1. Drug Action Across the Life Span
Chapter 3
Drug Action
Across the Life Span
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2. Chapter 3
Lesson 3.1
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3. Objectives Discuss the effects of patient age on drug action
Discuss the role of genetics and its influence on drug action
Cite major factors associated with drug absorption, distribution, metabolism, and excretion in the pediatric and geriatric populations
Cite major factors associated with drug absorption, distribution, metabolism, and excretion in men and women
Gender-specific medicine is a developing science that looks at how men and women perceive and experience disease, as well as how pharmacokinetics affect each gender.
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4. Therapeutic Drug Monitoring
Entails measurement of a drug’s concentration in biologic fluids to correlate the dosage administered and the level of medicine in the body with the pharmacologic response
Timing of drug’s administration and collection of specimen are crucial to accurate interpretation
Essential in neonates, infants, and children, given the major physiologic changes that affect drug ADME.
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5. Use of Monitoring Parameters
Before administering medicine
Assess expected therapeutic actions, side effects, reportable adverse effects, and probable drug interactions
Monitor parameters related to patient’s age
Absorption, distribution, metabolism, and excretion of drugs are different for infants and children
These parameters often change; therapeutic drug monitoring is very important for pediatric patients.
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6. Use of Monitoring Parameters: Pediatric Patients
Infants and young children are more susceptible to dehydration
Weight variation affects dosage
Aspirin is never administered to children
Allergic reactions occur rapidly in children, most commonly to antibiotics
Why should aspirin not be given to children? (Reye’s syndrome)
What two common drugs are appropriate analgesics and antipyretics for children? (Ibuprofen and acetaminophen)
What is it called when a medication is prescribed for a child but there is no FDA-approved use for children? (Off-label use)
What symptoms may be indicative of an allergic reaction? (Urticaria, difficulty breathing, swelling in the oropharynx)
If the patient is exhibiting signs of a severe allergic reaction, what is the appropriate nursing intervention?
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7. Use of Monitoring Parameters: Geriatric Patients
Drug therapy
Take thorough drug history and nutritional assessment
Determine whether new symptoms have been induced by existing medicines
Gradually taper dosage when discontinuing drug
Start at 1/3 to 1/2 normal dosage when initiating therapy; gradually increase
Review regimen periodically
Use calendars or pill boxes to avoid confusion with multidrug regimens.
Offer assistance in destroying old medicines.
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8. Changing Drug Action With Gender Considerations
In nearly every body system, men and women function differently
Men and women perceive and experience disease differently
Pharmacogenetics
Fundamental questions remain about how humans function and the effect of disease on function
Polymorphisms
Naturally occurring variations in the structures of genes
Having parameters or guidelines for both men and women is one of the goals of this research.
Women’s studies need to include the different phases of the menstrual cycle, as well as pre- and post-menopausal women.
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9. Drug Absorption: Age Considerations
Special considerations for pediatric and older adult patients
Differences in muscle mass, blood flow, and inactivity affect medicines given intramuscularly
Topical and transdermal administration differs in the very young and the very old
Factors that place older patients at risk
Reduced renal and hepatic function
Polypharmacy – multiple-drug therapy required by chronic illness
A greater likelihood of malnourishment
Discuss why the amount of muscle mass and blood flow affect the absorption of IM drugs.
Describe why IM drugs may be absorbed differently in older adults compared with younger adults.
Explain why topical and transdermal medications may be absorbed differently in children and older adults.
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10. Drug Absorption: Age Considerations (cont’d)
Gastrointestinal absorption influenced by:
Gastric pH
Gastric emptying time
Enzymatic activity
Blood flow of mucous lining and intestines
Discuss why intestinal blood flow influences drug absorption.
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11. Drug Absorption: Age Considerations for Infants
Topical administration in infants is effective because:
Outer layer of skin (stratum corneum) not fully developed
Skin more fully hydrated; plastic diaper increases skin hydration
Inflammation (diaper rash) increases absorption
Drugs are fat soluble or water soluble. Drugs that are water soluble will be absorbed more readily through an aqueous medium.
Discuss how diaper rash increases absorption of topical medications as well as why a plastic diaper increases the water content of the skin.
