Chapter 3 Flashcards
Life Span Considerations
- Pregnancy
- Breast-feeding
- Neonatal and Pediatric
- Elderly
First trimester is the period of….
Greatest danger for drug-induced development defects
Drugs cross the placenta by…
diffusion
During the last trimester….
the greatest percentage of maternally absorbed drug gets to the fetus
FDA Pregnancy Categories
A, B, C, D, X
Category A
Studies indicate no risk to human fetus
Category B
Studies indicate no risk to animal fetus, information for humans is not available
Category C
Adverse effects reported in animal fetus, information for humans not available
Category D
Possible fetal risk in humans reported, however, considerations of potential benefits vs. risk may in selected cases warrant use of these drugs in pregnant women
Category X
Fetal abnormalties reported and positive evidence of fetal risk in humans available from animal and or human studies. These drugs should not be used in pregnant women
Breast Feeding
Breast fed infants are at risk for exposure to drugs consumed by the mother
*Consider risk-to-benefit ration
Neonatal and Pediatric Considerations:
Absorption
- Gastric pH less than acidic
- Gastric emptying is slowed
- Intramuscular absorption faster and irregular
Neonatal and Pediatric Considerations:
Distribution
- The younger the person, the greater the % of total body water
- Greater TBW means fat content is lower
- Decreased level of protein binding
- Immature blood-brain-barrier- more drugs enter the brain
Neonatal and Pediatric Considerations:
Metabolism
- Liver immature, does not produce enough microsomal enzymes
* Older children may have increased metabolism, requiring higher doses than infants
Neonatal and Pediatric Considerations:
Excretion
- Kidney immaturity affects glomerular filtration rate and tubular secretion
- Decreased perfusion rate of the kidneys may reduce excretion of drugs
Factors Affecting Pediatric Drug Dosages
- 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
Methods of Dosage Calculation for Pediatric Patients
- Body surface area method
- using the West monogram
- Body weight dosage calculations
- using mg/kg
The Elderly:
- Older than age 65
- Use of OTC medications
- Increased incidence of chronic illnesses
- Polypharmacy
Physiologic Changes in the Elderly Patient
- Cardiovascular
- Gastrointestinal
- Hepatic
- Renal
The Elderly:
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:
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:
Metabolism
- Aging liver produces fewer microsomal enzymes, affecting drug metabolism
- Reduced blood flow to the liver
The Elderly:
Excretion
- Decreased glomerular filtration rate
* Decreased number of intact nephrons
