Drugs in Pregnancy Lecture PDF Flashcards
Drug therapy in pregnancy requires benefits of treatments outweighing risks for…
….both mother and fetus
drug characteristics and placental transfer
-increases ease at which a substance can cross into fetal circulation, polar molecules depend more on maternal fetal gradient and molecular weight affects transfer rate
Metabolism within the placenta
Several types of reactions occur in placental tissue but in large enough concentrations can still cause leaking over into fetal circulation, also possible placenta may produce toxic metabolites and enhance toxicity
How are fetal cardiac arrhythmias handled?
Antiarrhythmic drugs given to mother for treatment of the fetus
Predictable toxic drug rxns in the fetus (5)
- opioids (neonatal withdrawal syndrome)
- ACE inhibitors/ARB’s/Aliskiren (tekturna) (signifcant renal damage in fetus)
- NSAIDS (contraindicated in 3rd trimester because they inhibit labor and prolong pregnancy)
- DES (delayed effects increased risk for adenocarcinoma after puberty)
- retinol analogues (brain, heart, and face defects)
Indocin use in infants
Close a patent ductus arteriosus
Taratogenesis
Malformations including distortions of behavioral and biochemical abnormalities
Preimplantation/presomite period
The All or nothing period from conception to week 2 where teratogens act in either complete abortion or have no consequence
Embryonic period
First trimester, when organogenesis occurs, teratogen exposure can lead to gross malformations so mothers must especially avoid during this period
Fetal period
2nd and 3rd trimester, teratogen exposure disrupts function rather than gross anatomy such as brain development resulting in learning deficits or behavioral abnormalities
Why are human teratogens extremely difficult to identify? (5)
- incidence of congenital anomalies is generally low
- cannot test on pregnant women
- effects may be delayed
- behavioral effects are difficult to document
- often species dependent
Lack of proof of teratogenicity does not mean…
….a drug is safe
Category A-X drugs
A are least dangerous, controlled studies have failed to demonstrate risk to fetus, then B is pretty safe, C could go either way, D is a lot worse but can be used if benefits outweigh risks, X are absolute no use because risk clearly outweighs benefit
New FDA Pregnancy and Lactation Labeling Rule (PLLR)
Phases out pregnancy risk categories and make it obsolete, has 3 sections for labeling (pregnancy, lactation, females and males of reproductive potential)
Responding to teratogen exposure
- Determine when drug was taken and when pregnancy began
- if exposure occurred during organogenesis, consult reference to determine type of malformation expected (if severe consider termination of pregnancy, if minor may be correctabe)
