to a pharmacy. When the information is entered electronically and transmitted directly, this is known as e-prescribing. With e-prescribing, the medication information is received at the pharmacy and the actual prescription is never in the patient's hands. This is the most secure and efficient way for prescriptions to be completed. See Points on Practice: E-Prescribing. In rare cases, preprinted prescription blanks are used that include the physician's name, address, telephone number, state license number, and DEA registration number plus blank space for writing the patient's name and address, the date, and other information. To prevent unauthorized use of prescription blanks, never leave them unattended. Most frequently, prescriptions are entered into an EHR, then printed and signed for patients to take with them to the pharmacy. If something about a prescription arouses suspicion, the pharmacist who receives a prescription may call the physician's office to verify it. You should be able to check the patient's records and tell the pharmacist whether the doctor wrote a prescription for that patient. If the prescription is a forgery, notify the physician and, if she gives you authorization, notify the DEA. Page 1057 Telephone Prescriptions If requested by the physician, you may telephone a new or renewal prescription to the patient's pharmacy. You may not, however, telephone a prescription for a Schedule II drug. In an emergency situation, when a patient needs a drug immediately and no alternative is available, the doctor may telephone a prescription for a Schedule II drug. The amount must be limited to the period of emergency and a written prescription must be sent to the pharmacist within 72 hours. The pharmacist must notify the DEA if a written prescription does not arrive within the specified time. Patient requests for prescription renewals occur daily. The renewal requests may be called in to the receptionist or left on a designated phone or mail system. It is the medical assistant's responsibility, if asked, to handle the prescription renewals/refills in an appropriate manner.

Immunizations

The Advisory Committee on Immunization Practices, the American Academy of Pediatrics, and the American Academy of Family Physicians jointly publish immunization schedules, which are found in the Assisting in Pediatrics chapter. These schedules cover children from infancy through 18 years of age. Just as children receive immunizations before exposure to disease, adults may receive immunizations for influenza, pneumonia, or other diseases, including those to which an adult could be exposed during travel. Figure 51-10 displays the adult immunization schedule. Patients are sometimes immunized after exposure. For example, if patients have been exposed to a serious disease and there is too little time for them to produce antibodies, they may receive an antiserum containing antibodies to the disease-carrying organism. These immunizations are made from human or animal serum. If bacterial toxins (rather than bacteria) cause the disease, the patient may receive an antitoxin. Antiserums and antitoxins must be used cautiously and are usually reserved for life-threatening infectious diseases. Because patients can be allergic to substances in animal antiserums and antitoxins, human serums are usually preferred. An example of a post-exposure immunization is one given to a patient who has been exposed to hepatitis B virus (HBV). This patient should be given the antiserum hepatitis B immune globulin (HBV-Ig) within 7 days after exposure and again 28 to 30 days later. Because HBV-Ig is made from human serum, it causes relatively few adverse reactions. Another example involves a patient who may have been exposed to tetanus (lockjaw) organisms as the result of an injury like a puncture wound. This patient may receive tetanus immune globulin (T-Ig, a human product) or tetanus antitoxin. Because tetanus antitoxin is made from horse serum, it may cause serious reactions in patients who are allergic to horses or horsehair. For every vaccine in your medical office, you must be familiar with the indications, contraindications, dosages, administration routes, potential adverse effects, and methods of storage and handling. You must carefully read the package insert provided with each vaccine and, when necessary, consult drug reference books for further information. Knowledge of correct administration techniques is required and will be discussed in the Medication Administration chapter.

American Hospital Formulary Service (AHFS®)

The American Society of Hospital Pharmacists in Bethesda, Maryland, publishes the American Hospital Formulary Service, or AHFS®. It sells the two-volume set by subscription and provides four to six supplements each year. The AHFS lists generic names and is divided into sections based on drug actions. The AHFS® is also available online.

Controlled Substance Labeling

The CSA also set up a labeling system to identify controlled substances. An example of this label is shown in Figure 51-8. The large C means the drug is a controlled substance and the Roman numeral inside the C corresponds to the drug's DEA schedule.

Comprehensive Drug Abuse Prevention and Control Act

The Comprehensive Drug Abuse Prevention and Control Act, also known as the Controlled Substances Act (CSA) of 1970, is the federal law that created the DEA and strengthened drug enforcement authority. The CSA designates five schedules, according to degree of potential for a substance to be abused or used for a nontherapeutic effect. Schedule I drugs do not have a medical use. Schedule II drugs include opioids, which are natural or synthetic drugs that produce opium-like effects. Examples of Schedule II drugs include codeine, morphine, and meperidine (Demerol®). Government agencies use the popular term narcotics for opioids. Sometimes the DEA reclassifies drugs. For example, a Schedule III drug may eventually be found to be less addictive than originally determined and therefore reclassified as a Schedule IV drug. The five schedules and examples of substances in each are outlined in Table 51-3.

