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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.
4Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
Drug Therapy During Breastfeeding
Breastfed infants are at risk for exposure to drugs consumed by the mother
Consider risk-to-benefit ratio
5Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
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)
Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 8
Metabolism Liver immature, does not produce enough microsomal enzymes Older children may have increased metabolism, requiring higher
doses than infants Other factors
Neonatal and Pediatric Considerations: Pharmacokinetics (cont’d)
Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 9
Excretion Kidney immaturity affects glomerular filtration rate and tubular
secretion Decreased perfusion rate of the kidneys may reduce excretion of
drugs
Neonatal and Pediatric Considerations: Pharmacokinetics (cont’d)
Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 10
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
Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 11
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
Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 12
Classroom Response Question
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.
14Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
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
Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 15
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
Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 17
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)
Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 18
Metabolism Aging liver produces fewer microsomal enzymes, affecting drug
metabolism Reduced blood flow to the liver
The Elderly: Pharmacokinetics (cont’d)
Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 19
Excretion Decreased glomerular filtration rate Decreased number of intact nephrons
The Elderly: Pharmacokinetics (cont’d)
Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 20
Analgesics, including NSAIDs and opioids Anticoagulants Anticholinergics Antidepressants Antihypertensives Cardiac glycosides (digoxin) Sedatives and hypnotics, CNS depressants Thiazide diuretics
The Elderly:Problematic Medications
Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 21
Classroom Response Question
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
22Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
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