Prescribing in pregnancy Flashcards
Give a few examples of ways in which prescribing drugs can be avoided in pregnancy ?
- Physio instead of NSAID’s
- CBT instead of anti-depressants
When should you prescribe drugs in pregnancy ?
If the benefit from prescribing the drug outweighs the risk
Why is careful documentation of drugs prescribed during pregnancy needed ?
Because most drugs are not licensed for use in pregnancy
What are the attitudes of most mothers & doctors to prescribing in pregnancy ?
Drs are reluctant to prescribe & women are reluctant to take drugs during pregnancy
What is pharmacokinetics ?
This is the study of the movement of drugs within the body i.e. what the body does to the drug after its taken
What are the 4 main componets of pharmacokinetics ?
- Absorption
- Distribution
- Metabolism
- Excretion
How is the absorption of drugs affected in pregnancy ?
It may be affected by morning sickness (may vomit after taking drug ==> not enough time for full dose to be absorbed)
How is the distribution of drugs affected during pregnancy ?
- Volume of distribution is increases - due to increased plasma volume & fat stores
- It also increases due to decreased protein binding resulting in increased free drug
How is the metabolism of drugs affected during pregnancy ?
There is increased liver metabolism of some (not all) drugs e.g. phenytoin ==> these drugs may have a shorter action time & are eliminated faster
How is the exrection of drugs affected during pregnancy ?
Elimination of renally excreted drugs increases due to the increased GFR during pregnancy
Due to the changes in pharmacokinetics during pregnancy what may you need to do with some drugs during pregnancy ?
May need to check concentrations and alter dose during pregnancy and after delivery e.g. Lithium, digoxin
Define pharmacodynamics
This is what a drug does to the body i.e. the biological effects & mechanism of action of a drug
Are there many changes to the pharmacodyanmics of a drug during pregnancy ?
No - except they may become more sensitive to some drugs during the 2nd trimester e.g. risk of hypotension with antihypertensives in 2nd trimester (think cause BP is dropping during this period)
What pre-conception management is required for chronic conditions?
- Counselling regarding chronic condition
- Aim to optimise theraputic control & choose the safest drugs
- Also review if drug therapy is needed
How is the risk of neural tubual defects (NTD) in a pregnancy assessed?
Couples are assessed as high-risk if:
- Either partner has a NTD, or had a previous pregnancy with a NTD or a family history of NTD’s
- The women is taking ant-epileptic drugs
- Women has coeliac disease or anyother malabsorptive state, diabetes, sickel cell anaemia, or thalassaemia
- Women with BMI ≥ 30
What should women considered at normal risk of a NTD pregnancy take?
400 micrograms of folic acid daily 3 months prior (12wks) & continue until 3 months into pregnancy
What should women considered at high risk of a NTD pregnancy take?
5mg of folic acid daily 3 months prior & continue until 3months of pregnancy
What is the risk of taking drugs during the 1st trimester (upto week 12+6) of pregnancy ?
There is a risk of early miscarriage ==> recommened to avoid drugs during this period unless maternal risks outweigh the benefits
What is the period of greatest teratogenic risk during pregnancy ?
The 4th to 11th week
Match the following teratogenic drugs to the potential problems they can cause:
- ACEi/ARB
- Anti-epileptics esp Na valproate
- Cytotoxics e.g. methotrexate, cyclophosphamide, azathioprine, rheumatoid arthritis drugs, cancer drugs, antibiotics etc
- Androgens e.g. testosterone
- Lithium
- Retinoids
- Methotrexate
- Warfarin
Causes renal hypoplasia, causes virilisation of female fetus, causes cardiac, facial, limb & NTDs, causes multiple defects, abortion, causes cardiac defects, causes skeletal defects, causes ear, CV & skeletal defects, causes limb & facial defects
- ACE inhibitors/ARB - Renal hypoplasia
- Androgens - Virilisation of female foetus
- Antiepileptics - Cardiac, facial, limb, neural tube defects
- Cytotoxics - Multiple defects, abortion
- Lithium - Cardiovascular defects
- Methotrexate - Skeletal defects
- Retinoids - Ear, cardiovascular, skeletal defects
- Warfarin - Limb and facial defects
How may drugs affect the fetus during the 2nd and 3rd trimesters ?
