Chapter 3 Lifespan Considerations Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Chapter 3

Lifespan Considerations

Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Drug Therapy During Pregnancy

Drugs cross the placenta by diffusion Factors affecting safety:

Drug properties Fetal gestational age Maternal factors

FDA has implemented pregnancy safety categories

2Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Classroom Response Question

When teaching a pregnant woman about the use of drugs during pregnancy, which statement will the nurse include?

A.Exposure of the fetus to drugs is most detrimental during the second trimester of pregnancy.

B.Pregnant women must never take drugs to control high blood pressure.

C.Drug transfer to the fetus is most likely to occur during the last trimester of pregnancy.

D.The fetus is at greatest risk for drug-induced developmental defects during the second trimester of pregnancy.


Drug Therapy During Breastfeeding

Breastfed infants are at risk for exposure to drugs consumed by the mother

Consider risk-to-benefit ratio


Absorption Gastric pH less acidic Gastric emptying slowed Intramuscular absorption faster and irregular

Neonatal and Pediatric Considerations: Pharmacokinetics

Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 7

Distribution Greater total body water means lower fat content Decreased level of protein binding Immature blood-brain barrier—more drugs enter the brain

Neonatal and Pediatric Considerations: Pharmacokinetics (cont’d)


Metabolism Liver immature, does not produce enough microsomal enzymes Older children may have increased metabolism, requiring higher

doses than infants Other factors



Excretion Kidney immaturity affects glomerular filtration rate and tubular

secretion Decreased perfusion rate of the kidneys may reduce excretion of

drugs



Skin is thin and permeable Stomach lacks acid to kill bacteria Lungs have weaker mucus barriers Body temperatures less well regulated, and dehydration

occurs easily Liver and kidneys are immature, impairing drug

metabolism and excretion

Factors Affecting Pediatric Drug Dosages


Body surface area method Uses the West nomogram

Always use weight in kilograms, not pounds Body weight dosage calculations

Uses mg/kg

Methods of Dosage Calculation for Pediatric Patients



When administering medications to pediatric patients, the nurse understands that the dosage calculations for pediatric patients are different than for adults because pediatric patients

A. are more likely to develop edema.

B. have more stomach acid.

C. have skin that is less permeable.

D. have immature liver and kidney function, resulting in impaired drug metabolism and excretion.


Elderly: older than age 65 High use of medications Polypharmacy Noncompliance, nonadherence Increased incidence of chronic illnesses Sensory and motor deficits

Considerations for Elderly Patients


Absorption Gastric pH less acidic Gastric emptying slowed Movement through GI tract slowed Blood flow to GI tract reduced Use of laxatives may accelerate GI motility

The Elderly: Pharmacokinetics


Distribution Lower total body water percentages Increased fat content Decreased production of proteins by the liver, resulting in

decreased protein binding of drugs (and increased circulation of free drugs)

The Elderly: Pharmacokinetics (cont’d)


Metabolism Aging liver produces fewer microsomal enzymes, affecting drug

metabolism Reduced blood flow to the liver



Excretion Decreased glomerular filtration rate Decreased number of intact nephrons



Analgesics, including NSAIDs and opioids Anticoagulants Anticholinergics Antidepressants Antihypertensives Cardiac glycosides (digoxin) Sedatives and hypnotics, CNS depressants Thiazide diuretics

The Elderly:Problematic Medications



Which does the nurse identify as a pharmacokinetic change that occurs in the elderly?

A.Gastric pH is more acidic

B.Fat content is decreased because of increased lean body mass

C.Increased production of proteins by the liver

D.The number of intact nephrons is decreased


Chapter 3 Lifespan Considerations Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

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