FDA Regulation and Drugs

The Food and Drug Administration (FDA) requires that drug manufacturers perform clinical tests on new drugs before humans use the drugs. These tests include toxicity tests in laboratory animals, followed by clinical studies (clinical trials) in controlled groups of volunteers. Some volunteers are patients; others are healthy subjects. Clinical tests are designed to consider the ratio of benefits to the risk of adverse side effects. If the clinical tests prove the drug is safe and effective, the FDA approves it for marketing. The manufacturer must continue to demonstrate the drug's safety and efficacy and must submit reports whenever it discovers unexpected adverse reactions. The FDA can withdraw a drug from the market at any time if evidence suggests it is no longer safe or effective. This is known as a recall. The FDA also regulates drug manufacturing. It ensures that drugs shipped between states have the proper identity, strength, purity, and quality. Each manufacturer must consistently identify each drug by a particular color, form, shape, size, and label. It must produce every dose at the same tested strength, using the exact formula approved by the FDA. The manufacturer also must use high-quality, contaminant-free ingredients. The FDA regulates all drugs in one way or another, including over-the-counter, prescription, and even complementary and alternative therapies (CAM). See Points on Practice: The FDA and CAM Therapies. Over-the-Counter Drugs A nonprescription, or over-the-counter (OTC), drug is one the FDA has approved for use without a licensed healthcare practitioner's supervision. The consumer must follow the manufacturer's directions to use the drug safely. Some drugs, like aspirin and vitamin supplements, have been OTC drugs for many years. The number of prescription drugs granted OTC status is increasing. Although OTC drugs are safe when used as directed on the package, patient education contributes significantly to their safe use. Page 1048 Prescription Drugs A prescription drug is one that can be used only by order of a physician and must be dispensed by a licensed healthcare professional, such as a pharmacist, physician, podiatrist, or licensed midwife. Some prescription drugs are dispensed as OTC medications at much lower strengths. Pregnancy Categories Because clinical trials are not typically done on pregnant women, most of the data about the effect of medications on pregnant women is obtained after FDA approval. Some drugs can cause physical defects to the fetus if the mother takes them during pregnancy, especially during the first trimester. To assist physicians who are prescribing medications for pregnant women, the FDA has created the categories A, B, C, D, and X based upon the degree to which available information has ruled out risk to the fetus. See Table 51-2. Most medications are typically Category C, although a medication can change categories after approval based upon adverse reactions. Also, some medications are placed into different categories based upon the trimester of the pregnancy.

Physicians' Desk Reference (PDR)

The Physicians' Desk Reference®, or PDR, is published annually, along with supplements twice a year. It is sent free to doctors' offices and sold through bookstores. PDR Network, the company that publishes the PDR, also publishes separate editions for generic, nonprescription, and ophthalmologic drugs, as well as a guide to drug interactions, adverse effects, and indications. It is also available online. The PDR presents information provided by pharmaceutical companies about more than 2500 prescription drugs. It has the following sections: Section 1—Manufacturer's index (color-coded white), which includes the pharmaceutical company's name, address, emergency telephone number, and available products. Section 2—Brand- and generic-name index (color-coded pink). Section 3—Product category index (color-coded blue). Section 4—Product identification guide with full-color photos of more than 2400 actual medications. Section 5—Product information. Section 6—Diagnostic product information. The product information section is divided according to manufacturer, and the drugs are then grouped alphabetically within each manufacturer's subsection. The information is provided for the PDR by the manufacturer and is either the drug package insert or a similar document. After the large product information section, various smaller other sections are provided, which include diagnostic product information, state drug information centers, ratings for drug use in pregnancy, a state DEA directory, state-aided drug-assistance programs, patient assistance programs, drugs that should not be crushed, dosing instructions in Spanish, and the system for reporting adverse reactions to medications. All of these plus the PDR Internet site and PDR electronic library that come with the PDR are important resources for drug information.

United States Pharmacopeia/National Formulary

The United States Pharmacopeia/National Formulary, or USP-NF, is the official source of drug standards in the United States, published about every 5 years. As the official public standards-setting authority for all prescription medications, OTC drugs, dietary supplements, and other healthcare products, by law, every product sold under a name listed in the USP-NF must meet the USP's strict standards. The USP-NF describes each product approved by the federal government and lists its standards for purity, composition, and strength as well as its uses, dosages, and storage. The NF portion of the book provides the chemical formulas of the drugs. The USP-NF is available online.

