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CHAPTER
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5
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Pharmacotherapeutics
MAry C. BruCker
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TekOA L. kIng
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overview that includes discussion of specific situa-
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Introduction
tions such as common drugs used for treating woman
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Throughout history, pregnancy and midwifery have who are pregnant or breastfeeding. Although many
been surrounded in myths. One of the modern myths examples are included in the chapter as illustrations,
is that midwives eschew the use of drugs and only it should not be assumed that they are exhaustive.
use, at most, herbal remedies. In reality, knowledge Additionally, certain terms—including “drugs,”
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of pharmacology is necessary for the practice of mid- “agents,” “medications,” and “pharmaceuticals”—
wifery in the twenty-first century so that midwives are used interchangeably throughout the chapter. The
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use pharmacotherapeutic agents appropriately. All word “drug” does not connote an illicit substance
50 states grant some type of prescriptive authority or a licit substance being abused; rather, drugs with
1 abuse potential are specifically designated as such.
to certified nurse-midwives. Prescriptive author-
ity remains less common for certified midwives, as Drugs are listed by generic name followed by the
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their credential is newer and their numbers fewer. most common brand name in parentheses.
Prescriptive authority is controlled on the state level This chapter has four sections. The first reviews
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and ranges from very limited to relatively broad. fundamental concepts for midwives with prescriptive
Many states limit prescriptive authority according to authority, including the drug development process,
the schedule of controlled substances described later legal requirements for prescriptive authority, and
in this chapter. Some prescriptive authority laws are essential information about drug–drug interactions
based on specific wording in state licensing laws or and adverse effects of drugs. The second section re-
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practice sites. views essential drug categories most commonly used
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As an increasing number of midwives attain in midwifery practice. The third and fourth sec-
prescriptive privileges, knowledge of pharmacology tions describe pharmacologic essentials specific to
1 prescribing drugs for women who are pregnant and
becomes even more important. Although midwives
may use a wide repertoire of nonpharmaceutical tech- women who are lactating.
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niques, there are conditions and situations in which
no effective substitutes exist for pharmacologic treat-
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ments. One of the greatest challenges to the midwife The Lexicon of Pharmacology
in clinical practice is maintaining current informa-
tion about drug indications, doses, side effects, and As knowledge in pharmacology has expanded, so
contraindications. has the accompanying lexicon. A prerequisite to
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Throughout this text, specific therapeutic agents understanding drug actions and their effects is the
are discussed as treatments for various conditions. midwife’s ability to define the various terms used in
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However, the field of pharmacology is both expansive pharmacology. Some of these terms are old and es-
and ever-changing; thus this chapter presents a wide tablished. Pharmacology itself means the study of all
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1
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2 PART II Primary Care
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aspects of drugs. In addition, several more specific drug (e.g., an acid) or by pharmacotherapeutic indi-
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terms are employed in the field. Pharmacokinetics cation (e.g., sedative). The same drug could be identi-
describes the absorption, distribution, metabolism fied by its chemical name [e.g., 2-(2-methyl-5-nitro
(biotransformation), and excretion (clearance) of 1H-imidazol1-l-yl)ethanol], its generic name (metro-
drugs. These factors then determine the amount nidazole), and its most common brand name (Flagyl).
of the agent available at the target sites for action. Drugs formulated as medications are regu-
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Pharmacodynamics refers to the action of drugs on lated in the united States by the Food and Drug
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the body. The pharmacodynamic action of a drug Administration (FDA), one of 12 agencies within the
results from the drug’s binding relationship at the u.S. Department of Health and Human Services. The
receptor site as either an agonist or an antagonist. pharmaceuticals for which the FDA has authority
Pharmacotherapeutics is the field focusing on treat- may be obtained by prescription or over the counter.
ment effects of drugs. Additional terms can be found The FDA also regulates medical devices such as
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in the pharmacology glossary presented in Box 5-1. intrauterine contraceptive systems (e.g., Paragard,
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Mirena) and biologic agents such as vaccines. The
FDA does not regulate dietary supplements, such as
Drugs in Modern Society St. John’s wort, although the agency does track ad-
verse reactions that occur following use of dietary
supplements. Similarly, the FDA may require labeling
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More than 4 billion prescriptions are written each to designate that safety has not been established for
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year in the united States. each prescription filled can cosmetics, although recall of cosmetics is voluntary
result in a 20% profit to the manufacturer, making by the manufacturer.5
the pharmaceutical industry highly profitable. Drugs that are approved for specific use by the
Most adults in the united States take at least FDA must demonstrate both safety and efficacy for
one medication, and many take multiple pharma- that indication in a series of preapproval studies that
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ceuticals daily. The extensive use of drugs is related are submitted to the FDA for review. The regula-
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to several factors: the increase in their availability; tion of drugs is administered by the Center for Drug
the public belief that drugs are safe, especially over- evaluation and research (CDer), a subgroup within
the-counter products; and the plethora of healthcare the FDA that oversees the research, development,
providers, pharmacies, and Internet sites that supply manufacture, and marketing of both prescription
drugs. These multiple options mean that an indi- and over-the-counter (OTC) drugs. After FDA ap-
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vidual may receive drug prescriptions and recom- proval, if unexpected risks are detected, CDer takes
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mendations from a variety of providers who may be action to inform the public, change a drug’s label, or,
unaware of the other prescribers’ actions. Direct-to- when necessary, remove the product from the mar-
customer advertising exposes many more individu- ket. The FDA itself does not develop, manufacture,
als to prescription drugs and proposed therapeutic or test drugs.
