Week 5- Prescribing in pregnancy Flashcards
NOTE
No drug is completely safe in pregnancy. So how do you know which drugs you can use. First consider non-pharmalogical methods
When would you prescribe drug therapy in a pregnant women?
When the benefits outweigh the risks.
NOTE- most drugs aren’t licensed in pregnancy- prescribe outwit license.
Which drugs aren’t likely to cross the placenta?
Large molecular weight drugs.
Which drugs cross the placenta quickly?
Small, lipid soluble drugs.
In pregnancy, what might affect the absorption of a drug?
Morning sickness may reduce absorption of a drug.
Also the increased plasma volume and fat stores means the volume of distribution increases
In pregnancy, what might affect the distribution of a drug?
Decreased protein binding means more free drug.
In pregnancy, what might affect the metabolism of drugs?
Increased liver metabolism of some drugs.
What may affect the elimination of drugs in a pregnant women?
Increased renal excretion due to increased GFR.
Does anything change in pregnant women with regards to pharmacodynamics?
No significant changes- pregnant women may become more sensitive to certain drugs.
Example- hypotension with antihypertensives in 2nd trimester.
What should you give a women with suspected pregnancy, or who is planning a pregnancy?
400mcg of folic acid 3 months prior to pregnancy and in the first three months of pregnancy.
When is the period of greatest teratogenic risk? in this period how should you handle drug therapy?
4th-11th week.
Avoid drugs if possible, unless the benefits outweigh the risk to the foetus.
what do ACE inhibitors/ARBs do in pregnancy?
They are teratogenic and cause renal hypoplasia.
What do androgens do in pregnancy?
Teratogenic- cause virilisation of the female fetus.
What do anti epileptics do in pregnancy?
Teratogenic- cardiac, facial, limb, and neural tube defects.
What do cytotoxics do in pregnancy?
Teratogenic- cause multiple defects, abortion.
What does lithium do in pregnancy?
Teratogenic- causes cardiovascular defects.
What does methotrexate do in pregnancy?
Teratogenic- causes skeletal defects.
What do retinoids do in pregnancy?
Teratogenic- cause ear, cardiovascular or skeletal defects.
What does warfarin do in pregnancy?
Teratogenic- causes limb and facial defects.
What drug can cause respiratory depression?
Opiates.
What drug can cause bleeding in labour?
Warfarin
What drugs can cause withdrawal symptoms?
Opiates
SSRI’s.
NOTE
In epilepsy- the incidence of congenital malformations is higher in untreated epilepsy than in women without epilepsy.
There are increased seizures in 10% of women.
Why are there increased seizures in 10% of women in pregnancy?
Non-compliance
Decreased plasma concentration of drug- persistent vomiting, increased clearance
