Prescribing in Pregnancy Flashcards
How common is medication use during pregnancy?
> 90% of women take drugs during pregnancy = painkillers (12%), antibiotics (11%), antacids (8%), folic acid and iron
What are some common self-medicated drugs taken during pregnancy?
NSAIDs, St John’s wart, herbal preparations
What drugs won’t cross the placenta?
Drugs with large molecular weight
What actions encompass pharmacokinetics?
Absorption, distribution, metabolism and elimination
How may pregnancy affect absorption of drugs?
Morning sickness may affect absorption
How can pregnancy affect pharmacokinetics?
Decreased protein binding = increased free drug
Increased liver metabolism of some drugs
Elimination of renally excreted drugs increases
How does pregnancy increase volume of distribution?
Increases plasma volume and fat stores
Does pregnancy alter pharmacodynamics?
No = no significant change
How is prescribing managed pre-pregnancy?
Folic acid = 400mcg daily for 3 months before conception and for 1st three months of pregnancy
Counselling for chronic conditions
Optimise therapy to choose safest drug
What does the first trimester carry risk of?
Risk of early miscarriage and period of greatest teratogenic risk = avoid drugs if possible
When is the period of greatest teratogenic risk?
4th - 11th weeks gestation
What are some common drugs that are teratogenic?
ACE inhibitors = renal hypoplasia
Androgens = virilisation of female foetus
Anti-epileptics = cardiac/facial/limb/neural tube defects
Cytotoxics = multiple defects, abortion
Lithium = CV defects Methotrexate = skeletal defects
Warfarin = limb and facial defects
What normally occurs in the second and third trimesters?
Growth of foetus and functional development
What effects can drugs have on the foetus in the second and third trimesters?
Intellectual impairment and behavioural abnormalities
Toxic effects on foetal tissue
How can drugs have an adverse effect on labour?
Progress of labour, respiratory depression, bleeding
Adaption of foetal circulation = premature closure of ductus arteriosus
What adverse effects can drugs have on the baby after delivery?
Withdrawal syndrome or sedation
What were the negative effects of diethlystilbestrol?
Urological malignancies in boys
Vaginal adenocarcinomas in girls aged 15-20
What does untreated epilepsy carry a risk of?
Untreated epilepsy has higher incidence of congenital malformations than in women with treated epilepsy
How may pregnancy impact epilepsy?
May increase seizures (10%) = changes in plasma concentration of drugs (persistent vomiting, increased clearance)
What are frequent seizures during pregnancy associated with?
Lower verbal IQ, hypoxia, bradycardia, antenatal death and maternal death
What do anti-epileptic drugs increase the risk of?
Congenital malformations = 20-30% risk if on 4 drugs, monotherapy is preferred as lower risk
What anti-epileptics should be stopped during pregnancy?
Valproate and phenytoin
How much folic acid should be prescribed to women with epilepsy during pregnancy?
5mg daily
Is insulin safe to take during pregnancy?
Yes = may need to change dose
What does poor diabetic control during pregnancy increase the risk of?
Congenital malformations and intra-uterine death
What diabetic medication must be stopped during pregnancy?
Sulfonylureas = switch to insulin
What happens to blood pressure during the second trimester?
It falls
What drugs should be used to treat hypertension during pregnancy?
Labetalol, methyldopa or nifedipine MR
What anti-hypertensives should be avoided during pregnancy?
Avoid ACE inhibitors and ARBs
Beta blockers may inhibit foetal growth in late pregnancy
What are some common acute problems that occur during pregnancy and their preferred treatment?
Nausea and vomiting = cyclizine safest
Pain = paracetamol Heartburn = antacids
UTI = nitrofurantoin, cefalexin, trimethoprim if 3rd trimester
What is the leading cause of maternal death during pregnancy?
VTE = pregnancy increases risk of VTE by 10%
What are all women encouraged to do during pregnancy to reduce risk of VTE?
Mobilise and stay adequately hydrated
What should women at high risk of VTE be prescribed?
Thromboprophylaxis with LMWH = give at delivery and up to 7 days post partum
What are the risk factors for VTE?
Obesity, age >35, smoking, parity >3, previous DVT, C-section = considered high risk of 2 or more risk factors
How should DVT or PE during pregnancy be treated?
Using therapeutic dose of LMWH
Why should warfarin be avoided during pregnancy?
Teratogenic in early pregnancy
Carries risk of haemorrhage during delivery
Do drugs tend to enter breastmilk?
Yes = most drugs enter breastmilk, especially small molecules and lipophilic drugs
What can affect the amount of drug a baby receives through breastmilk?
Feeding pattern = longer feeds have higher amounts of fat soluble drugs in milk
Why may drugs accumulate in a baby?
They have immature metabolisms
What is an example of a drug that is actively concentrated in breastmilk?
Phenobarbitone = causes suckling difficulties
What are some drugs that can cause problems when they are transferred via breastmilk?
Amiodarone = neonatal hypothyroidism Cytotoxics = bone marrow suppression Benzodiazepines = drowsiness Bromocriptine = supresses lactation
What are some effects of drugs on babies?
Tetracycline = staining of bones and teeth Phenytoin = cleft lip and palate Valproate = neural tube defects (spina bifida, anencephaly)
What are the facial features caused by foetal alcohol syndrome?
Short palpebral fissures, flat midface, short nose, indistinct philtrum, thin upper lip, epicanthal folds, low nasal bridge
