Chapter 3 Flashcards
During which trimester are the greatest percentage of maternally absorbed drugs get to the fetus?
The last trimester
Which three factors contribute to the safety or potential harm of drug therapy during pregnancy?
- drug properties
- fetal gestational age
- maternal factors
What are drug characteristics that increase the likelihood of drug transfer via breastfeeding?
- fat solubility
- low molecular weight
- high concentration
Are maternal drug levels higher in breastmilk or maternal circulation?
maternal circulation
neonate
birth to 1 month
infant
1 month to 12 months
child
1 and 12 years of age
LIfespan considerations for the pediatric patient
- absorption
- distribution
- metabolism
- excretion
Category A
Studies indicate no risk to the human fetus
Category B
Studies indicate no risk to the animal fetus; information for humans is not availible
Category C
Adverse effects reported in the animal fetus; information for humans is not availible
Category D
Possible fetal risk in humans has been reported; however, in selected cases consideration of the potential benefit versus risk may warrant use of these drugs in pregnant women
Category X
Fetal abnormalities have been reported, and positive evidence of fetal risk in humans is available from animal and/or human studies. These drugs are not be used in pregnant women.
Neonatal and pediatric considerations for absorption
- gastric pH less acidic
- gastric emptying slowed
- intramuscular absorption faster and irregular
Neonatal and pediatric considerations for 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 for metabolism
- liver immature, does not produce enough microsomal enzymes
- older children may have increased metabolism, requiring higher doses than infants
Neonatal and pediatric considerations for excretion
- kidney immaturity affects glomerular filtration rate and tubular secretion
- decreased perfusion rate of the kidney may reduce excretion of drugs
When are teratogens most deadly to fetuses?
First trimester
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
- 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
- body surface are method
- always use weight in kilograms, not pounds
- always use centimeters, not inches
- body weight dosage calculations
- -uses mg/kg
Considerations for older adult patients
- high use of medications
- polypharmacy
- noncompliance, nonadhherence
- increased incidence of chronic illnesses
- sensory and motor deficits
Older adult considerations for pharmokinetics
- more sensitive to drugs than younger adults and with greater variation in pharamacokinetics
- multiple and severe illnesses
- multipple-drug therapy
- poor adherance
Cardiovascular changes in older adults
- decreased cardiac output = decreased absorption and distribution
- decreased blood flow = decreased absorption and distribution
Gastrointestinal changes in older adults
- increase pH = altered absorption
- decreased peristalasis = delayed gastric emptying
Heptic changes in older adults
- decrease in enzyme production = decreased metabolism
- decreased blood flow = excretion
renal changes in older adults
- decreased blood flow = decreased excretion
- decreased function = decreased excretion
- decreased glomerular filtration rate = decreased excretion
elderly distribution pharmacokinetics
- lower total water percentages
- increased fat content
- decreased production of proteins by the liver, resulting in decreased protein binding of drugs
elderly metabolism pharmacokinetics
-aging liver produces fewer microsomal enzymes, affecting drug metabolism
elderly reduced blood flow to the liver/excretion pharmacokinetics
- decreased glomerular filtration rate
- decreased number of intact nephrons
Rules for the elderly!
-start with low dosages and go slow with increasing dosages
