Obs and Gynae Flashcards
name 7 important prescribing considerations during pregnancy/breastfeeding
- Changes to the mother’s physiology
- drugs passing through placenta to foetus
- drugs passing through breast milk to baby
- less available licensed medications
- minimal evidence base
- patient/healthcare professional anxiety surrounding prescibing in pregnancy
- dose alterations required in pregnancy.
How does the CVS change in pregnancy?
increases in plasma volume, CO, stroke volume, HR.
Decreases in serum albumin conc, and serum colloid osmotic pressure.
increases in coagulation factors and fibrinogen
compression of the IVC by the uterus.
Results in hyperdynamic circulation.
What might you find on CVS examination in a pregnant woman?
bounding pulse, 3rd heart sound, systolic flow murmurs
What normal physiological ECG changes might you see in a pregnant woman?
Left axis deviation, ectopic beats, ST depression and flattening/inverted T waves in inferior and lateral leads.
what normal physiological blood test findings might you find in a pregnant woman?
dilutional anaemia, leukocytosis, low albumin
what happens to the GFR in pregnancy?
Increases due to increases in renal blood flow
what physiological changes do you get in the lungs in pregnant women?
increase in tidal volume and minute ventilation.
what physiological changes do you get to the GI system during pregnancy?
N&V, delayed gastric emptying (allows increased nutrient absorption but can result in constipation), prlonged small bowel transit time, Gastrointestinal reflux
How might GI changes in pregnancy affect drug absorption?
delayed gastric emptying nad prolonged transit time alters drug bioavailability, with prolonged time to reach peak levels after oral administration and an overall decrease in maximum conc achieved. N&V can also affect absorption
how might changes to the CVS during pregnancy affect drug distribution?
increased total body water/extraellular fluid increases volume of distribution of water-soluble drugs. this could necessitate a higher inital and maintenance dose of drugs to obtain therapeutic plasma concentrations. lipid-soluble drugs are also affected due to increased fat compartment stores.
with increasing plasma volume, there is an associated reduction in maternal plasma protein conc. decreased plasma albumin conc. leads to decreased protein binding and increases free fraction of the drug. this is impoartnat for drugs such as midazolam, digoxin, phenytoin, valproic acid. However, these effects may be off-set by changes in metabolism and elimination.
What effects do maternal changes have on distribution?
increased plasma volume - increased volume of distribution of water-soluble drugs, requires higher drug doses.
Reduction in plasma protein levels - decreased protein binding, increased free fraction of the drug
what physiological effects on the liver occur in pregnancy?
changes in oxidative liver enzymes, such as cytochrome P450
how might metabolism of drugs be affected in pregnancy?
altered cytochrome P450 activity in pregnancy (unchanged/increased/decreased), alters oral bioavailability and hepatic elimination.
how is elimination of drugs affected during pregnancy?
incraesed renal blood flow and GFR means increased clearance, shorter half-lives of renal cleared drugs.
If clearance of lithium is doubled in the third trimester, how might the dose need to be adjusted?
higher dose will be required
what is the background risk of congenital malformationsi in pregnancy
2-3%
what is the background risk of congenital malformations in women with epilepsy who take AEDs during pregnancy?
4-10%
name 5 risks of using medications during pregnancy
- teratogenesis
- effects on growth and development
- effects on the neonate during delivery
- passage of drug through breast milk
- long term effects on IQ or behavioural problems
name 7 prescribing principles in pregnancy
- pre-pregnancy counselling
- risk vs benefit decision
- minimise drug use in first trimester
- small effective dose
- opt for ‘well-known’ meds
- monotherapy where possible
- consider non-drug options
- carefully monitor meds and their effects.
what is the daily recomended pre-conception dose of folic acid and for how long should it be prescribed?
400 micrograms daily up to 12wks gestation
what dose of foic acid is recommended for higher risk women during pregnancy?
5mg
name 3 AEDs with lower risks of malformations (2-5%)
lamotrigine, levetiracetam (Keppra), carbamazepine
name the AED with the higher risk of malformations (7-10%)
sodium valproate (Epilim)
What properties of a drug allow it to cross the placenta?
lipid-soluble drugs, or lipid soluble metabolites of some drugs
what is meant by complete transfer of a drug acorss teh placenta?
where drugs rapidly cross the placenta, equilibrating in maternal and fetal blood
what is meant by exceeding transfer of a drug across the placenta?
where drugs cross the placenta to reach greater concentrations in fetal compared to maternal blood
what is meant by incomplete transfer of a drug acorss the placenta?
where drugs incompletely cross the placenta resulting in higher conc in maternal compared with fetal blood
almost all drugs can pass freely through the placenta with the exception of what?
