Pregnancy and Breastfeeding Flashcards
What common drugs are prescribed in pregnancy?
- For minor ailments: analgesics, antibiotics, migraine - strain on back, more prone to UTIs
- Pregnancy induced disorders: eg morning sickness
- Chronic problems: asthma, epilepsy, depression
Should drugs for chronic disorders be stopped?
No, disease may adversely affect pregnancy
What are some reasons a pregnant woman may stop copmplying with medications?
- doubt about drug use
- side effects
- disappearance of complaints for which drug was prescribed
What are some pre conception counselling points?
- recognise and address biomedical or behavioural issues that may pose a risk
- establish woman on prophylactic. drugs and immunisation
- ensure mother can make informed choices about therapeutic drugs
What is folic acid necessary for and what does deficiency cause?
- necessary for proper haematopoeisis
- deficiency leads to increased risk of neural tube defects
What is the risk of a NTD based on?
- either partner having a NTD, previous child with NTD, familt history of NTD
- woman taking anti-epileptic drug or diabetic
- BMI > 30kg/m2
If someone is at normal risk of NTD, how much folic acid should be prescribed?
400mcg daily until week 12 of pregnancy
How much folic acid should someone at high risk for NTD take?
5mg daily
What are some examples of enzymes inducers and how do they affect levonorgestrel?
- Antiepileptics - barbiturates, primidone, phenytoin, carbamazepine
- Anti-tuberculosis - rifampicin, rifabutin
- HIV medicines - ritonavir, efavirenz
- Antifungals - griseofulvin
- Herbal remedies containing St John’s Wort
Reduces plasma levonorgestrel con
What should women seeking emergency contraception be given?
Levonorgestrel: 1.5mg
If taking enzyme inducer: non-hormonal emergency contraceptive (copper intrauterine device) or double the dose to 3mg
How long does fetal development take?
40 weeks
What is a teratogen?
A substance, organisms, physical agents or deficiency capable of inducing abnormal structure of function such as:
- gross structural abnormalities
- functional deficiencies
- intrauterine growth restriction
- behavioural abberations
- demise
What is teratogenecity?
The potential for a drug to cause foetal malformations and affects the embryo 3-8 weeks after contraception.
These weeks are the period of highest risk as organ systems are formed
What % of birth defects do drugs account for?
2-3%
What can drugs during the 2nd and 3rd trimester affect?
growth (IUGR) and functional development or have toxic effects on tissues.
Adverse effects on neonate if given shortly before or during labour (eg diazepam). Mothers system metabolises drug, drug passes to baby
What should you consider when prescribing in pregnancy?
- assume all drugs cross placenta unless they have a high MW (eg heparins)
- avoid drugs in first trimester if possible
- avoid medicines known to be harmful
- only prescribe if benefit outweighs risk to foetus
What drugs should be avoided in the first trimester and what do they cause?
- Androgens - causes multiple congenital defects
- Lithium - cardiac defects
- Sodium valproate - NTDs
- Warfarin - multiple congenital defects
What drugs should be avoided in the second and third trimester and what do they cause?
- ACEi and ARBs - growth retardation, impaired neonatal blood pressure control and renal function
- NSAIDs and aspirin - prolongation of labour, hamehorrage
- Opiates and benzodiazepines - perinatal respiratory depression, withdrawal syndrome
- Tetracyclines - inhibits bonw growth
When may dose adjustments be affected?
- If renal elimination is increased eg enoxaparin
- If metabolism is increased eg lamotrigine
What information sources do we have for drugs in pregnancy?
- UKTIS
- Toxbase
How long should you breastfeed for and what are the benefits?
Until 6 months old.
- passage of maternal immunoglobulins - immunity
- reduced risk of allergy in infant
What does safety of a drug depend on whilst breastfeeding?
- passage of drug into breast milk
- subsequent absorption in infant
- ADR profile
- infant age
- infant co-morbidities
- effective clearance of drug
Who’s most at risk from exposure to drugs via breast milk?
- neonates
- premature infants
How can potential harm to infant be inferred?
- amount of active drug delivered in breatsmilk
- infant pharmacokinetics efficiency
- infant pharmacodynamics
What are the drug characteristics associated with reduced passage into breastmilk?
- high MW - insulin, heparins
- high protein binding - warfarin, NSAIDs
- low lipid solubility - loratadine
- lower pH - amoxicillin
Prescribing in breastfeeding counselling points?
- avoid unnecessary drug use
- benefit vs risk assessment
- avoid use of drugs known to cause toxicity
- choose regimen and route of administration which presents min amount of drug
- monitor infants closely
List drugs to avoid in breastfeeding and their adverse effect.
- Amiadarone - present in milk in significant amounts
- antithyroids - neonatal goitre and hypothyroidism
- benzodiazepine - present in milk
- Statins - high conc
- Lithium salts - present and risk of toxicity
What effects lactation?
- Drugs affecting dopamine activity. High dopamine leads to reduced milk.
- Early postpartum use of oestrogen may reduce milk volume - progesterone recommended as initial contraception
- some drugs may affect infants suckling reflex eg phenobarbital
