Prescribing in Pregnancy Flashcards
All of the organs in a foetus have pretty much formed by what week of pregnancy?
week 11
When do women who are pregnant usually get their first scan?
12 weeks
detailed scan occurs at 20 weeks
What drug previously used as an anti-emetic for morning sickness is now known to have caused in utero deaths and also congenital defects?
Thalidomide
- caused mainly limb defects
What evidence do we have for drugs that ARE used in pregnancy?
- randomised clinical trials
- Anecdotal reports
- Circumstantial evidence of safe use
- Retrospective series where exposure has occurred
- Data extrapolated from animal studies
What do doctors prescribe to try and prevent pregnancy complications?
- Consider non-drug alternatives
e.g.
Physiotherapy instead of NSAIDs
CBT instead of antidepressants
If benefits outweigh risks to the mother, does a doctor usually prescribe in pregnancy?
Yes BUT a lot of drugs are unlicensed for pregnancy use so they are prescribing “off license”
Most women are reluctant to take drugs during pregnancy and most doctors are reluctant to prescribe drugs to pregnant women. TRUE/FALSE?
TRUE
If a drug is prescribed to a pregnant woman, how should the dosage and course be adapted?
Minimum effective dose for the shortest amount of time
What percentage of women DO take some form of drug during their pregnancy, and what type of drugs are most commonly taken?
Painkillers ~12%
Antibiotics ~11%
Antacids ~8%
(Also folic acid and iron)
What medications over the counter should not be taken by women who are pregnant?
NSAIDs
St John’s wort
Other herbal preparations
What type of drugs are known to cross the placenta?
- Almost all drugs cross placenta
- Especially small, lipid-soluble drugs (Cross quickly)
- Large molecular weight drugs DON’T CROSS (Heparin)
What are the main principles of pharmacokinetics and how does pregnancy affect these?
Absorption
- morning sickness affects this
Distribution
- Increased plasma vol. and fat stores for volume distribution
- Decreased protein binding => increased free drug
Metabolism
- Increased liver metabolism of some drugs
e. g. Phenytoin
Elimination
- Elimination of renally excreted drugs increases
It is thought pregnant women might be slightly more sensitive to some drugs during pregnancy. GIve an example of this?
BP reduces in second trimester of pregnancy
=> more sensitive to anti-hypertensives in 2nd trimester
What pre-conception counselling would ideally be given before patients get pregnant?
- Stop smoking and drinking alcohol
- Folic acid 400mcg daily for 3 months prior and first 3 months of pregnancy
- Counselling on their chronic conditions
e. g. Epilepsy, diabetes, hypertension
The period with the greatest risk of teratogenicity is during what weeks in the 1st semester of pregnancy?
Period of greatest teratogenic risk
4th -11th week
=> Avoid drugs if at all possible during this period
What drugs are teratogenic and what effects do they cause?
ACE inhibitors/ARB = Renal hypoplasia
Antiepileptics = Cardiac, facial, limb, neural tube defects
Lithium = Cardiovascular defects
Retinoids = Ear, cardio, skeletal defects
Warfarin = Limb and facial defects
What is the aim of the valproate pregnancy prevention programme?
Scheme where women of childbearing age have to sign to say they have been educated on the risks of using valproate if they were to get pregnant
How can some drugs affect the baby around term or at the time of labour?
- Affects progress of labour
- Adaptation of foetal circulation (Premature closure of ductus arteriosus)
- Suppression of foetal systems (Opiates – resp. depression)
- Bleeding (Warfarin)
How can drugs that the mother was on during pregnancy affect the baby even AFTER it is born?
- Withdrawal syndrome (opiates, SSRI)
- Sedation
What previous drug used for preventing miscarriage has been shown to have very late effects on babies born to these mothers?
Diethylstilbestrol
- children develop vaginal or urogenital adenocarcinoma in teenage years
Compliance in pregnancy is poor. TRUE/FALSE?
