Exam 4 - OB/GYN Flashcards
(172 cards)
PREGNANCY AND LACTATION
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Thalidomide
Thalidomide
- Used as anxiolytic for pregnant patients.
- Teratogen.
- Causes birth defects of limbs.
Kefauver-Harris Drug amendment to food, drug, and cosmetic act
-Need to prove efficacy and safety now
1st trimester
- Most risk for teratogenic effects on fetus
- Vision organogenesis
What drugs used most commonly during pregnancy?
90% of women take at least one medication during pregnancy
OTC medications
- Acetaminophen – 65% of pregnant women used; benign
- Ibuprofen – 18%
- Pseudoephedrine – 15%
Antidepressants
Teratogenesis
Any significant postnatal change in function or form in an offspring after prenatal treatment.
Congenital Anomalies
Includes congenital malformations and those defects related to change in function.
Congenital Malformations
Structural abnormalities of prenatal origin that are present at birth and seriously interfere with viability or physical well being of fetus.
Examples of Known Teratogens (non-inclusive)
ACE Inhibitors Androgenic hormones Cigarette smoking Cocaine Warfarin (Coumadin®) Isotretinoin (Accutane®) Lithium Phenytoin Thalidomide Valproic acid
Isotretinoin (Accutane®)
REMS
Determinants of Teratogenicity
Epidemiological Studies
- Case reports, Case control, Cohort studies
- Voluntary reporting systems
- No randomized controlled trials
Animal studies
-Beneficial in determining the relative toxicity of an agent usually; can NOT be extrapolated directly to humans.
Pharmaceutical Industry Disclaimer:
-The safe use of this drug in pregnancy has not been established and it should only be used if the anticipated BENEFITS outweigh the potential risks…
Stages of Fetal Development
Pre-implantation and presomite stages:
0-14 days post-conception
Organogenesis
~14-56 days post-conception
Most critical period; organs start to develop (1st trimester)
Fetal period
~57 days to 40 weeks
Histogenesis and functional maturation
How do drugs effect developing fetus?
Factors
- Stage of pregnancy during exposure, i.e. NSAIDs (B>D)
- Route of administration (IV vs. something not systemically absorbed)
- Dose, duration, etc.
Effects
- Destruction of fetus
- Structural anomalies
- Growth retardation
- CNS abnormalities
NSAIDs
- Category D in 3rd trimester
- Safe early on in pregnancy, but in third trimester, might close ductus arteriosus too soon
How do you know if a drug will be transferred from mom to the fetus?
- The more lipid soluble a drug is, the more likely it will pass through placenta.
- Charged and more polar drugs are water soluble and less likely to pass through the placenta.
- Ion trapping – fetal pH lower than mother. Something with no charge and lipophillic can cross placenta, but becomes negatively charged so it can’t diffuse back out.
Molecular weight (daltons) mw = 250 – 500 – very easily crosses mw = 500 – 1000 – easily crosses mw = >1000 – very poor Low the MW, the more likely it is to cross the placenta.
Protein Binding - More drug bound by serum proteins, the less that’s available to go cross placenta.
If a protein binds and kicks the drug off, then there’s more free drug to go to placenta.
How do you protect fetus from exposure to drugs?
2 main mechanisms protect fetus from drugs in maternal circulation:
Placental function:
- Semipermeable barrier, prevents things from crossing.
- Limited drug metabolism by placenta.
Drugs enter the fetus through the umbilical vein:
- 40-60% of the umbilical blood flow enter into the fetal liver
- Liver has enzymes to metabolize drugs.
Category A
A : Controlled studies in women fail to demonstrate risk in fetus during first trimester; fetal harm remote.
SAFE to use in pregnancy.
- Tylenol
- Folic acid
- Vitamins
Category B
Animal studies do not indicate risk to fetus and there have been no controlled studies in human women.
Animal studies have indicated risk, but human studies failed to demonstrate risk.
- NSAIDs in early pregnancy
- Zofran
Category C
C : Animal studies indicate risk and no adequate controlled human studies; risk vs. benefit
Not enough studies to say if the drug is okay or not
-Opioids?
Category D
D : Positive evidence of fetal risk but there may be certain situations in which benefits outweigh risk.
Patient might die if they don’t take the drug.
-Warfarin
Category X
X : There is definite fetal risk and the risk outweighs any benefit in pregnant women: CONTRAINDICATED.
-Acutane
How is drug transferred in breast milk?
General principles
Similar characteristics apply to transfer in breast milk as a placental transfer.
- Lipid solubility: high lipid solubility has easier transfer.
- Hind milk higher lipid content. ~produced towards beginning of lactation; concentrated, high fat milk.
- Charge - Ion trapping based on pH of milk vs. mom.
- Molecular size
- Protein binding
What additional factors influence how much drug can be transferred into breast milk?
-Time since delivery, i.e. initial post birth period there’s large gaps in mammary alveolar cells, which allow larger drugs to go through (close within 2 weeks postpartum, less transfer).
- Major determinant is maternal serum concentration
- i.e. Higher drug conc. in blood stream = more can transmit to milk.
- May be able to strategically schedule feedings for mom to have exposure without exposing the baby.
-pH of breast milk – 6.35 – 7.67: acidic is more likely to have ion trapping.
Pregnancy Label Changes
- Old nomenclature was not useful to assess risk, i.e. Cat C.
- Updates include reproductive risks – contraception, pregnancy testing, etc.
NEW LABELING:
- Pregnancy (L&D)
- Lactation
- Females and Males of Reproductive Potential (i.e. acutane)