Pharmacology

Pharmacology GENERAL CONCEPTS OF PHARMACOLOGY 1. Absorption: The movement of the drug from the site of administration into the blood. ✽ No medication has a single action; all medications a. Drug absorption can be altered by the have the potential to alter more that one body function. increase or decrease in gastric emptying, by For example, aspirin may be given for anti-inflammatory changing the gastric pH, or by forming drug action for arthritis, or for antiplatelet action to prevent complexes. strokes. b. Administration affects absorption, for example subcutaneous injection vs oral ✔ NURSING PRIORITY: Many medications have administration. several actions that are desirable. Carefully evaluate 2. Distribution: The movement of the drug through the question to determine the desired response of the the body. Drug metabolism and excretion as well as medication for the specific client situation. cardiac output will affect the distribution of a drug. 3. Metabolism: the alteration of the drug structure, the alterations occur in the liver with excretion by the A. Desired action: the desired, predictable response for kidney. which the medication is administered. 4. Excretion: Changes in liver and renal function as B. Side effects (drug reaction): the undesirable or unwant- well as changes in cardiac output will affect the ed response; frequently predictable. excretion of a drug. C. Unpredictable response: the unusual response to a medi cation. ✔ OLDER ADULT PRIORITY: Creatinine clearance 1. Idiosyncratic reaction: an individual, unexpected re is a more effective indication of renal function that serum sponse to a medication. creatinine in older adults. 2. Allergic reaction: may or may not occur with the initial dose of medication; occurs with subsequent F. Potential for Abuse: Controlled Substances Act, doses because it requires that the immune system 1970, defines rules for the manufacture and respond with the production of antibodies in order distribution of drugs that are considered to have a to trigger the allergic reaction. potential for abuse. D. The Drug Amendments of 1962 made it mandatory that 1. 5 Categories of medications: Schedules I, II, III, each medication have one official name. IV, V—potential for abuse decreases with each 1. Generic name (nonproprietary): the official category, medications in Schedule V have lowest designated name that the medication is listed under potential for abuse. in official publications. 2. Schedule I drugs are highly addictive 2. Chemical name: designates the specific chemical (e.g., heroin) and are not used in therapeutic composition of the medication. administration of medications, Schedule V 3. Trade name (proprietary name, brand name): the drugs (e.g., diphenoxylate hydrochloride name designated and registered by a specific [Lomotil]) have the lowest potential for abuse. manufacturer. Drug Actions TEST ALERT: Typically, the medications on the NCLEX-PN examination will be identified with A. Desired action: the desired, predictable response for both the generic and trade name—for example: which the medication is administered. diazepam (Valium). B. Adverse drug reactions (ADR): an undesirable drug effect, ranging from mild untoward effects to severe responses. E. Pharmacokinetic process: Consists of four phases - absorption, distribution, metabolism, or excretion, acting together to determine the concentration of a drug at its site of action. 69 70 CHAPTER 4 Pharmacology E. Drug incompatibility: a chemical or physical reaction ✔ OLDER ADULT PRIORITY: ADRs are 7 times that occurs when two or more drugs are combined in more common in older adults than in young adults. vitro (outside the body). F. Breast-feeding: advise women who are lactating to 1. Side effects: undesirable drug effects, ranging from always advise their health care provider; medications mild untoward effects to severe responses that occur may be excreted in breast milk. at normal drug dosages. 2. Toxicity: drug reactions that primarily occur as a TEST ALERT: Use critical thinking skills when result of receiving an excessive dose (e.g., medica- considering the effects and/or outcomes of medication error, poisoning); can also include severe reactions; identify any contraindications to administration tions (anaphylaxis) that occur regardless of the dose. of a prescribed or OTC medication. 3. Allergic reactions: drug reaction that occurs as a result of prior sensitization and results in an immune G. Food and Drug Administration pregnancy risk categories response. Intensity can range from very mild to very (Table 4-1). severe (anaphylaxis). 