Pharmacology Flashcards
Are many drugs licensed for pregnancy
NO
Little evidence for almost every drug
Therefore most are prescribed off license
What are the alternative to prescribing in pregnancy
Consider non-drug alternatives
e.g. CBT for depression or physio instead of painkillers
What are some general principles for prescribing in pregnancy
Lowest effective dose for shortest period
If benefit outweighs risk, prescribe
Older drugs have better safety records
Which drugs can cross the placenta
Majority can
small lipid soluble drugs cross fastest
Except large molecular weight drugs like heparin
How can morning sickness affect medication
Absorption may be reduced
Particularly in Hyperemesis Gravidarum
What is the effect of pregnancy on renal excretion
Increased GFR early on in pregnancy – renally excreted drugs tend to be excreted even more.
Eliminated faster
Which drugs may pregnant women be more sensitive to
Hypertensive agents
Can lead to hypotension - particularly in the 2nd trimester
What medications should be started before pregnancy
Folic acid 400mcg daily for 3 months prior and first 3 months of pregnancy
This is to prevent neural tube defects
What is the period of greatest teratogenic risk
4th -11th week is the critical period
Avoid drugs if at all possible unless maternal benefit outweighs risk to foetus
List common drugs which are teratogenic
ACE inhibitors/ARB Androgens Antiepileptics Cytotoxics Lithium Methotrexate Retinoids Warfarin
What do common anti-epileptics do to a foetus
Cardiac, facial, limb, neural tube defects
Sodium valproate and phenytoin should be avoided
What does lithium do to a foetus
Cardiovascular defects
What effects can drugs have in the 2nd trimester
Can get intellectual impairment or behavioural abnormalities
It is the functional development that happens at this stage
What is the risk of giving non-steroidal around term
Can cause premature closure of DA
What effect do opiates have on a term baby
Opiates can cause respiratory depression and withdrawal syndrome later on
Which drugs can cause withdrawal syndromes in a new-born
Opiates
SSRIs
What happens to compliance in pregnancy
Often becomes poor as women stop taking it out of fear
Ideally discuss medication prior to conception so that its all safe and sorted
What are the risks of having seizures in pregnancy
Frequent seizures during pregnancy are associated with lower verbal IQ in child, hypoxia, bradycardia, antenatal death, maternal death
Therefore epileptics need to stay on some form of treatment
How much folic acid should be taken by a woman on anti-epileptics
5mg daily
What are the risks of uncontrolled diabetes in pregnancy
increases risk of congenital malformations and intra-uterine death
What diabetes drugs should be avoided in pregnancy
Sulfonylureas not safe
Convert patients to insulin
Which hypertension drugs should be used in pregnancy
If need to treat, use one of Labetalol or Methyldopa
Avoid ACE inhibitors / ARB
What naturally happens to BP in the second trimester
It falls
What is the safest drug to use to treat N and V in pregnancy
cyclizine
What should you use to treat UTIs in pregnancy
Nitrofurantoin, cefalexin, (3rd trimester – trimethoprim)
More prone to UTIs in pregnancy.
By how much does pregnancy increase the risk of VTE
10x
What is the leading cause of maternal death during pregnancy
VTE
Should pregnant women get VTE prophylaxis
YES - if high risk
Give them LMWH
How do you treat VTE in pregnancy
Treated with LMWH
Avoid warfarin in early pregnancy - teratogenic
Avoid in late pregnancy also - haemorrhage
Can drugs get into breastmilk
Most do - especially small, fat soluble ones
Few enter in sufficient quantities to cause a problem
Which drugs should be avoided in breastfeeding as they accumulate
Phenobarbitone Amiodarone Cytotoxics Benzos Bromocriptine
Which drugs would be used to manage hyperemesis
Anti-emetics like cyclizine or prochlorperazine
Ondasentron is very effective but not as much data so 2nd line only
Would use thiamine alongside (usually for 1 week)
Put up to 5mg folic acid
Omeprazole to protect stomach
Fragmin to reduce clot risk
What risk does ondansetron (anti-emetic) pose in pregnancy
Comes with a small risk of cleft palate in the foetus
Only used if nothing else works and benefit to mum outweighs cleft risk
If a woman is on steroids throughout pregnancy, what precaution must be taken in labour and post-natally
Their natural stress hormone response will be suppressed by steroid treatment so they will need IV steroids in labour
Would then need to wean them off after delivery
Which analgesics can be given in pregnancy
Paracetamol
Codeine (oral)
Stronger opiates such as morphine (ora or IV)
Just need to keep an eye on baby as they have had opiate exposure
Which analgesics cannot be given in pregnancy
Cannot give NSAIDS
In early pregnancy they have been associated with renal atresia
In third trimester they can cause premature DA closure
What caution must be taken when using biologics in pregnancy
Try and avoid in 3rd trimester as increased placental transfer so will affect foetus
Which antibiotics would be used to treat PID in pregnancy
Ceftriaxone, metronidazole and doxycycline
Which contraception can be put in place immediately after a C-section
Can insert a hormonal coil before closing
When does breastfeeding act as a contraceptive
Only if exclusively breastfeeding, not having periods and baby is under 6 months
What are the contraindications to placing a coil post C-section
- Only time you wouldn’t put in the coil is if she is septic or has massive fibroids
How soon after birth can mum start taking the combined pill
Can’t use combined pill when breastfeeding until at least 6 weeks post-natal
If not breastfeeding she would still need to wait 21 days due to clot risk
What factors can affect drug levels in pregnancy
Increased blood volume (50% by 34 weeks)
Increased clearance (glomerular filtration rate (GFR) 50% by 24 weeks)
Increased hepatic metabolism
Vomiting
Decreased absorption
Non compliance
Fear of prescribing by medical professionals
Therefore dose adjustment is needed in some cases
Which type of steroids are metabolised by the placenta
Non-fluoronated such as prednisolone or hydrocortisone
These are metabolised by the placenta so the foetus will get a lower dose
In contrast flurinated are not metabolised so foetal dose is equivalent to maternal dose
How can steroid use in pregnancy affect the foetus
Long term, high dose steroids may increase the risk of preterm rupture of membranes