those with a molceular weight of >1kDa
give an example of a drug with molecular weight of >1kDa meaning it doesn’t cross the placenta
insulin, heparin
name 5 NICE recommendations for the management of pregnancy-induced nausea
reassurance and rest, avoidance of triggers, eating plain crackers in teh morning, eating bland, small, frequent meals, cold meals if nausea is smell-related, drink little and often, ginger, acupressure
what gestation does pregnancy induced N&V usually resolve by
16-20wks
name 4 antiemetic therapies that can be used first line for pregnancy-induced N&V
cyclizine, prochlorperazine, promethazine, chlorpromazine
name 3 second-line antiemetic therapies that can be used for pregnancy-induced N&V
metoclopramide, domperidone, ondansetron
if neither first or second line antiemetics have worked for pregnancy-induced N&V, what can be tried third line?
hydrocortisone
other than antiemetics, what additional treatmetn should be given in hyperemesis gravidarum
IV fluid rehydration with potassium supplementation, pabrinex/thiamine (if prolonged vomiting).
in severe cases may need enteral/parenteral feeding.
TOP is last resort.
What did thalidomide used to be used for?
immunomodulator initially used to treat pregnancy-related nausea
what effect did thalidomide have on babies?
phocomelia (where limb buds don’t form correctly). also deformities of ears, heart, kidneys.
high mortality rate (40%)
name 6 common teratogenic drugs or drug classes
ACEi Anti-thyroid drugs beta-blockers lithium methotrexate NSAIDs
what effects can ACEi have on the fetus
renal abnormalities, PDA, oligohydramnios
what effects does carbimazole have on a neonate?
neonatal hypothyroidism
what effects can beta blockers have on the fetus and newborn?
IUGR, neonatal hypoglycaemia, bradycardia
what teratogenic effect does lithium have?
cardiac defects (Ebstein’s anomaly - a congenital heart defect where the septal and posterior leaflets of the tricuspid valve are displaced towards the apex of the right ventricle of the heart.
what teratogenic effects does methotrexate have
medical termination, craniofacial defects, ear/kidney/lung defects, cardiac abnormalities
what effect can NSAIDs have after 30wks gestation?
premature closure of the ductus arteriosus, oligohydramnios, PPHN (persistent pulmonary HTN of the newborn)
what teratogenic effect does phenytoin have?
craniofacial abnormalities, growth/mental deficiency
what teratogenic effect do retinoids have?
CNS abnormalities, renal/ear/eye/parathyrdoi abnormalities between wks 4-10
what teratogenic effects does sodium valproate have?
neural tube defects
which trimester does sodium valproate cause teratogenic effects
1st trimester
what teratogenic effect do tetracyclines have?
tooth discolouration
what teratogenic effects do thiazide diuretics have?
electrolyte abnormalities, growth retardation
what teratogenic effects does warfarin have?
fetal warfarin syndrome, CNS defects/eye abnormalities, fetal/neonatal/placental hamorhage
what does fetal warfarin syndroem casue
results in abnormalities including low birth weight, slower growth, mental retardation, malformed bones, cartilage, joints, deafness, small head size.
which two antihypertensives tend to be used in pregnancy as they are considered safer?
labetalol or nifedipine
name 3 drugs that can cause genetic abnormalities in the sperm
methotrexate
azathioprine
mercaptopurine
how long does the manufacturer of antimetabolite drugs such as methotrexate advise delaying conception for due to genetic abnormalities it could cause in teh sperm?
6 months
why should amiodarone be avoided in breastfeeding mothers?
iodine content may cause neonatal hypothyroidism
why should aspirin be avoided in breastfeeding mothers?
theoretical risk of Reye’s syndrome
why should barbiturates be avoided in breastfeeding mothers?
drowsiness
why shoudl benzodiazepines be avoided in breastfeeding mothers?
lethargy
why should carbimazole be avoided in breastfeeding mothers?
hypothyroidism
why shoudl codeine be avoided in breastfeeding mothers?
risk of opiate overdose
why should COC pill be avoided in breastfeeding mothers?
may diminish milk supply and quantity
why should cytotoxic drugs be avoided in breastfeeding mothers?
immunosuppression and neutropaenia
why should dopamine agonists be avoided in breastfeeding mothers?
may suppress lactation
why shoudl ephedrine be avoided in breastfeeding mothers?
irritability
hwhy should tetracyclines be avoided in breastfeeding mothers?
risk of tooth discolouration
renal abnormalities in the newborn are named with which two drugs or drug classes?
ACEi and methotrexate
parathyroid abnormalities in the newborn are associated with which drug class?
retinoids
what antibiotics are first line for PID
Ceftriazone IM \+ Metronidazole BD 14/7 \+ Doxycycline BD 14/7
what is the definition of primary infertility?
not being able to conceive after 1yr of regular, unprotected intercourse
what is the definition of secondary infertility?
those who have conceived in teh past (irrespective of the outcome of the pregnancy be it miscarriage, termination, ectopic or normal delivery), but fail to do so again after regular unprotected intercourse for one yr
