Prescribing in Pregnancy Flashcards
What percentage of women will take drugs in pregnancy?
> 90%
What drugs are taken most frequently in pregnancy?
Painkillers
Antibiotics
Antacids
Will drugs cross the placenta?
Yes; except large molecular weight such as heparin
Small, lipid soluble drugs pass quicker
How is absorption of drugs affected in pregnancy?
May be affected by things like morning sickness
How distribution of drugs affected in pregnancy?
Increased plasma volume and fat stores
Volume of distribution increases
Decreased protein binding and therefore increased free drug
How is the metabolism of drugs affected in pregnancy?
Increased liver metabolism e.g. phenytoin
How is elimination of drugs affected in pregnancy?
Increased GFR
Are pharmacodynamics affected in pregnancy?
No significant changes
Pregnant women may be more sensitive to some drugs
What needs to be considered when women are preconception?
Are they pregnant? Are they planning a pregnancy? Could they become pregnant? Counselling re chronic conditions; epilepsy, diabetes, hypertx Optimise therapy to choose safest drug Review whether drug therapy necessary
How much folic acid should be taken pre and post conception?
400 mcg 3 months prior and first 3 months of pregnancy
What are the risks of prescribing in 1st trimester?
Risk of early miscarriage
Organogenesis
Avoid drugs if at all possible unless maternal benefit outweighs risk to foetus
What is the period of greater teratogenic risk?
4-11 week
List of teratogenic drugs
ACEi Androgens Antiepileptics cytotoxics Lithium Methotrexate Retinoids Warfarin
What is the abnormality assoc with ACEi in pregnancy?
Renal hypoplasia
What is the abnormality assoc with androgens in pregnancy?
Virilisation of female foetus
What is the abnormality assoc with antiepileptics in pregnancy?
Cardiac, facial, limb and neural tube defects
What is the abnormality assoc with cytotoxics in pregnancy?
Multiple defects
Abortion
What is the abnormality assoc with lithium?
CV defects
What is the abnormality assoc with methotrexate?
Skeletal defects
What is the abnormality assoc with retinoids?
Ear, cv, skeletal defects
What is the abnormality assoc with warfarin?
Limb and facial defects
What are the risks in the 2nd and 3rd trimester in terms of prescribing?
Growth of foetus
Functional development; intellectual, behavioural
Toxic effects on foetal tissue
What effects can prescribing have around term?
Adverse effects on labour; progres of labour, adaptation of foetal circulation (premature closure of ductus with NSAIDs)
Suppression of foetal systems (opiates)
Bleeding (Warfarin = catastrophic)
What adverse effects can prescribing have on the baby after delivery?
Withdrawal syndrome; Opiates, SSRI
Sedation
What effects did diethylstilbestrol have on children?
Vaginal adenocarcinomas in girls aged 15-20
Urological malignancy in boys
What can lead to the 10% increased in seizures seen in epileptic women whilst pregnant?
Non-compliance
Changes in plasma conc of drug; persistent vomiting, increased clearance
What are frequent seizures in pregnancy associated with?
Lower verbal IQ Hypoxia Bradycardia Antenatal death Maternal death
Which antiepileptics should be avoided in pregnancy?
Valproate
Phenytoin
How much folic acid should be given to epileptic women whilst pregnant?
5mg daily
What % of babies born to women taking epileptics have a major congenital malformation?
4%
96% do not
Is insulin safe in pregnancy?
Yes
What is the risk associated with poor diabetic control in pregnancy?
Increases risk of congenital malformation and intrauterine death
Are sulfonylureas safe in pregnancy?
No; convert to insulin
What can be used to treat hypertension in pregnancy?
Labetalol
Methyldopa; assoc with depression
Nifedipine
AVOID ACEI
What risk is assoc with beta blockers in pregnancy?
Can inhibit foetal growth in late pregnancy
How is N+V tx in pregnancy?
Cyclizine
How are UTIs tx in pregnancy?
Nitrofurantoin in 1st and 2nd trimester
Trimethoprim in 3rd trim
How is pain tx in pregnancy?
Paracetamol
How is heartburn tx in pregnancy?
Antacids
What is the risk of VTE in pregnancy?
10 fold increase
Leading cause of maternal death in pregnancy
What advice is given to all pregnant women to prevent VTE?
Mobilise
Adequate hydration
Who should receive LMWH prophylaxis for VTE in pregnancy?
2 or more risk factors; age >35, obesity, smoking, para >3, previous DVT, C-section
When should high risk mothers receive LMWH?
Delivery
7 days post-partum
How is VTE tx in pregnancy?
Therapeutic dose of LMWH
AVOID WARFARIN:
1st trim; teratogenic
3rd trim; hemorrhage in delivery
Do drugs enter the breast milk?
Most but especially small and lipophilic molecules
Tend to enter in small quantities
How can feeding patterns affect drug distribution in breast feeding?
Foremilk; protein rich
Hindmilk; higher fat content
Longer feeds, higher amounts of fat soluble drugs in milk
What will amiodarone in breast milk result in?
Neonatal hypothyroidism
What will cytotoxics in breast milk result in?
Bone marrow suppression
What will BZD in breast milk result in?
Drowsiness
What will bromocriptine in breast milk result in?
Suppresses lactation
Which antibiotic given in pregnancy or early childhood results in brown teeth staining?
Tetracycline
Which drug taken in excess can cause; short palpebral fissure, flat midface, short nose, thin upper lip?
FAS
Which antiepileptic is assoc with a cleft lip and palate?
Phenytoin
Which antiepileptic is assoc with spina bifida and anencephaly?
Valproate