Package Insert

The package insert for each drug describes the drug, its purpose and effects (clinical pharmacology), indications, contraindications (conditions under which the drug should not be administered), warnings, precautions, adverse reactions, drug abuse and dependence, overdosage, dosage and administration, and how the drug is supplied (for example, tablets in different doses, or liquid). The package insert, whether it is part of the PDR or found in the medication package, is a valuable resource for drug information. See Figure 51-6.

Drug Labels

To prepare and administer drugs, you must understand information that appears on drug labels, including the drug name, form, dosage strength, total amount in the container, route of administration, warnings, storage requirements, and manufacturing information. See Figure 51-7. By law, the generic name, as determined by the USP-NF, must appear on the drug's label. The drug label also may include the trade (brand) name used to market the drug. The trade name is typically indicated by a registered trademark symbol ®. The form of the drug is included, such as a tablet, capsule, liquid for oral administration or an injection. Drug labels include information about the amount of the drug present. This amount, combined with information about the form of the drug, identifies the drug's dosage strength. On the label, the dosage strength is stated as the amount of drug per dosage unit. In most cases, the amount of the drug is listed in grams (g), milligrams (mg), or micrograms (mcg). In some cases, a drug may be a combination drug, meaning more than one drug is included. If a container holds more than one dose of medication, then the total number or volume of medication is listed on the label. The label also should include the route of administration, especially if it is a liquid. Warnings, such as "May be habit forming," are included, as well as storage information. Storage information indicates the specific conditions under which a medication must be stored. Manufacturer's information is always included. Information about how to mix or reconstitute a medication also may be found on the medication label.

Toxicology

Toxicology is the study of the poisonous effects, or toxicity, of drugs, including adverse effects and drug interactions. In addition to immediate toxic effects that can occur when drugs are administered, you must be aware of some possible toxic effects that may not be apparent right away: An adverse effect on a fetus when the drug crosses the placenta. An adverse effect on infants when the drug passes easily into breast milk. Adverse reactions reported in clinical trials, such as headache, drowsiness, gastric upset, or other effects. An adverse effect in immunocompromised patients who are unable to metabolize a drug normally. An adverse effect in pediatric or elderly patients or in patients with hypertension, diabetes mellitus, or other serious chronic conditions. Page 1046 An adverse drug interaction when the drug is taken with another drug or food that is incompatible. A carcinogenic (cancer-causing) effect in some patients. Nearly always, an adverse effect is encountered during the clinical trials of a drug, and there will be mention of the adverse effect under that heading in the package insert or in accepted drug reference works. In the reports of clinical trials, the drug company must report all adverse effects noted during testing. As a result, effects that, at least theoretically, could be caused by the drug are included. In dealing with patients who are about to begin drug therapy, use discretion when mentioning specific adverse effects associated with drugs. The patient must be informed; however, you do not want to cause undue alarm or discourage patients from taking the needed medication. Always ask patients if they have any questions and have the doctor answer patients' drug-related questions. Because patients will receive lists of adverse effects from the pharmacist, encourage them to discuss concerns with the pharmacist or to call the doctor's office. Also encourage patients to inform the doctor of adverse effects they experience after beginning drug therapy.

pharmacology

drug is a chemical compound used to prevent, diagnose, or treat a disease or other abnormal condition. The study of drugs

Antibody Formation

he human body creates antibodies in response to an invasion by an antigen (foreign substance). When an antigen enters the body, specialized white blood cells (lymphocytes) produce antibodies, which in turn combine with the antigens to neutralize them. This action arrests or prevents the reaction or disease the antigen otherwise would cause. Specific antibodies always fight specific antigens. Antigens can be bacteria, viruses, or other organisms that enter the body in spite of its natural defenses. Toxins, pollens, and drugs also can be antigens if the body reacts to them by forming antibodies. (Allergens are antigens that induce an allergic reaction.) Vaccines contain organisms that have been killed or attenuated (weakened) in a laboratory. Because the organisms have been weakened, they stimulate antibody formation but do not overpower the body and cause disease. They may, however, still be strong enough to cause a fever and slight inflammation at the injection site. Some vaccines, like those for influenza, may even produce some of the lesser effects of the disease against which they provide protection. Immunizations made from organisms are called vaccines. Those made from the toxins of organisms are called toxoids. Some immunizations, such as the polio vaccine, last a lifetime. Others, like tetanus toxoid, do not. In the latter case, booster immunizations must be used to stimulate the lymphocytes to produce antibodies again.

pharmacodynamics

the study of what drugs do to the body)