Drug Action Across the Life Span - Pharmacology for Nurses

Chapter 3 Drug Action Across the Life Span Clayton’s Basic Pharmacology for Nurses, 19th edition Michelle Willihnganz, MS, RN, CNE 1  Lesson 3.1 Drug Action Across the Life Span...

Chapter 3 Drug Action Across the Life Span Clayton’s Basic Pharmacology for Nurses, 19th edition Michelle Willihnganz, MS, RN, CNE 1  Lesson 3.1 Drug Action Across the Life Span (1 of 2) 1. Explain the impact of the placebo effect and the nocebo effect. 2. Identify the importance of drug dependence and drug accumulation. 3. Discuss the effects of age on drug absorption, distribution, metabolism, and excretion. 4. Explain the gender-specific considerations of drug absorption, distribution, metabolism, and excretion. 2  Lesson 3.1 Drug Action Across the Life Span (2 of 2) 5. Describe where a nurse will find new information about the use of drugs during pregnancy and lactation. 6. Discuss the impact of pregnancy and breastfeeding on drug absorption, distribution, metabolism, and excretion. 7. Discuss the role of genetics and its influence on drug action. 3  How Age and Body Weight Affect Drug Therapy  Age  Infants and the very old tend to be most sensitive to drug effects  Aging process brings about changes in body composition and organ function  Body weight  Considerably overweight patients may require an increase in drug dosage to attain the same therapeutic response 4  How Gender and Metabolic Rate Affect Drug Therapy  Gender  In almost every body system, men and women function differently; experience disease differently  Metabolic rate  Patients with higher-than-average metabolic rate tend to metabolize drugs more rapidly  Chronic smoking enhances metabolism of some drugs 5  How Illness and Psychology Affect Drug Therapy  Illness  Pathologic conditions may alter rate of absorption, distribution, metabolism, and excretion of drug  Patients with kidney failure generally will excrete drugs at a slower rate  Psychology  Attitudes and expectations play a major role in a patient’s response to therapy; willingness to take medication as prescribed 6  Placebo and Nocebo  Placebo effect: Patient’s positive expectation can positively affect the outcome  Nocebo effect: Patient’s negative expectations can result in a less-than-optimal outcome 7  Drug Tolerance  Occurs when a person begins to require a higher dosage of a medication to produce the same effects that a lower dosage once provided  Can be caused by psychological dependence 8  Drug Dependence  Person is unable to control his/her ingestion of drugs  Physiologic: Person develops withdrawal symptoms if drug is withdrawn  Psychological: Person is emotionally attached to a drug 9  Cumulative Effect  Drug accumulation occurs when the next dose is given before the previously given drug has been metabolized or excreted  May result in drug toxicity  Carcinogenicity: Ability of a drug to induce living cells to mutate and become cancerous 10  Factors That Influence Absorption (1 of 4)  Absorption: Process by which drugs are absorbed in the body; most common is via GI tract; other routes are parenteral and topical  Age  Premature infants: Slower gastric emptying time may allow increased absorption 11  Factors That Influence Absorption (2 of 4)  Age  Neonates: IM absorption erratic, reduced gastric acidity  Infants: Topical absorption increased 12 Factors That Influence Absorption (3 of 4)  Geriatric patients IM absorption erratic Reduced salivary flow makes swallowing difficult Transdermal absorption hard to predict Timed-release/enteric-coated tablets cannot be crushed Reduced GI acidity affects absorption Slower gastric emptying time Decreased GI motility and blood flow 13  Factors That Influence Absorption (4 of 4)  Gender  A woman’s stomach empties solids more slowly than a man’s does  Slower gastric emptying time may allow drug to stay in contact with absorptive tissue longer  Body weight may aggravate the higher blood alcohol level and state of intoxication in women and men 14  Factors That Influence Distribution (1 of 2)  Distribution: Ways in which drugs are transported to site of action  Depends on pH, body water concentrations, fat tissues, protein binding, cardiac output, and blood flow  Infants  Higher total body water content, requiring higher dose on mg/kg basis  Lower body fat  Reduced protein binding in neonates 15  Factors That Influence Distribution (2 of 2)  Geriatric patients: Total body water content decreases  Gender: Total body fat higher in females 16  Factors That Influence Metabolism  Metabolism: Process whereby the body inactivates medications; primarily occurs in the liver  Infants: Enzymes take several weeks to a year to develop  Older adults: Liver cells decrease, blood flow decreases  All ages: Genetics, smoking, diet, other medications, liver disorders 