This document discusses drugs in pregnancy, including their effects on the fetus and considerations for prescribing. It covers several key points: 1. Almost all drugs cross the placenta and can harm the embryo/fetus, so the risk-benefit ratio must be considered when prescribing to pregnant women. 2. Teratogens are drugs that can cause birth defects, and examples like thalidomide and valproate are discussed. The timing of exposure is important, as the first trimester is the period of organogenesis. 3. The FDA categorizes drugs into risk categories from A to X based on human and animal data. Category X drugs are considered too dangerous and contraindicated in pregnancy.

1. Drugs in Pregnancy
Sanjaya Mani Dixit
Assistant Prof of Pharmacology

2. Contents
lIntroduction
lTeratogens
lDrugs in pregnancy
lEffect of Drugs on Pregnancy
lEffect of Pregnancy on Drugs
lFDA Risk Category
lDrug Transfer to the Fetus
lPharmacology in fetus
lDrug Transfer Pregnancy Vs Lactation
lPrinciples of prescribing in pregnancy
lDrugs Safe for prescribing in Pregnancy

5. Introduction
lPlacenta is not a protective barrier-- Almost all the drugs
given to the mothers cross the placenta to some extent, and
therefore fetal exposure will occur.
lDrugs can harm the embryo or fetus at any time during
pregnancy (Embryotoxicity, Teratogenicity, Fetotoxicity).
lTherefore, the risk benefit ratio must be considered.
lThe risk to the fetus should always be considered while
prescribing to a women of child bearing age.

6. Teratogens
lA teratogen is a drug or other substance capable
of interfering with the development of an embryo/
fetus that may lead to birth defects or
developmental malformations.
lGross structural abnormalities
lFunctional deficiencies
lIntrauterine growth restriction
lBehavioral aberrations
lDemise

7. Teratogenic drugs
lThalidomide-- Phocomelia
lMethotrexate-- Abortifacient
lAnticoagulants– Growth retardation
lAndrogen– Masculization of female fetus
lTetracycline -- Impair bone development
lDiethylstilbestrol– Vaginal Adenocarcinoma
lVitamin A derivatives- Major organ malformations
Not all the damaging effects of intrauterine exposure to drugs are
obvious at birth, some may only manifest later in life.
Adenocarcinoma of the vagina
after puberty

8. Teratology
• Evaluation of Potential Teratogens
1. The Defect must be completely characterized
2. The Agent must cross the placental barrier
3. Exposure Must occur during the critical developmental period
4. There must be a biologically plausible association
5. Epidemiological findings must be consistent
6. Suspected teratogen causes a defect in an animal
• Pre-implantation period: All or none period
• Embryonic period: Structural malformations
• Fetal period: Functional vulnerabilities

10. Teratogenic Factors
lTiming of exposure
lDevelopmental stage during exposure
lMaternal dose and duration
lMaternal pharmacokinetics
lGenetic factors/phenotypes
lInteractions between agents

11. Drugs needing Precautions
lAzathioprine, methotrexate: avoid pregnancy [ for 1-2 years]
lTestosterone: Masculization of female fetus
lWarfarin: Fetal warfarin syndrome (nasal defects- 1st trimester; 2nd
trimester CNS malformations)
lAlcohol [> 40 gm/day]: Fetal alcohol syndrome
(Abnormalities in growth and in cardiac, skeletal, muscular,
genitourinary, CNS development)
Majority of implicated drugs are low grade teratogens, i.e.
increase the incidence of malformations only slightly, which
may be very difficult to detect, confirm or refute.

12. Sensitivity to Teratogen during Development

13. Root cause of problem
1.Inappropriate use of drugs
2.Over the counter drugs
3.Poly-pharmacy
Outcomes in Pregnancy:
lThalidomide disorder [1960- 1962]: phocomelia
[41 cases of 46 mothers]
lSodium valproate: spina bifida
lPhenytoin : Fetal hydantoin syndrome
lDiethylstilbestrol: vaginal adenocarcinoma

14. Phenytoin Teratogenicity

15. Drugs in pregnancy
There are two major considerations regarding drugs in
pregnancy:
A.The effects of drugs on pregnancy
A.The effects of pregnancy on drugs

16. A. Effects of drugs on pregnancy
lIt is important to note that approximately 3-5% of all live
births have fetal abnormality.
lDrugs are responsible for only 0.03-0.25% of all
malformations; smoking and alcohol being the major cause
for it.
lThe exposure of the fetus during 18- 55 days of life results
in malformations of organs, while after 55 days any
adverse effect of the drug may be shown in growth or
function of the fetal organs.

17. Gestational periods
Pre-implantation [18 days]: embryo toxicity (Blastogenesis)
First trimester [18-56 days]: congenital malformations (period of
organogenesis- Most critical period)
2nd / 3rd trimester: Affect growth and functional development
[mental retardation, postnatal carcinoma]
Labor [full term]: Adverse effects on labor or neonate after the
delivery

18. B. Effects of pregnancy on drugs
Volume of Distribution
Vd may be increased by about 20% for both lipid
soluble and water soluble drugs. This may cause loading dose
to be increased.
Protein Binding
Maternal albumin and AAG percentage decrease
throughout the pregnancy to a low at the time of delivery. This
may be attributed to the increase in Vd, leading to a volumetric
dilution of proteins, not altering the overall amount of the protein.
So, it is considered not to affect the drug action.

