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Isoniazid Pregnancy and Breastfeeding Warnings

Isoniazid is also known as: Nydrazid

Isoniazid Pregnancy Warnings

Isoniazid has been assigned to a pregnancy category C by the FDA. There are no controlled data in human pregnancies. Embryocidal effects were noted in both rats and rabbits after administration of isoniazid orally during pregnancy. While cases of suspected isoniazid induced anomalies have been reported, causality is unknown and retrospective analyses have failed to document significant teratogenic risk. Isoniazid should only be given during pregnancy when need has been clearly established. The initial therapy of active tuberculosis in pregnant patients recommended by the Centers for Disease Control includes isoniazid. Isoniazid is also recommended by the American Thoracic Society. For HIV-infected women, the USPHS/IDSA (U.S. Public Health Service/Infectious Diseases Society of America) Prevention of Opportunistic Infections Working Group recommends that chemoprophylaxis be given during pregnancy to those with a positive tuberculin skin test or a history of exposure to active tuberculosis, after active disease has been ruled out. Isoniazid is the prophylactic agent of choice unless exposure to drug-resistant tuberculosis is suspected. However, the Working Group also states that "because of theoretical concerns regarding possible teratogenicity associated with drug exposures during the first trimester, providers may choose to initiate prophylaxis after the first trimester."

Isoniazid crosses the placenta. At delivery, serum cord concentrations have been reported to range from 0% to 66% of that found in maternal serum. Reports of the use of isoniazid during pregnancy generally involve multiple drug therapy. Malformations reported which have involved isoniazid use include one case each of myelomeningocele and hypospadias. The Collaborative Perinatal Project reported 85 fetal exposures to isoniazid during the first trimester. Ten malformations were reported, which was nearly twice the normal rate. However, due to the small number of exposures, no conclusion could be drawn. Hemorrhagic complications resulting from vitamin K deficiency have been reported in two infants whose mothers received antituberculous drugs. One mother had been treated with isoniazid and rifampin, and the other with isoniazid, rifampin, and ethambutol. A third infant with hemorrhagic disease had only been exposed to ethambutol and rifampin. Pleural mesothelioma was reported in a nine-year-old child whose mother received isoniazid during the second and third trimesters of pregnancy. The carcinogenicity of isoniazid has not been documented.

Isoniazid Breastfeeding Warnings

Isoniazid and acetylisoniazid, a metabolite, are excreted into human milk. Following oral administration of 300 mg, approximately 7 mg was excreted in breast milk over 24 hours. While adverse effects in the nursing infant are not reported, it may be prudent to monitor the infant for signs of peripheral neuritis and hepatotoxicity. Isoniazid is considered compatible with breast-feeding by the American Academy of Pediatrics.

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