15 - Pharmacology in Pregnancy & Breastfeeding Flashcards
% of women of child-bearing age take medications?
80%
name 4 common conditions women take medications for?
hypertension
epilepsy
asthma
mental health disorders
what are the 4 factors involved in the kinetic processes?
absorption
distribution
excretion
metabolism (elimination)
give 3 reasons why oral route is often difficult for pregnant women?
morning sickness
decreased gastric emptying
decreased gut motility
describe 2 other routes for pregnant women to use?
intramuscular
inhalation
why do intramuscular drugs have increased absorption for pregnant women?
blood flow is increased
why do inhaled drugs have increased absorption for pregnant women?
increased cardiac output and decreased tidal volume
what 2 factors result in change in distribution of drugs?
increased plasma volume
increased fat
what results in decreased relative amount of plasma proteins?
increased dilution of plasma
what is the effect of progesterone & oestrogen on metabolism?
they inhibit OR induce liver P450 enzymes
therefore increase/ decrease metabolism
describe pregnancy’s effects on GFR?
GFR increases in pregnancy by 50%
what is the result on this change of GFR during pregnancy?
GFR increases
therefore, increased excretion of drugs
do drugs cross the placenta?
MOST of them do
name 4 factors affecting a drugs’ ability to cross the placenta?
drug’s physiochemical properties
rate @ which drug crosses placenta
duration of drug exposure
stage of placental & foetal development
3 factors which affect placental transfer?
molecular weight (small - cross easily)
polarity (unionised - cross easily)
lipid solubility (lipid soluble - cross easily)
what action might the placenta have on some drugs?
it may metabolise them
why is distribution in foetus different to that of an adult?
i.e. why is there more free drug available
less protein binding
less fat
increased blood flow to brain
why is foetus enzyme activity decreased?
foetus exhibits different p450 enzymes
metabolism and enzyme activity increases with gestation
describe foetal excretion?
foetus excretes drug into amniotic fluid - foetus then swallows this - therefore RECIRCULATION
what does the foetus’ excretion method then cause?
accumulation of substances in amniotic fluid
what is the result of the placenta not functioning at delivery?
issues with excretory function
most drugs have little data to understand their dosing - name 4 groups of medications which are relatively understood?
anti-convulsants
anti-hypertensives
analgesics
antibacterials
when is the highest risk of teratogenicity during pregnancy and why?
1st trimester - @ 3-8 weeks - organogenesis
name 3 mechanisms for teratogenicity?
folate antagonism
neural crest cell disruption
oxidative stress
name 3 possible issues associated with fetotoxicity?
growth retardation
structural malformations
foetal death
name 2 types of medications and possible effects of these on the foetus?
ACEIs & ARBs - renal dysfunction, growth retardation
name 5 principles of prescribing for women of child-bearing age?
1 - consider possibility of pregnancy
2 - warn women of risks
3 - advise women with other conditions to attend before planning pregnancy
4 - discuss contraception
5 - do not prescribe without contraception if possible
name 8 principles of prescribing during pregnancy?
1 - try non-pharmacological treatment first
2 - use drug with best safety record
3 - check SPC for up to date info
4 - use lowest effective dose
5 - use drug for shortest possible time (and intermittent)
6 - avoid 1st 10 weeks if possible
7 - consider stopping/ reducing dose before delivery
8 - never under-treat a disease which is harmful
what advice should be given re herbal remedies during breast feeding?
avoid them
which herbal medications are hepatotoxic?
those with pyrrolizidine alkaloids