19. B. Effects of pregnancy on drugs
Clearance
lDuring pregnancy the clearance rate of drugs is
increased since the liver metabolism and renal
elimination both are increased.
lThe cardiac output is increased up to 30% during
pregnancy, increasing the renal blood flow and GFR. Also
there is enzymatic induction due to hormonal
imbalances (progesterone increased).
lSo the maintenance doses of drugs often need to be
increased during pregnancy.

20. Implications
A. Increase the dose of: (Increased Vd)
lAmpicillin [double]
lCefuroxime, lithium, phenytoin
B. As usual dose:
- BDZ, furosemide, propranolol, aspirin, metronidazole

21. FDA Risk Category
lA,B,C,D & X
lA: safe
lX: contraindicated
Teratogenicity
“Any birth defect induced at any stage of pregnancy &
detected at birth or later life, caused by exogenous agents”.

23. FDA Risk Category
lA Controlled studies in animals and human have not
shown risk (Mg Sulphate, Thyroxine)
lB Animal studies have shown risk but controlled studies in
human have not. (B-lactams, methyldopa, Paracetamol)
lC Animal studies have shown risks but studies in human
have not been done. (Antipsychotics, laxatives, antihistamines)
lD Positive incidence of some risks exists but benefits may
out-weight in some cases. (Anticonvulsants, Ethanol, Warfarin,
TTC)
lX Too dangerous— Contraindicated. (Thalidomide, Vit A
derivatives, some cytotoxics)

24. FDA Risk Category
lMajor problems exist
lEstablished in 1979
lLack of data in humans
lWhat does a “C” drug really mean
lDifficult to assign an “A” to any drug
lDoes not address lactation safety

25. Clinical problems
A male baby of epileptic mother, was born with bulged lump on
back at L1- L3.
A.What is your diagnosis?
B.Name the drug which is responsible for this defect.
C.How will you correct this fetal defect?

26. Clinical problems
lDiagnosis—Spina Bifida
lDrug- Sodium valproate
lCorrection
lSurgery

27. Drug Transfer to the Fetus
lPlacental transfer may occur by:
lPassive diffusion
lFacilitated diffusion
lActive transport
lPlacental surface area
lPlacental metabolism

28. Factors affecting placental drug
transfer
•Molecular weight < 500 Daltons
•pH
•Lipid solubility
•Drug Absorption
•Drug Distribution
•Plasma Protein binding
•Physical characteristics of the placenta
•The Pharmacological activities of the drug
•Co-existence of disease states
•Rate of maternal and placental blood flow

29. Pharmacology in fetus
Placental transfer of drug:
lAs pregnancy advances the increase in the size of
placenta occurs which in-turn increases the
transfer of drugs
lPlacenta may metabolize the drugs & protect the
fetus [prednisolone- prednisone, hydrocortisone-
cortisone] So, better preferred than
Dexamethasone and Beclomethasone.

30. A. Drug Metabolism:
1. Well developed oxidation [dealkylation], glycine & sulfate conjugation
2. Decreased -- Hydroxylation, reduction, hydrolysis & glucuronidation
[raised t1/2 of phenytoin, phenobarbitone, tolbutamide,
aspirin & chloramphenicol]
B. Excretion:
Slower excretion of drugs [low RBF & GFR [30% of
adult] & more acidity of urine
lAminoglycosides, digoxin, penicillin, indomethacin, sulfonamide,
pethidine
Pharmacology in fetus

31. Effect of drugs in fetus &
new borne
lAt plasma concentration, the response of fetal tissues to most
drugs is ~ to or < maternal tissues
lExcept: drugs used during 2nd or 3rd trimester may be raised
response or response peculiar to fetus
lTetracycline deposition in bone & teeth (after 18th week)
lHemorrhage due to warfarin, etc.
lGoiter due to anti-thyroid drugs
lRespiratory depression due to opiates, barbiturates

32. Drug Transfer Pregnancy Vs Lactation
lAcross Placenta
lSize < 500
daltons
lHigh blood
concentration
lInto Breast Milk
lSize < 200
daltons
lDrug pKa
lEquilibration
speed
lHigh blood
concentration

33. General Advice
•Avoid all drugs if possible, including smoking, alcohol, and
caffeine.
•Avoid all drugs in the first trimester.
•Choose drugs of proven efficacy or least toxicity.
•Use short courses and the smallest doses.
•Drugs should be prescribed in pregnancy only if the expected
benefit to the mother is thought to be greater than the risk to the
fetus.
Absence of information on risk does not imply safety.

35. Safe drugs in Pregnancy
lCyclizine, metaclopramide [with caution]
lNon systemic antacids
lPenicillin, cephalosporin
lINH, ethambutol
lPiperazine
lDigoxin
lHeparin, paracetamol, phenobarbitone

40. Multiple Choice Questions
All of the following drugs are teratogenic, Except
A.methotrexate
B.tetracycline
C.heparin
D.phenytoin

41. Multiple Choice Questions
All of the following drugs are teratogenic, Except;
A.methotrexate- “X”-Abortifacient
B.tetracycline --Impair bone development
C.heparin
D.Phenytoin-- Fetal hydantoin syndrome (FHS)

43. Do you think teratogenicity is
linked only with pregnant
women?
Think again….
Paternal Teratogenic exposure
can lead to loss of pregnancy too.

47. www.medipuzzle.com

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ENJOY
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