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12. Drug Absorption: Age Considerations for Geriatric Patients
Difficult to predict in geriatric patients
Dermal thickness decreases with age and may enhance absorption
Drying, wrinkling, and decreased hair follicles decrease absorption
Decreased cardiac output and diminishing tissue perfusion also affect absorption
Why does wrinkling of the skin and a decrease in the number of hair follicles affect the absorption of topical medications? (Because they alter the surface area available for drug absorption)
Why does diminished tissue perfusion decrease absorption of topical medications? (Because blood flow enhances absorption of drugs)
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13. 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
The adverse effects of these drugs are more common.
Use these medications with older adults only as a last resort (e.g., when treatment with other medications has failed).
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14. Drug Absorption: Gender Considerations
Increased potential for toxicity and slower absorption times in women
Empty solids more slowly
Have greater gastric acidity
Have lower gastric levels of alcohol dehydrogenase needed to metabolize alcohols
The exact contribution of gender to drug absorption has not been completely outlined.
Discuss the effect of a low level of alcohol dehydrogenase in women.
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15. Drug Distribution
Depends on pH, body water concentrations, presence and quantity of fat tissue, protein binding, cardiac output, and regional blood flow
Infants have larger volume of water content and require higher dose
With age, total body water decreases and fat increases
Highly fat-soluble drugs take longer to act and accumulate in fat tissues, increasing potential for toxicity
Infants have higher body water concentrations. What effect does this have on drug distribution? (Increases drug distribution)
Women have a higher percentage of body fat than men. What effect does this have on drug distribution? (May decrease drug distribution)
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16. Drug Distribution (cont’d)
Protein binding
Drugs that are relatively insoluble are transported in circulation by binding to plasma proteins
Age considerations
Some drugs have lower protein binding in neonates and require larger loading dose
Albumin levels decrease with age
Gender considerations
Some differences between men and women in globulin proteins
Drugs that are highly fat soluble include antidepressants, phenothiazines, benzodiazepines, and calcium channel blockers.
Lower protein binding may lead to greater immediate pharmacologic effect.
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17. Drug Metabolism Drug metabolism
Process by which the body inactivates medicine
Affected by genes, diet, age
Liver weight and hepatic blood flow decrease with age
Explain why a decrease in liver weight and hepatic blood flow affect drug metabolism. (Because it may cause a decline in the liver’s ability to metabolize a drug)
Discuss the effect liver disease has on drug metabolism and why. (It will affect the patient’s ability to metabolize a drug, increasing the risk for drug toxicity)
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18. Drug Excretion
Metabolites of drugs (and sometimes the drug itself) eventually excreted
Preterm infant has 15% of adult renal capacity; fully functional by 9 to 12 months
Decreased renal function with age
No prediction of renal function can be based solely on age because of wide individual variation in changes
Occasionally drug metabolites can be pharmacologically active.
Why is it important to know that the renal capacity of an infant is less than that of an adult? (Because it will affect excretion of drugs)
What are the two common blood tests that measure renal function? (Blood urea nitrogen [BUN] and creatinine [Cr])
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19. 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
Alcohol and tobacco are not essential nutrients, and have been proven to have detrimental effects on the fetus.
Herbal medications are not regulated by the FDA and pose a risk to the pregnant patient, including miscarriage.
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20. Drugs Known to be Teratogenic
Drug classifications known to be teratogenic
Androgenic and estrogenic hormones
ACE inhibitors, ethanol, tetracycline
Thalidomide, vitamin A, warfarin
Angiotension II receptor antagonists
Anticonvulsants, antimanic agent, antithyroid
Chemotherapy, statins, cocaine
Discuss teratogenic drugs or any substances that cause birth defects.
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21. Use of Monitoring Parameters: Breast-Feeding Infants
Some drugs are known to enter breast milk and harm the nursing infant
Discuss all medications with physician
Take medicine immediately after breast-feeding or just before infant’s longest sleeping period
For many drugs that are excreted in breast milk, no one knows with certainty what effect they will have on the infant.
Medications include prescription, nonprescription, and herbal products.
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