options of which they might have been previously Drug manufacturers submit full reports of stud-
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unaware.3 In addition to public acceptance of drugs ies conducted on specific drugs, called clinical trials,
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to treat illnesses, there is a growing appreciation of so that CDer can evaluate the data and determine if
how agents may be used for prophylaxis against the drug should be approved for a specific indication.
various diseases or for general health maintenance. This approval commonly is termed FDA labeling.
Drugs used for prophylaxis tend to be used for long The clinical trials are intended to be appropriately
periods of time. They include blockbuster drugs, large enough to determine safety and effectiveness.
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such as atorvastatin (Lipitor). However, sometimes the FDA approves a drug, only
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even individuals who avoid taking specific drugs to remove it from the marketplace later due to ad-
or agents may constantly be exposed to pharmaceu- verse effects that emerge once the drug is in use by a
ticals through the food chain or in their daily envi- large diverse population or when used in conjunction
4
ronment. The results of such exposure, including with other agents. Box 5-2 identifies the sequenc-
direct toxic reactions and reproductive toxicology, ing of studies and subsequent clinical trials that are
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are beyond the scope of this chapter, although this conducted prior to FDA approval, and Figure 5-1
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area is likely to grow in importance. illustrates the process.6
Historically, women have not been participants
Drug Development and Regulation 7,8
in most drug development studies. Although there
Drugs are labeled in various ways. Specific drugs can are many reasons for this exclusion, one factor is
be described by the physiochemical property of the the changing environment in a woman’s body over
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CHAPTER 5 Pharmacotherapeutics 3
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BOX 5-1 A Brief Glossary of Pharmacology
Adverse drug reaction Response to a drug that is noxious Formulary List of approved or available drugs. It is often
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and unintended, and that occurs at doses normally used used by insurers to identify agents that will be reimbursed
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for prophylaxis, diagnosis, or therapy of disease or for the or paid for by the insurer.
modification of physiologic function. Generic name A formulation that contains the same
Agonist A drug that binds to a receptor and activates it, active ingredients found in the original brand formulation
producing a pharmacological response. and is bioequivalent to that formulation.
Antagonist A drug that attenuates the effects of an Half-life The period of time required for the concentration
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agonist. Antagonism can be competitive and reversible or amount of drug in the body to be reduced to exactly
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(i.e., the drug binds reversibly to a region of the receptor in one-half of a given concentration or amount.
common with the agonist) or competitive and irreversible Hypersensitivity reaction A state of altered reactivity
(i.e., the antagonist binds covalently to the agonist wherein the body reacts to a foreign substance with an
binding site, and no amount of agonist can overcome the exaggerated immune response; classified as Type I, II, III,
inhibition). or IV depending on the specific pathologic response.
Bioavailability Percentage of an administered drug that
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Immunotherapy Treatment of disease by inducing,
is available to target tissues. enhancing, or suppressing an immune response.
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Bioequivalent Pharmacologically equivalent. Loading dose A larger than normal dose administered as
Black box warning A method that the FDA uses to identify the first in a series of doses, with the other does being
unusual harm associated with an agent. Often this warning equal to each other but smaller than the first. A loading
is added to package inserts after postmarketing studies dose is administered to achieve a therapeutic amount in
identify unexpected risks linked to a drug. the body more rapidly.
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Brand name A trademarked name assigned to a drug by Nutraceutical (functional food) A food or supplement
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its manufacturer. Some brand names are similar to the (e.g., folic acid) that has specific health benefits.
generic name (e.g., pseudoephedrine/Sudafed); others Off-label use Prescription or use of a drug for conditions
suggest their indications for use (e.g., Tamiflu). other than those approved by the FDA.
Chemical name Although rarely used by prescribers and Over-the-counter (OTC) Pharmaceuticals sold without
consumers, a name of a drug that describes its chemical prescriptions.
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composition. Pharmacodynamics How drugs produce their effects, such
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Compounding Mixing or combining ingredients to as interactions at a receptor site.
produce a pharmaceutical agent. Pharmacists may perform Pharmacogenetics The study of how drugs interact with
compounding to change the form from solid pill to liquid, the genetic makeup of an individual or the genetic response
or it may be done to create a unique dose and combination to a drug; this may be one of the first clinical applications
of products for a specific individual. derived from the Human Genome Project.
