Pharmacology in Pregnancy Flashcards
what changes occur in pregnancy that can affect absorption?
> morning sickness > increased gastric emptying > increased gut motility > increased blood flow (increased absorption) > increased cardiac output > decreased tidal volume
what changes occur in pregnancy that can affect distribution?
> increased plasma volume
increased fat
decreased amount if plasma proteins due to dilution
what changes in pregnancy affect metabolism?
> oestrogen and progesterone can induce or inhibit liver p450 enzymes
how does an increase in GFR in pregnancy effect drug secretion?
> there is increased secretion of many drugs
> there is a decrease in plasma concentration so a decrease in renally cleared drugs
what pharmacodynamic changes can occur in pregnancy?
there may be a change in the site or action and the receptor response so efficacy and adverse effects may change
what are the principles of prescribing in pregnancy?
> try non-pharma first
use for shortest time period and intermittently if possible
use lowest effective dose
don’t under treat the disease harmful to the fetus
consider stopping or reducing prior to the pregnancy
avoid in 1st 10 weeks
use drugs with best safety record
what differences in the foetus affect pharmacokinetics?
> less protein binding so more drug available
little fat
relatively more blood flow to the brain
less enzyme activity
different izoenzymes
amniotic fluid allows accumulation and recirculation
what drugs should be avoided in breast feeding?
> cytotoxics > immunoosupressants > anticonvulsants > opiates > amiodarone > lithium > radioidine
what are the principles of prescribing in breast feeding?
> avoid unnecessary drug use
licenced safe for <2yrs probs. safe for breast feeding
choose drug with pharmacokinetic properties to reduce infant exposure (high protein bound)
what materials pass form mother to foetus?
> glucose > O2 > lipids > ions > viruses >antibodies > vitamins
what affects the materials exchanged through the placenta?
> size
electrical charge (non-ionised cross more easily)
lipophilicity
protein binding
what materials are passed from the foetus to the mother?
> urea
> CO2
when is the biggest risk of teratogenicity?
in the first trimester during organogenesis
what are the mechanisms of teratogenicity?
> neural crest cell disruption > folate antagonism > endocrine disruption > oxidative stress > vascular disruption
name some teratogens
> anticonvulsants > ACE inhibitors > alcohol > retinoids > NSAIDS > anticoagulants
what teratogenic effect does valproate have?
neural tube defect
what are the teratogenic effects of NSAIDS?
premature closure of the ductus arteriosus
what are the teratogenic effects of warfarin?
> haemorrhage
> CNS and skeletal effects
what is fetotoxicity?
drugs having toxic effects on the foetus later on
what problems can arise in fetotoxicity?
> foetal death > structural malformations > growth retardation > functional impairment > carcinogenesis
what are the different categories of fetotoxicity in drugs?
A. controlled studies show no risk B. animal studies show no risk C. no studies or data D. evidence of risk but benefit may outweigh X. no benefit and proven risk
what is enzyme mediated teratogenesis?
drugs may interact with specific receptors and enzymes of foetal development
what drug causes neural crest cell disruption?
retinoid drugs
what problems arise from neural crest cell disruption?
> pharyngeal gland abnormalities > oesophageal atresia > ventricular septal defects > craniofacial malformations > aortic arch anomalies
