Pregnancy

Question 1

What types of drugs don’t cross the placenta

Answer 1

High molecular weight - insulin, heparin, enoxaparin

Question 2

Known teratogens

Answer 2

Dose dependent
-ACEi, ARBs
-AEDs
-Cytotoxics
-Gliclazide
-Sex hormones, progestogens, estrogens
-Statins
-Lithium
-Thalidomide
-Warfarin
-Valproate

Question 3

Timing of exposures
-embryonic period (up to 17 days post conception)
-1st trimester
-2nd, 3rd trimester

Answer 3

Embryonic - any cellular damage => spontaneous abortion or damaged cells replaced by normal ones

1st trimester - MOST VULNERABLE DUE TO ORGAN FORMATION

2nd, 3rd - lower risk

Question 4

Physiological changes in pregnancy affecting drug handling
-GI motility
-lung function
-skin blood circulation
-plasma volume
-body water
-plasma protein
-fat deposition
-liver activity
-glomerular filtraion

Answer 4

-GI motility => decreases
-lung function => increases
-skin blood circulation => increases
-plasma volume => increases
-body water => increases
-plasma protein => decreases
-fat deposition => increases
-liver activity => increases/decreases
-glomerular filtraion => increases

Volume of distribution changes - may affect drugs with narrow therapeutic index (digoxin, phenytoin, carbamazepine)

Question 5

Interaction between contraception and other drugs

Answer 5

Enzyme inducing drugs (carbemazepine, oxcarbazepine, rifampicin, rifabutin) may reduce plasma conc of estrogens and progestogens => reduced contraceptive action

In this case, try using an alternative method not affected by enzyme inducing drugs
-copper
-Mirena
-injectable

If PO prefered, use something with at least 50mcg of ethinylestradiol

Emergency contraception - double dose of levonorgestrel with taking with EID

Question 6

Use of painkillers
-paracetamol
-NSAIDs
-opioids

Answer 6

Paracetamol - short and occasional uses are ok
NSAIDs - avoid especially during 3rd trimester due to premature closure of ductus arteriosus
Opioids - short and occasional use of dihydrocodeine ok

Question 7

Valproate
-use in new patients, male or female

Answer 7

Must not be started in new patients U55 (male or female) unless 2 specialists independently consider and document that there is no other effective or tolerated treatment

If it’s being used in female patients
-patients/parents must be informed of the risks during pregnancy
-must sign a risk acknowledgement form annually
-must be on a highly effective contraceptive
-annual review by specialistA

Question 8

Antiepileptics in pregnancy
-what is safe, what is not

Answer 8

Lamotrigine and levetiracetam - safer in pregnancy

Carbemazepine, phenytoin, phenobarbital, topiramate - increased risk of major malformations

Phenobarbital, phenytoin - neurodevelopmental effects

Question 9

Thyroid requirements

Answer 9

Increase 30-50% in pregnancy due to
-increased renal iodide clearance
-increased TBG production
-TSH receptor stimulation by HCG
-increased thyroid hormone metabolism
-increased maternal plasma volume and maternal thyroid hormone transfer to fetus

MAINTAINING EUTHYROIDISM IS IMPORTANT IN PREVENTING MISCARRIAGE, PRETERM LABOUR AND NDD

Assess TFTs as soon as pregnancy confirmed
Ensure trimester specific ranges for TSH and T4
Regular monitoring of TFTs in first 20wks
After delivery, discuss changes and frequency of monitoring with endocrinologist
Thryoid requirements stay high during breastfeeding