Pharmacology in Pregnancy + Breast Feeding Flashcards
What changes occur to oral drug absorption during pregnancy?
- More difficult (morning sickness)
- Decrease in gastric emptying and gut motility
What changes occur to intramuscular drug absorption during pregnancy?
Blood flow may be increased (increases absorption)
What changes occur to inhaled drug absorption during pregnancy?
Increase cardiac output and decreased tidal volume = increased absorption of inhaled drugs
What changes occur to drug distribution during pregnancy?
Increased distribution (inc plasma volume and fat)
What changes occur to drug metabolism during pregnancy?
Oestrogen and progesterone can induce/inhibit liver P450 enzymes (increasing/decreasing metabolism)
What changes occur to drug excretion during pregnancy?
GFR increased by about 50% so increased excretion of many drugs
What does placental transfer depend on?
- Molecular weight
- Polarity
- Lipid solubility
Where does the fetus excrete drugs into and why can this be a problem?
Excretes into amniotic fluid which fetus swallows so leads to recirculation and increased level of drug
What are the principles of prescribing for women of child bearing age?
- Always consider pregnancy
- Warn women of possible risks
- Advise women to attend before getting pregnant to optimise treatment of medical conditions
- Discuss contraception
- If necessary, do not prescribe without contraception
What are the principles of prescribing in pregnancy?
- Try use non-pharmacological treatments first
- Use the drug with best safety record
- Check SPC for most up to date info
- Use lowest effective dose
- Use for shortest possible time
- Avoid first 10 weeks of pregnancy if possible
- Consider stopping or reducing dose before delivery
What are the 2 major risks of drugs during pregnancy?
- Teratogenicity (first trimester)
- Fetotoxicity (second and third trimester)
What is the effect of drugs that cause folate antagonism (methotrexate, trimethoprim, sodium valproate etc) in the fetus?
Neural tube, oro-facial or limb defects
What drugs are associated with neural crest cell destruction?
Retinoids
What are the effects of neural crest cell disruption?
- Aortic arch abnormalities
- Ventricular septal defects
- Craniofacial malformations
- Oesophageal atresia
- Pharyngeal gland abnormalities
What effects are NSAIDs associated with in pregnancy?
Orofacial clefts and cardiac septal defects