17  Factors That Influence Excretion (1 of 2)  Drug metabolites and the drug itself are excreted from the body  Preterm infants have 15% of the renal capacity of an adult  Neonates have 35%  Full adult function occurs at 9 to 12 months 18  Factors That Influence Excretion (2 of 2)  Geriatric  Decreased renal blood flow  Reduced cardiac output  Loss of glomeruli  Decreased tubular function  Serum creatinine levels give estimate of renal function 19  Therapeutic Drug Monitoring  Measurements of drug concentration in blood sample  Very essential in neonates, infants, children  Dosage and frequency of medications can be adjusted to maintain therapeutic level of potentially toxic drugs 20  Monitoring Parameters  All medicines have a number of parameters, expected therapeutic actions, common adverse effects, serious adverse effects, and any drug interactions  Crucial that normal values for monitoring parameters and laboratory tests be related to the age of the patient being monitored 21  Pediatric Patients  Dosage adjustments expected during growth  Measure liquid medications using mL  Use appropriate dilution  Verify dosage prior to giving  Aspirin use linked with Reye’s syndrome  Allergic reactions occur rapidly in children 22  Geriatric Patients (1 of 2)  Complete a thorough drug history, including prescription, OTC, herbal medications, and nutritional status  Evaluate vision and motor skills  When evaluating a new symptom, determine whether it was induced by a medication already prescribed  Start with smaller doses and gradually increase 23  Geriatric Patients (2 of 2)  Keep multidrug regimen simple  Review if any medications can be discontinued  Assess ability to pay for medications  Polypharmacy: Multidrug therapy 24 Potentially Inappropriate Medications for Geriatric Patients  Includes medications that should be avoided and those that are rarely appropriate: Some barbiturates, benzodiazepines, and some narcotics  Some are considered appropriate to give only with certain indications but may have potentially adverse reactions 25  Audience Response Question 1  Which patient has the greatest percentage of body water? a) Older adult b) Middle-aged person c) Infant d) Toddler 26  Audience Response Question 2  Which type of topical drug is more readily absorbed by infants? a) Fat-soluble b) Water-soluble c) Emollient d) Protective 27  Audience Response Question 3  Which form of medication is more easily administered for a toddler who requires a course of antibiotics? a) Enteric b) Capsules c) Tablets d) Liquid 28  Audience Response Question 4  It is important to maintain therapeutic levels of drugs to avoid the complications of being over- or undermedicated. If a drug level of 0.5 to 2 ng/mL is considered therapeutic, a drug level of 0.45 ng/mL is considered to be what? a) Toxic b) Therapeutic c) Subtherapeutic d) Tolerant 29  Audience Response Question 5  Due to the decreased protein-binding capacity in preterm infants, what adjustment in dosage of protein-binding drugs would need to made? a) The dosage should be decreased. b) The dosage should be increased. c) The dosage should be kept at the same level. d) Protein-binding drugs are not administered to infants. 30  Pregnant Patients  Fetus is exposed to substances in mother’s blood  Teratogens: Drugs that cause abnormal development of fetal tissues 31  Use of Monitoring Parameters: Pregnant Women  Avoid drugs if at all possible  When taking woman’s history, be alert to possibility of pregnancy  Instruct patient to avoid drugs, alcohol, and tobacco  Try nonpharmacologic treatments before using medicines  Avoid herbal medicines 32  Drugs Known to be Teratogenic  Androgenic and estrogenic hormones  ACE inhibitors, ethanol, tetracycline  Thalidomide, vitamin A, warfarin  Angiotensin II receptor antagonists  Anticonvulsants, antimanic agents, antithyroid  Chemotherapy, statins, cocaine 33  Use of Monitoring Parameters: Breastfeeding Infants  Some drugs are known to enter breast milk and harm the nursing infant  Discuss all medications with health care provider  Take medicine immediately after breastfeeding or just before infant’s longest sleeping period 34  Genetics and Drug Metabolism (1 of 2)  Genetics: Study of how living organisms inherit the traits of their ancestors, including function of metabolic pathways  Genome: Complete package of genetic coding of an organism  Pharmacogenetics: Study of how drug response may vary according to inherited differences 35  Genetics and Drug Metabolism (2 of 2)  Significant differences can occur among racial and ethnic groups  Most studies to date have concentrated on cardiovascular and psychiatric drugs, analgesics, antihistamines, and ethanol  Monoclonal antibodies are early examples of medicines that were synthesized to attack certain types of cancers 36 Questions? 37