Sunday, April 26, 2009



The role of medical pharmacology, which is often defined as science of substances used to prevent, diagnose, and treat disease. Toxicology is the branch of pharmacology which deals with the undesirable effects of chemicals on living systems, from individual cells to complex ecosystems.

Drug therapy in pregnancy, most of drugs transfer from the maternal to the fetal circulation may be influenced by maternal, placental and fetal factors. Many therapeutics drugs given during pregnancy, therefore, are “potentially” teratogenic or fetotoxic.
Defining a teratogen: To be considered teratogenic, a candidate substance or process should:
1. Result in a characteristic set of malformations, indicating selectivity for certain target organs.
2. Exert its effects at a particular stage of fetal development, during a limited time period of organogenesis of the target organs;
3. Show a dose dependent incidence. Some drugs with known teratogenic or other adverse effects in pregnancy are listed.

The widely cited Food and Drug Administration system for teratogenic potential is an attempt to quantify teratogenic risk from A [safe] to X [definite human teratogenic risk]. The teratogenic drug actions, for example, Thalidomide is an example of a drug that may profoundly affect the development of the limbs after only brief exposure. This exposure, however, must be at a critical time in the dependent of the limbs. The thalidomide risk occurs during the fourth through the seventh weeks of gestation because it is during this time that arms and legs develop.
The fetotoxic drugs are a general name of undiserable effects on fetus during pregnancy.

Counceling women about teratogenic risk:
Since thalidomide disaster, medicine has been practiced as if every drug were a potential human teratogen when, in fact, fewer than 30 such drugs have been identified, with hundreds of agents proved safe for the unborn. Owing to high levels of anxiety among pregnant women, every year many thousands of women need counseling about fetal exposure to drugs, chemical and radiation. Clinicians who wish to provide such counsel to pregnant women must ensure that their information is up to date evidence-based and that the woman understands that the baseline teratogenic risk in pregnancy [the risk of a neonatal abnormality in the absence of any known teratogenic exposure] is about 3 %.

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