Lecture class for MBBS Sem IV

1. Prescribing during
Pregnancy
Dr. Pravin Prasad
M.B.B.S., MD Clinical Pharmcology
Lecturer, Lumbini Medical College
28 June, 2018 (14 Asar, 2075), Thursday

2. Questionyourself….
Is prescribing in pregnancy safe?
What makes it a special case?

3. By the end of this class, MBBS SemIV
students will be able to:
Describe the US-FDA Pregnancy category of
drugs
Explain the mechanism of teratogenicity
Appreciate the changing vulnerability of
foetus to the effect of drugs with duration of
pregnancy
List the alternative drugs that can be used
during pregnancy

4. Introduction
Drugs during pregnancy:
 Affects mother
o Therapeutic
o Non-therapeutic
 Affects the developing foetus
o Not usually desired

5. Affect of Drugs on Developing foetus
When prescribed to a pregnant lady, can
affect at three stages:
Stage of pregnancy Description Example of drugs
Fertilization and
implantation
(conception to day 17)
Failure of pregnancy
(often goes unnoticed)
Misoprostol, Ergot
alkaloids
Organogenesis (weeks
2-8 intra-uterine life)
Most vulnerable period
Severe malformations
occur
Warfarin, Alcohol,
Phenytoin
Growth and
development ( 9 week
post intra-uterine life)
Developmental and
functional
abnormalities can occur
ACE inhibitors
(hypoplasia of lungs
and kidney)
NSAIDs (premature
closure of DA)

6. US-FDACategorizationof Drugs for use in
pregnancy
Category A:
 NO RISK
 Adequate studies in pregnant women have
failed to demonstrate a risk to the foetus
 Examples:
o Inj. Magnesium sulphate
o Thyroxin

7. US-FDACategorizationof Drugs for use in
pregnancy
Category B:
 NO EVIDENCE OF RISK IN HUMANS
 Either:
o Adequate human studies are lacking, but animal
studies have failed to demonstrate a risk to the
foetus,
o Adequate studies in pregnant women have failed to
demonstrate a risk to the foetus, but animal studies
have shown an adverse effect on the foetus
 Examples:
o Penicillin V, amoxicillin, Erythromycin
o Paracetamol, Lidocaine

8. US-FDACategorizationof Drugs for use in
pregnancy
Category C:
 RISK CANNOT BE RULED OUT
 No adequate studies in pregnant women, and
animal studies are lacking or have shown
adverse effects on foetus, but potential
benefit may warrant use of the drug in
pregnant women despite potential risk
 Examples:
o Morphine, Codeine, Bupivacaine
o Atropine, Corticosteroids

9. US-FDACategorizationof Drugs for use in
pregnancy
Category D:
 BENEFIT MAY OUTWEIGHT POTENTIAL
RISK
 There is evidence of human foetal risk, but
the potential benefits from use of the drug
may be acceptable despite the potential risk
 Examples:
o Aspirin, Phenytoin, Carmazepine,
Valporate
o Lorazepam, Methotrexate

10. US-FDACategorizationof Drugs for use in
pregnancy
Category X:
 CONTRAINDICATED
 Studies in animals or humans have
demonstrated foetal abnormalities, and
potential risk clearly outweights possible
benefit
 Examples:
o Estrogen, Isotretinoin, Thalidomide

11. Affect on the developing foetus
Teratogen:
 Teratos: monstor
Teratogenicity:
 Capacity of a drug to cause foetal
abnormalities when administered to a
pregnant woman

12. Teratogenicity: Example
Thalidomide tragedy:
 Occurred in Europe
 Pregnant lady suffering
from morning sickness
received thalidomide
 Child born to them had
deformed limbs
o Phocomelia
 Drug withdrawn from

13. Teratogenicity: Examples
Foetal warfarin syndrome

14. Teratogenicity: Examples
Foetal Hydantoin
Syndrome:
• Upturned nose
• Mid facial hypoplasia
• Long upper lip with thin
vermilion border
• Cleft lip

15. Foetal Abnormality: Example

16. Prescribing in Pregnancy: What to avoid
and what to prescribe?
Drug Category/
Clinical Condition
Avoid using Safer drug
Anti-emetics Ondansetron
Domperidone
Metoclopramide
Promethazine
Peptic ulcer/GERD Cimetidine
Lansoprazole
Ranitidine,
Pantoprazole
Analgesics Aspirin, NSAIDs
Morphine
Paracetamol
Ibuprofen
Antiallergics Cetirizine
Fexofenadine
Chlorpromazine
Promethazine

17. Prescribing in Pregnancy: What to avoid
and what to prescribe?
Drug Category/
Clinical Condition
Avoid using Safer drug
Anti-helminthic Albendazole Piperazine
Niclosamide
Antihypertensives ACE inhibitors
Angiotensin
antagonists
Methyldopa
Beta blockers
Antidiabetic Sulfonylureas
Metformin
Insulin
Anticoagulants Warfarin Heparin

18. Conclusion
Drugs given to a pregnant lady may have
effects on the developing foetus
US-FDA category X drugs are
contraindicated during pregnancy
When prescribing drugs during pregnancy,
drugs labelled as “safer” should be used

19. Any questions?
Thank you!!!