Prescribing in Pregnancy Flashcards
Do most drugs cross placenta?
Yes, except LMW drugs e.g. Heparin
What drugs cross more quickly than others?
Small, lipid soluble
How is absorption effected in pregnancy?
Morning sickness
How is distribution effected in pregnancy?
Volume of distribution increased due to increased PV and fat stores
Decreased protein binding, so increased free drug
How is metabolism effected in pregnancy?
Increased liver metabolism of some drugs e.g. phenytoin
How is elimination effected in pregnancy?
Elimination of renally excreted drugs increases- increased GFR
Are pharmacodynamics effected in pregnancy?
No significant changes- pregnant women can be more sensitive to some drugs e.g. hypotension with antihypertensives in 2T
What should be taken pre-conception?
Folic acid 400mcg daily for 3 months prior and first 3 months of pregnancy
Safest drug therapy for existing chronic conditions
When is the period of greatest teratogenic risk?
4th to 11th week
Describe drug use in 1T?
Avoid drugs if at all possible unless maternal benefit outweighs risk to fetus
What teratogenic effects can ACEI/ARBs have?
Renal hypoplasia
What teratogenic effects can androgens have?
Virilisation of female fetus
What teratogenic effects can antiepileptics have?
Cardiac, facial, limb, neural tube defects
What teratogenic effects can cytotoxics have?
Multiple defects, abortion
What teratogenic effects can lithium have?
CV defects
What teratogenic effects can methotrexate have?
Skeletal defects
What teratogenic effects can retinoids?
Ear, CV, skeletal defects
What teratogenic effects can warfarin have?
Limb and facial defects
What can opiates around term?
Respiratory depression
What can warfarin cause around term?
Bleeding
What did diethylstilbestrol cause?
Vaginal adenocarcinoma in girls aged 15-20yo whose mothers took drug
Urological malignancy in boys
Can untreated epilepsy lead to congenital malformations?
Yes- incidence higher than that of women without epilepsy
Why does pregnancy increase seizures in 10% of women?
Non-compliance
Changes in plasma concentrations of drugs: persistent vomiting, increased clearance
What are frequent seizures during pregnancy associated with?
Lower verbal IQ Hypoxia Bradycardia Antenatal death Maternal death
Do antiepileptics increase the risk of congenital malformations?
Yes- 20/30% risk if on 4 drugs, monotherapy preferred
Avoid valproate, phenytoin
(96% won’t have major malformations)
Are insulin and sulfonylureas safe during pregnancy?
Insulin yes, sulfonylureas no- switch to insulin
What does poor diabetic control increase the risk of?
Congenital malformations
IUD
Do diabetic requirements change during pregnancy?
Yes
What can beta blockers do in late pregnancy?
Inhibit fetal growth
How should N & V be treated in pregnancy?
Cyclizine
How should UTI be treated in pregnancy?
Nitrofurantoin, cephalexin (3T trimethoprim)
How should mild pain be treated in pregnancy?
Paracetamol
How should heartburn be treated in pregnancy?
Antacids
By how much does pregnancy increase the risk of VTE?
10x
What thromboprophylaxis for VTE should be used in pregnancy and by who?
LMWH at delivery and up to 7 days post partum if:
2 or more RFs e.g. obesity, >35yo, smoking, para >3, previous DVT, Caesarean delivery
How should suspected or established DVT or PE be treated?
Therapeutic dose of LMWH
Avoid warfarin in early pregnancy (teratogenic) and late pregnancy (risk of haemorrhage during delivery)
What drugs enter breast milk?
Most, especially small or fat soluble drugs
How can feeding patterns affect amounts of drugs in breastfeeding?
Foremik- protein rick
Hindmilk- higher fat content
Longer feeds, higher amounts of fat soluble drugs in milk
What drug is actively concentrated in breast milk?
Phenobarbitone- suckling difficulties
What can amiodarone cause when passed through breast milk?
Neonatal hypothyroidism
What can cytotoxics cause when passed through breast milk?
Bone marrow suppression
What can benzodiazepines cause when passed through breast milk?
Drowsiness
What can bromocriptine cause when passed through breast milk?
Suppresses lactation
Which antibiotic given during pregnancy or in early childhood can cause staining of bones and teeth?
Tetracycline- avoid in children up to 8yo
Which antiepileptic drug is particularly associated with cleft lip and palate?
Phenytoin
Which antiepileptic drug is particularly associated with neural tube defects such as spina bifida and anencephaly?
Valproate