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Controlled substance Pharmaceuticals as listed in Pharmacogenomics Studies that illustrate similarities
schedules found in U.S. Law 21 U.S.C. §802(32)(A). These
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agents include opiates as well as nonopiates but generally and differences in pharmacodynamic and pharmacokinetic
have a high risk of addiction, often without valid medicinal mechanisms among various individuals and people of
use. Examples include heroin. different ethnic backgrounds.
Cosmeceutical A cosmetic product that has medicinal or Pharmacokinetics The movement of drugs in the
druglike benefits. body, specifically encompassing the study of factors
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that determine the amount of chemical agents at their
Direct-to-consumer advertising Advertising of selected sites of biologic effect at various times after the agent
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drugs placed in popular media and directed to the general is administered. Pharmacokinetics is composed of four
public as opposed to providers in peer-reviewed journals. specific factors: absorption, distribution, metabolism
Dispense (furnish) The process of giving a drug to a (biotransformation), and excretion (clearance).
consumer. Pharmacotherapeutics The field concentrating on the
treatment effects of drugs. There are several subsections
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Ecopharmacology Derivation of drugs from plants, es-
pecially those found in the rainforest, as well as exploration within pharmacotherapeutics.
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of pharmacologic implications of pollutants in water that Polypharmacy The practice of treating individuals using
exert pharmaceutical-like effects, most often estrogenic multidrug regimens. This term generally is accepted to
in nature. The latter substances also have been called mean administration of five or more drugs.
ecoestrogens or xenoestrogens. (continues)
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4 PART II Primary Care
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BOX 5-1 A Brief Glossary of Pharmacology (continued)
Prescriptive authority Legal ability to prescribe Therapeutic window A point at which the plasma
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drugs, medical devices, or other regulated healthcare drug concentration is between the minimum effective
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interventions. concentration (MEC) in the plasma for obtaining the desired
Side effect A physiologic response unrelated to the drug action and the mean toxic concentration (MTC).
desired drug effects that occurs with therapeutic doses of Toxicology The branch of pharmacology that deals with
the medication. Side effects may be beneficial or negative. the nature, effects, and treatments of poisons.
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the course of the menstrual cycle, which could affect in the united States is magnesium sulfate, yet it is
the pharmacokinetics and pharmacodynamics of a not FDA approved for that indication. Methotrexate
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drug. even when women have participated in clini- (rheumatrex)—a folic acid antagonist used as a che-
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cal trials, it has been rare that an analysis of gender motherapeutic agent—has a marked predilection for
differences has been published. Moreover, clinical tri- destruction of trophoblastic tissue and is used off
als for contraceptives generally do not include many label for medical treatment of an unruptured ectopic
adolescents, as women younger than the age of 18 are pregnancy. Midwives should recognize that off-label
considered pediatric patients. Pediatrics itself is a dif- use, though it remains common, should not be under-
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ficult area in which to conduct clinical trials because taken capriciously. A legal liability potentially exists,
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of the inherent problems obtaining informed consent. especially if the drug is not yet widely accepted in
Although the FDA approves drugs for specific practice for the off-label indication.
indications, once it is marketed the same drug may be
prescribed for another use—a phenomenon is called Controlled Substances
“off-label use.” examples abound regarding off-label The u.S. Drug enforcement Administration (DeA)
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9
use. For instance, the most commonly used tocolytic was established in 1973 within the Department of
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Justice. This agency has a special role in the regu-
lation of prescription drugs that have the potential
for abuse, under the 1970 Controlled Substance Act
(CSA). The CSA has classified pharmaceuticals that
BOX 5-2 Phases of the Food and Drug can be abused into one of five schedules based on the
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Administration Drug Approval Process substance’s medicinal value, harmfulness, and po-
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tential for abuse or addiction. Schedule I is reserved
FDA Phase Description for the most dangerous drugs that have no recog-
1 Designed to determine drug dynamics nized medical use, such as LSD and heroin. Schedule
and identify drug metabolites. This phase V is the classification used for the least dangerous
drugs, such as brand-name antitussives containing
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is usually small and may be omitted if small amounts of codeine. Meperidine (Demerol) is
extensive international study has been
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conducted. a Schedule II agent. knowledge of these schedules
2 Controlled clinical trials to verify ef- is important for midwives with prescriptive author-
fectiveness and basic safety. ity because this authority is often limited to specific
3 Randomized clinical trials, usually placebo schedules. Box 5-3 lists the five schedules for con-
trolled substances.
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controlled. A registration number issued by the DeA is
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4 Postmarketing clinical trials, usually to needed to prescribe a controlled substance. In 1993,
gather information about adverse reactions, the DeA published a regulation that established a
morbidity, and mortality that can be ob- new category under which healthcare providers other
tained only in larger groups.
than physicians, dentists, veterinarians, or podiatrists
could receive individual DeA registration numbers
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