They may affect growth of the fetus, functional development (intellectual impairment, behavioural abnormalities) or have toxic effects on fetal tissue
How may drugs adversely affect labour ?
- Affect Progress of labour
- Adaptation of foetal circulation e.g. Premature closure of ductus arteriosus
- Suppression of foetal systems e.g. Opiates – respiratory depression
- Bleeding e.g. Warfarin
How may drugs adversley affect the baby after delivery ?
- Withdrawal syndrome e.g. from opiates, SSRI
- Sedation
How is the compliance of asthamatics and epileptics with their medication during pregnancy ?
- Many women avoid taking their asthma inhalers in pregnancy
- Up to 20% of women discontinue antiepileptic medication in pregnancy
The incidence of congenital malformations higher in untreated women with epilepsy than women without epilepsy - T or F?
True
How many epileptic women experience increase seizure frequency during pregnancy and why is this?
10%, due to:
- Non-compliance
- Changes in plasma concentrations of drugs caused by Persistent vomiting, Increased clearance
What are frequent seizures in epileptic pregnant women associated with ?
Lower verbal IQ in child, hypoxia, bradycardia, antenatal death, maternal death
Why is monotherapy preferred in pregnant epileptic women?
Because the risk of congenital malformations increases as the number of epileptic drugs increases e.g. when on 4 it is as high as 20-30%
What 2 anti-epileptic drugs should be avoided and why?
- Na valproate - due to risk of NTD’s
- Phenytoin - due to greater risk of lots of defects
What percentage of babies born from women taking anti-epileptic medications will not have major congenital malformations ?
96%
The benefits of epilepsy treatment outweigh the risks of no treatment during pregnancy in general - T or F?
True
What are the only 2 diabetic controlling drugs safe for use in pregnancy ?
Insulin & metformin
All others should be discontinued prior to pregnancy & insulin should be started
What is the treatment of diabetes during pregnancy ?
If managed on metformin with good stable BG prior to pregnancy then continue with its use in pregnancy, otherwise use insulin for every other scenario in pregnancy
What is the risk of poor diabetic control during pregnancy ?
Increases risk of congenital malformations & IUD
Which diabetic drug is especially not safe during pregnancy ?
Sulphonylureas
What anti-hypertensive drugs should be avoided during pregnancy ?
ACEi/ARB’s
Why is care taken especially in the 2nd trimester to not cause hypotension in those being treated for HTN?
because BP decreases upto a nadir at 22-24 weeks
What is the treatment of HTN in pregnancy ?
- 1st line = Labetalol (avoid in asthma)
- 2nd line = nifedipine (can give bad headaches) or methyldopa
- 3rd line = Hydralazine or doxazocin
What can beta-blockers do in late pregnancy ?
They may inhibit fetal growth (more worried about this with newer ones, hence labetalol is fine)
What is the treatment of nausea & vomiting in pregnancy ?
If required treat with cyclizine
What is the treatment of UTI’s during pregnancy ?
- 1st or 2nd trimester give nitrofuratoin
- 3rd trimester give trimethoprim
2nd line for any trimester is cefalexin
What is the treatment of heartburn during pregnancy ?
Antacids
Why is warfarin avoided during pregnancy and labour ?
It is teratogenic in early pregnancy & carries risk of haemorrhage in late pregnancy and delivery
Most drugs enter breast milk, especially Small molecules and Fat soluble (lipophilic) drugs. Few enter in sufficient quantities to cause a problem - T or F?
True
What drug when used when breastfeeding can result in suckling difficulties in the baby?
Phenobarbitone
What problems can amiodarone cause when used in pregnancy?
Neonatal hypothyroidism
What can cytotoxics cause when used in pregnancy ?
Bone marrow suppression
What can benzos cause when used in pregnancy ?
Drowsiness
What problem may Bromocriptine cause when used in pregnancy ?
It can suppress lactation
What drug is avoided in children < 8 and why ?
Tetracyclines because they can cause staining of bones & teeth
What malformations is phenytoin associated with when used in pregnancy ?
Cleft lip & palate
What malformations is Na valproate associated with when used in pregnancy ?
NTD’s e.g. spina bifida, ancephaly