4. Idiosyncratic effect: an uncommon drug response. Herbal Supplements C. Tolerance: an increased dose is required to maintain ex- A. Use of herbs to treat health problems is the most pected drug response. For example, when a client with common form of alternative medicine, which can be chronic pain may requires higher doses of an analgesic defined as treatment practices that are not widely to achieve pain relief. accepted or practiced by mainstream clinicians in a D. Dependence: an expected response to repeated use of a given culture. drug, resulting in physical signs and symptoms of with- B. The word natural is not synonymous with safe! drawal when the serum drug level decreases suddenly. Remember, poison ivy and tobacco are natural, too. For example, when a client abruptly stops taking a strong C. Some commonly used medicinal herbs (Table 4-2). opioid agonist (methadone) and develops symptoms of withdrawal. E. Addiction: the continued use of a psychoactive sub- ✔ NURSING PRIORITY: Unlike conventional stance regardless of physical, psychologic, or social drugs, herbal and other dietary supplements can be mar- harm. keted without any proof of safety or efficacy. Dietary supplements are not regulated by the FDA. Drug Interactions A. An altered or modified action or effect of a drug as a result of interaction with one or more drugs. It is not an MEDICATION ADMINISTRATION adverse drug reaction or drug toxicity. B. Drug incompatibility: a chemical or physical reaction that occurs between two or more drugs outside the body. ✔ NURSING PRIORITY: The nurse’s responsibil- ity in administering medication is influenced by three primary factors: nursing guidelines for safe medication TEST ALERT: Assess client for actual or potential administration, pharmacological implications of the side effects and adverse effects of medications; medication, and the legal aspects of medication adminis- identify symptoms/evidence of allergic reactions to tration. medications; implement procedures to counteract adverse effects of medications; evaluate and document Nursing Responsibilities in Medication client response to actions taken to counteract side effects and adverse effects of medications. Administration A. Follow the “7 Rights” of medication administration. C. Potentiation effect (synergistic effect): if two or more 1. Right medication. drugs are given together and this increases the 2. Right dosage. therapeutic effects, it is beneficial; if it increases adverse 3. Right route of administration. effects, it may be detrimental. For example, a diuretic 4. Right time. and a beta blocker may be give together for hypertension. 5. Right client. D. Antagonistic or inhibitory effect: if two or more drugs 6. Right charting (documentation). are given together, one may inhibit the effect of the 7. Right technique other; this may be beneficial or detrimental. For example, naloxone (Narcan) may be given to suppress the effects of morphine. TEST ALERT: Administer medications according to the “7 Rights” of medication administration. CHAPTER 4 Phamacology 71 Table 4-1 FOOD AND DRUG ADMINISTRATION PREGNANCY RISK CATEGORIES Category Description A Remote Risk of Fetal Harm: Adequate and well-controlled studies in pregnant women have not shown an increased risk of fetal abnormalities. B Slightly More Risk Than A: Animal studies have revealed no evidence of harm to the fetus; however, there are no adequate and well-controlled studies in pregnant women. or Animal studies have shown an adverse effect, but adequate and well-controlled studies in pregnant women have failed to demonstrate a risk to the fetus. C Greater Risk Than B: Animal studies have shown an adverse effect, and there are no adequate and well- controlled studies in pregnant women. No animal studies have been conducted, and there are no adequate and well-controlled studies in pregnant women. D Proven Risk of Fetal Harm: Studies—adequate well-controlled or observational—in pregnant women have demonstrated a risk to the fetus. However, the benefits of therapy may outweigh the potential risk. X Proven Risk of Fetal Harm: Studies—adequate well-controlled or observational—in animals or pregnant women have demonstrated positive evidence of fetal abnormalities. The use of the product is contrain dicated in women who are or may become pregnant. Modified from Lehne RA: Pharmacology for nursing care, ed 6, St. Louis, 2007, Saunders; and Meadows M: Pregnancy and drug dilemma, FDA Consumer Magazine, May-June 2001. Available at www.fda.gov/fdac/features/2001/301_preg.html. Table 4-2 COMMONLY USED MEDICINAL HERBS Medicinal Herb Drug Interactions • Black cohosh is a popular treatment for acute symptoms of meno- May potentiate hypotensive effects of antihypertensive drugs, pause and premenstrual syndrome (PMS). Minor side effect of as well as hypoglycemic action of insulin and oral upset stomach may occur. hypoglycemics. • Feverfew for treatment of migraine, fever; stimulates

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