Pharmacology in Pregnancy

Question 1

Factors influencing drug bioavailability in pregnancy?

Answer 1

• Increased circulating volume
• Increased renal blood flow (hence increased renal clearance of water-soluble drugs)
• Increased 3rd space
• Increased fat content
• Decreased albumin and binding proteins (hence free drug levels may not be low)
• Increased gastric emptying time
• Increased liver metabolism (hence increased clearance of drugs dependent on liver metabolism).
• Liver blood flow shows no change in pregnancy (hence no change in clearance of drugs whose elimination is dependent on liver blood flow, e.g. propranolol)

Question 2

Which drugs are potential teratogens?

Answer 2

All the ‘A drugs’
- Anticonvulsants
- Antibiotics
- Anticoagulants
- Antimetabolites
- Androgens
- Alcohol
- Antipsychotics

Question 3

Teratogenic effects of exposure < 20days

Answer 3

Limb defects

Question 4

Teratogenic effects of exposure day 20

Answer 4

Anencephaly

Question 5

Teratogenic effects of exposure 34 days

Answer 5

Transposition of great vessels

Question 6

Teratogenic effects of exposure 36 days

Answer 6

Cleft lip

Question 7

Teratogenic effects of exposure 42 days

Answer 7

VSD
Syndactyly

Question 8

Teratogenic effects of exposure 84 days

Answer 8

Hypospadias

Question 9

Most drugs cross the placenta except HIT. What is HIT?

Answer 9

Heprin
Insulin
Tubocurarine

Question 10

Drugs that cause abortion (MET)

Answer 10

Misoprostol
Ergotamine
Thrombolytics

Question 11

FDA pregnancy category

Answer 11

A - No fetal risk in pregnancy
B - Animal studies have failed to demonstrate a risk to fetus. No adequate studies in pregnant women
C - Animal studies have shown adverse effect on the foetus. No adequate studies in pregnant women. Benefit of drug outweighs the potential risk
D - Evidence of risk of human teratogenicity. Potential benefits outweigh potential risk.
X - Evidence of risk of human teratogenicity. Potential risks outweigh potential benefit of drug.