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Chapter 3
Drug Action
Across the Life Span
Mosby items and derived items © 2010, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Chapter 3
Lesson 3.1
Mosby items and derived items © 2010, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 2
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
Mosby items and derived items © 2010, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 3
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
Mosby items and derived items © 2010, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 4
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
Mosby items and derived items © 2010, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 5
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
Mosby items and derived items © 2010, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 6
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
Mosby items and derived items © 2010, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 7
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
Mosby items and derived items © 2010, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 8
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
Mosby items and derived items © 2010, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 9
Drug Absorption:
Age Considerations (cont’d)
• Gastrointestinal absorption influenced by:

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Gastric pH
Gastric emptying time
Enzymatic activity
Blood flow of mucous lining and intestines
Mosby items and derived items © 2010, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 10
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
Mosby items and derived items © 2010, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 11
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
Mosby items and derived items © 2010, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 12
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
Mosby items and derived items © 2010, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 13
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
Mosby items and derived items © 2010, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 14
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
Mosby items and derived items © 2010, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 15
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
Mosby items and derived items © 2010, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 16
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
Mosby items and derived items © 2010, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 17
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
Mosby items and derived items © 2010, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 18
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
Mosby items and derived items © 2010, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 19
Drugs Known to be
Teratogenic
• Drug classifications known to be teratogenic
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Androgenic and estrogenic hormones
ACE inhibitors, ethanol, tetracycline
Thalidomide, vitamin A, warfarin
Angiotension II receptor antagonists
Anticonvulsants, antimanic agent, antithyroid
Chemotherapy, statins, cocaine
Mosby items and derived items © 2010, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 20
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 breastfeeding or just before infant’s longest
sleeping period
Mosby items and derived items © 2010, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 21