TRUE
- women avoid taking their asthma inhalers
- 20% of women discontinue antiepileptic medication
Women who receive no epilepsy treatment during pregnancy are still more likely to have a child born with congenital defects than those without epilepsy. TRUE/FALSE?
TRUE
=> untreated epilepsy in pregnancy can cause the mother to have seizures which may cause complications to the child
Why do seizures amongst females with epilepsy increase when they are pregnant?
- Non-compliance to meds in pregnancy
- Changes in plasma concentrations of drugs
(Due to vomiting from morning sickness OR Increased clearance)
What drug regime is normally preferred for pregnant patients with epilepsy and what drugs are commonly avoided?
- Monotherapy preferred (as opposed to multiple agents)
- Avoid valproate, phenytoin
- ALSO GIVE Folic acid 5mg daily
What percentage of women taking AED’s have children born with congenital malformations?
96% = No MAJOR congenital malformations (heart defects etc)
=>Benefits of treatment outweigh risks in most cases
How is diabetes commonly managed in pregnant women?
- insulin requirements change during pregnancy
=> many women put on insulin injections - Sulphonylureas removed as not safe
- Poor control increases risk of congenital malformations and intra-uterine death
If hypertension needs treated in pregnancy, what agents can be used for this?
Labetalol
Methyldopa
(Nifedipine MR - “off license”)
What anti-hypertensives should be avoided in pregnancy?
- Avoid ACE inhibitors / ARB
- Beta blockers may inhibit foetal growth in late pregnancy
What common acute problems do patients often need medication for during pregnancy?
- N+V = Cyclizine (safest)
- UTI (local guidelines) => Nitrofurantoin, (3rd trimester = trimethoprim)
- Pain => Paracetamol
- Heartburn = Antacids
How should VTE be prevented in pregnancy?
ALL women - pregnant/ labour/ puerperium
- be encouraged to mobilise
- be adequately hydrated
Those with 2 significant risk factors (BMI, smoking, age etc)
=> thromboprophylaxis with LMWH at delivery and up to 7 days post-partum
Why is LMWH used for thromboprophylaxis in pregnancy and not warfarin?
Warfarin in early pregnancy
= Teratogenic
Warfarin in late pregnancy
= Risk of haemorrhage during delivery
What drugs can enter the breast milk if a baby is breastfeeding?
Most drugs enter breast milk, especially:
- Small molecules
- Fat soluble (lipophilic) drugs
BUT very few enter in sufficient quantities to cause a problem
Why can the length of a feed cause potentially more problems?
Foremilk – protein rich
Hindmilk – higher fat content
Longer feeds => higher amounts of fat soluble drugs in milk that baby receives
Why may drugs from breastmilk accumulate in a newborn?
immature metabolism
What drugs cause issues if transferred through breastmilk?
Phenobarbitone – suckling difficulties Amiodarone – neonatal hypothyroidism Cytotoxics – bone marrow suppression Benzodiazepines – drowsiness Bromocriptine – suppresses lactation
Where can extra information of prescribing in pregnancy be found?
BNF:
- Guidance on Prescribing chapter at front
- Specific prescribing information listed under each drug
UK Teratology Information Service
UKDrugs in Lactation Advisory service
When should you consider starting pregnancy specific anti-hypertensives if a patients BP is high before conceiving?
- Can wait until after BP dip in 2nd trimester
OR can start before pregnant
How is a DVT or PE treated during pregnancy?
LMWH injections that the patient can self administer
- if PE then patient may need to stay in hospital until more stable
What type of antibiotics can cause grey teeth staining of the baby if taken during pregnancy?
Tetracyclines (e.g. doxycycline)
What “drug” if taken during pregnancy can cause multiple facial changes including a flattened face and nose?
Alcohol
=> Foetal Alcohol Syndrome
What old anti-epileptic was known to cause cleft-lip and palate if taken during pregnancy?
Phenytoin
What teratogenic side effects are common with taking sodium valproate during pregnancy?
Spina Bifida
Anencephaly
(NEURAL TUBE defects)
