Prescribing in Pregnancy Flashcards
When does the missed period usually occur, and people realise they are pregnant?
By what stage of pregnancy are most of the vital organs formed?
4 weeks
11 weeks
What are the main management principles for prescribing in pregnancy?
Consider non-drug alternatives (e.g. physiotherapy instead of painkillers, CBT instead of anti-depressants)
Only use drugs if benefit > risk
Most drugs must be prescribed off license in pregnancy - requires careful documentation
Most drugs will cross the placenta, except which type?
Which type of drugs will cross fastest?
Large molecular weight drugs
Small, lipid soluble drugs
How do each of the following aspects of pharmacokinetics change in pregnancy:
Absorption?
Distribution?
Metabolism?
Elimination?
May be affected by morning sickness
Increased plasma volume and fat stores, so the Vd increases
Decreased protein binding, increased free drug
Elimination of renally excreted drugs increases due to increased GFR
What are the main risks of prescribing in the first trimester of pregnancy?
When is the period of greatest teratogenic risk?
What is the general rule here?
Risk of early miscarriage and interruption of organogenesis
4 - 11 weeks
Avoid all drugs if possible, unless benefit > risk
There are lots of drugs that cause many defects in the 1st trimester of pregnancy, however, what do the following specifically increase risk of?
ACE inhibitors/ARBs?
Lithium?
Methotrexate?
Renal hypoplasia
CV defects
Skeletal defects
What are the main things going on in trimester two which could be disrupted by drug use?
Growth and functional development (intellect/behaviour)
Use of which drugs in the 3rd trimester may cause premature closure of the DA?
Use of which drugs in the 3rd trimester may cause respiratory depression?
Use of which drug in the 3rd trimester may cause increased bleeding at labour?
NSAIDs
Opioids
Warfarin
What are some adverse effects of taking drugs in pregnancy which can occur after delivery?
Withdrawal (opiates, SSRIs)
Sedation
Diethylstilbestrol was a drug used to prevent recurrent miscarriage. This is an example of a drug which showed a delayed effect - what was it?
Vaginal adenocarcinoma in girls aged 15-20
Potential urological malignancy in boys
In pregnancy, there is increased seizures in about 10% of women. What are some potential reasons for this?
Which anti-epileptic drugs are most important to avoid in pregnancy?
Non-compliance with medication
Changes in plasma concentration due to persistent vomiting or increased clearance
Valproate and phenytoin
Is insulin safe in pregnancy?
What is important abouts its use?
Are sulphonylureas safe in pregnancy?
Yes
Requirements will change throughout pregnancy
No - should be changed to insulin
What is it important to be aware of about BP in pregnancy?
If you need to treat hypertension in pregnancy, what are some options?
Which BP drugs should always be avoided in pregnancy?
What effect can beta blockers have on a pregnancy?
BP will drop in the second trimester
Labetalol (not in asthma), methyldopa, nifedipine
ACE inhibitors/ARBs
Can inhibit foetal growth in late pregnancy
What is the best drug to use for nausea and vomiting in pregnancy?
What is the best drug to use for a UTI in the first or second trimester?
What is the best drug to use for a UTI in the third trimester?
What is the best drug to use for pain in pregnancy?
What is the best medication to use for heartburn in pregnancy?
Cyclizine
Nitrofurantoin
Trimethorprim
Paracetamol
Antacids
Women who are deemed to be high risk of VTE in pregnancy (2 or more risk factors) should be given what drug?
When should this be taken until?
LMWH
Continue at delivery and up to 7 days postpartum
