2. DRUGS IN PREGNANCY
DR. NAHEED BANO
Assistant Professor, Obs/Gynae
Rawalpindi Medical College, Rawalpindi.
3.
4. IMPORTANT ASPECTS
1. Physiological changes of pregnancy
affect DRUG METABOLISM
2. Drug may cross the placenta and affect
the fetus (TERATOCENICITY)
5. PHYSIOLOGICAL CHANGES OF
PREGNANCY THAT AFFECT DRUG
METABOLISM
GIT:
Nausea
and
vomiting
of
early
pregnancy
Acid content of the stomach is ↓
Delayed gastric emptying
Continued:
6. SKIN AND MUCOUS MEMBRANE:
↑ Blood flow to the skin leads to more rapid
absorption e.g. glyceryl trinitrate
patches
used to suppress preterm labour
→ Blood flow to nasal and oral mucous
membrane
absorption.
→
leads
to
more
rapid
7. CNS:
↑ Vascularity of epidural space e.g. opiates used
for analgesia are rapidly absorbed
PLASMA AND BLOOD VOLUME:
↑ Plasma and blood volume causes
haemodilution affecting drug concentration
PLASMA PROTEINS:
↓ In plasma proteins affect drugs that are
bound to proteins e.g. diazepam, phenytoin
leading to ↑ free drug in circulation
URINARY SYSTEM:
↑ Renal blood flow and GFR affecting
concentration and elimination of many drugs.
8. TERATOGENICITY
Drugs that affect organogenesis are described
as TERATOGENIC DRUGS
Drug exposure accounts for 2-3 % of all birth
defects
Most critical period is embrogenic period
which is from 2nd to 8th week post conception or
day 31 to day 71 from LMP in a 28 day cycle
Exposure prior to day 31 produces all or none
effect i.e. either the fetus dies in utero or has
no effect.
Exposure from day 31 to day 71 may lead to
fetal abnormality or fetal death.
14. FDA CLASSIFICATION OF DRUG
SAFETY IN PREGNANCY
United
States
food
and
drug
administration categories for drug use
in pregnancy
A. Controlled studies show no risk
B. No evidence of risk in humans
C. Risk cannot be ruled out
D. Positive evidence of risk
E. Contra – indicated in pregnancy