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DRUGS USED DURING PREGNANCY

Traditionally, medical professionals have measured pregnancy from a number of convenient points, including the

day of last menstruation, ovulation, fertilization, implantation and chemical detection. In medicine, pregnancy is

often defined as beginning when the developing embryo becomes implanted in the endometrial lining of a woman's

uterus.

Common health problems encountered during pregnancy:

1. Stress, insomnia & depression2. GI disturbances3. Pain & Fever4. Infections5. Asthma & Cough6. Allergy7. Hypertension8. Epilepsy9. Diabetes

Drugs used during pregnancy can have temporary or permanent effects on the fetus.

1991 WHO International Survey of Drug Utilization in Pregnancy:

86% of women took medication during pregnancy. Despite this high rate of medication intake, most drugs are not labeled for use during pregnancy.

Adverse effects drugs used during pregnancy:

Spontaneous abortion Fetal growth retardation Teratogenicity (permanent anatomical/physiological abnormality) Direct drug toxicity Neonatal drug withdrawal Long term effects on neurobehavioral development Carcinogenesis

Factors to be considered while prescribing drugs during pregnancy:

Minimize use of medications and for shortest duration possible

Timing of exposure (sensitive period)All-or-none period

*Organogenesis* (Avoid drug administration, if at all possible during 1st trimester)

Brain development (fifth week of pregnancy)

Dose of drug (threshold, dose-response) Genetic susceptibility Role of underlying maternal disease Other exposures such as alcohol and cigarette smoking

Thefirst12 weeks (upto 3 months) of pregnancy are considered to make up thefirst trimester.

Weeks 13 to 28 (upto 7 months) of the pregnancy are calledthe second trimester.

Weeks28 onwards of the pregnancy are calledthe third trimester.

Influence of physiological changes in pregnancy on drug dose requirements:

prolonged gut transit time plasma albumin concentration amounts of body water and fat renal blood flow in 3rd trimester liver blood flow does not change enzymatic activity changes

CYP 3A4, 2D6, 2C9 (by progesterone)

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CYP 1A2, 2C19

hyperventilation placenta

Factors that affect placental drug transfer & drug effects on fetus:

1. Physicochemical properties of the drug

a. lipid solubility

b. degree of drug ionization

c. molecular sized. degree of protein binding

2. Dose & duration of exposure to the drug

3. Stage of placental & fetal development at time of exposure to the drug

4. Genetic predisposition & susceptibility

The pregnancy category of a pharmaceutical agent is an assessment of the risk of fetal injury due to the

pharmaceutical, if it is used as directed by the mother during pregnancy. It does not include any risks conferred by

pharmaceutical agents or their metabolites that are present in breast milk.

In 1979, the United StatesFood and Drug Administration (FDA) introduced a classification of fetal risks due to

pharmaceuticals. This was based on a similar system that was introduced in Sweden one year earlier.

The United States FDA has the following definitions for the pregnancy categories:

United States FDA Pharmaceutical Pregnancy Categories

Pregnancy

Category A

Adequate and well-controlled human studies have failed to demonstrate a risk to the fetus in the first

trimester of pregnancy (and there is no evidence of risk in later trimesters).

Pregnancy

Category B

Animal reproduction studies have failed to demonstrate a risk to the fetus and there are no adequate

and well-controlled studies in pregnant women OR Animal studies have shown an adverse effect,

but adequate and well-controlled studies in pregnant women have failed to demonstrate a risk to the

fetus in any trimester.

Pregnancy

Category C

Animal reproduction studies have shown an adverse effect on the fetus and there are no adequate

and well-controlled studies in humans, but potential benefits may warrant use of the drug in

pregnant women despite potential risks.

Pregnancy

Category D

There is positive evidence of human fetal risk based on adverse reaction data from investigational or

marketing experience or studies in humans, but potential benefits may warrant use of the drug in

pregnant women despite potential risks.

Pregnancy

Category X

Studies in animals or humans have demonstrated fetal abnormalities and/or there is positive

evidence of human fetal risk based on adverse reaction data from investigational or marketing

experience, and the risks involved in use of the drug in pregnant women clearly outweigh potential

benefits.

Pregnancy

Category NFDA has not classified this drug.

One characteristic of the FDA definitions of the pregnancy categories is that the FDA requires a relatively large

amount of high-quality data on a pharmaceutical for it to be defined as Pregnancy Category A. As a result of this,

many drugs that would be considered Pregnancy Category A in other countries are allocated to Category C by the

FDA.

Classification of a few important drugs/vaccines

Antibacterial agents

Category B : Penicillin, metronidazole, nitrofurantoin, cephalosporins, clindamycin, terbinafine, somemacrolides e.g. azithromycin, erythromycin

Category C : Some aminoglycosides, chloroquine, quinolones, mebendazole, fluconazole Category D : Tetracyclines, gentamicin, tobramycin

Cardiovascular drugs

Category B : Heparin (LMW)

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Category C : Heparin (conventional), beta-blockers, (dihydropyridine) calcium antagonists, furosemide,digoxin, methyldopa

Category D : ACE inhibitors, ARBs, coumarins, thiazides, diltiazemCentral nervous system drugs

Category B : Acetaminophen, caffeine Category C : Aspirin, clonidine, rofecoxib Category D : Carbamezapine, valproic acid, diazepam, lithium vac

Others

Category C : Vaccines such as Tetanus toxoid, polio vaccine , BCG vaccine, hepatitis A vaccine, hepatitisB vaccine and rabies vaccine.

Category D : Alcohol is one of the most dangerous drugs for a pregnant women ,especially in the earlyweeks of pregnancy.

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