Prescribing in pregnancy Flashcards
What drugs cross the placenta?
Most drugs, except large molecular weight drugs e.g. heparin. Small, lipid-soluble drugs cross more quickly.
What may affect absorption of drugs?
Morning sickness
What may affect distribution in pregnancy?
Increased plasma volume and fat stores, volume of distribution increases.
What affects metabolism of drugs in pregnancy?
Decreased protein binding, increased free drug due to lower albumin levels.
Increased liver metabolism of some drugs.
What affects the elimination of drugs in pregnancy?
Renal excretion increases, increased GFR
What are the changes to pharmacodynamics in pregnancy?
No significant changes in pregnancy.
May be more sensitive to some drugs, hypotension with antihypertensives in 2nd trimester.
What should be given 3 months prior to conception and up to 3 months after conception?
Folic acid 400ug
What major process happens in first trimester?
Organogenesis
What is the period of greatest teratogenic risk?
4th-11th week
What general guidance should be given in 1st trimester of pregnancy?
avoid drugs if at all possible unless maternal benefit outweighs risk to foetus
What are the adverse affects of ACE inhibitors/ ARBs
Renal hypoplasia
What are the adverse affects of androgens
Virilisation of female foetus
What are the adverse affects of anti-epileptics
Cardiac, facial, limb, neural tube defects
What are the adverse affects of cytotoxics
Multiple defects, abortion
What are the adverse affects of lithium
Cardiovascular defects
What are the adverse affects of methotrexate
Skeletal defects
What are the adverse affects of retinoids
Ear, cardiovascular or skeletal defects
What are the adverse affects of warfarin
Limb and facial defects
What is the major process that can be impacted in the 2nd and 3rd trimester
Growth of foetus
Functional development; intellectual impairment and behavioural abnormalities
What are the adverse effects on labour?
- progress of labour
- adaptation of foetal circulation (premature closure of ductus arteriosus)
- suppression of foetal systems (opiates- respiratory depression)
- bleeding (warfarin)
What drugs can have adverse effects on baby after delivery?
Opiates, SSRI- withdrawal syndrome, sedation