isoniazid, Nydrazid (discontinued), Laniazid (discontinued), INH (discontinued) (cont.)

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PREGNANCY: Isoniazid has not been shown to cause birth defects in humans or animals; however, studies in rats and rabbits have shown that it may increase the risk of fetal death. Nevertheless, tuberculosis is a very serious infection, and many women have been treated with isoniazid during pregnancy with no problems in their infants. Ultimately, the physician and the pregnant patient must evaluate the risks and benefits of isoniazid.

NURSING MOTHERS: Isoniazid is secreted into breast milk, however, it has not been reported to cause problems in nursing babies. Ultimately, the physician and the nursing mother must evaluate the risks and benefits of Isoniazid.

SIDE EFFECTS: When Isoniazid is broken down by the liver, one of the products is acetylhydrazine, a potent toxin for the liver. When taken over a long period of time at standard doses, Isoniazid can cause important and even fatal liver injury (hepatitis) in approximately 1 out of every 100 patients. Isoniazid-associated hepatitis usually occurs during the first three months of treatment but can occur at any time during therapy or even many months after starting treatment. Elevated blood liver tests occur in between 1 in 20 and 1 in 10 patients. Usually, enzyme levels return to normal despite continuation of the isoniazid, but in some cases progressive liver damage and even death occurs.

The risk of developing hepatitis is age-related. It occurs in less than 1 per 1,000 patients under 20 years of age, 3 per 1,000 patients 20-34 years of age, 12 per 1,000 patients 35-49 years of age, 23 per 1,000 patients 50-64 years of age, and 8 per 1,000 patients over 65 years of age. The risk of hepatitis is increased by daily consumption of alcohol. Among individuals who complete a full course of prophylaxis (prevention of tuberculosis), the hepatitis-related death rate (mortality) is 23-58 patients per 100,000 patients, far lower than the frequency of hepatitis. The mortality rate among individuals who develop symptoms of Isoniazid-induced hepatitis (not just minor abnormalities of liver tests) is approximately 10%. In one U. S. Public Health Service Surveillance Study involving 13,838 persons taking Isoniazid, there were 8 deaths among 174 cases of hepatitis, a mortality rate of 5%. There seems to be an increased risk of fatal hepatitis among women, particularly African-American and Hispanic women. The risk also may be increased during postpartum or immediately after pregnancy. Because of the risk of hepatitis, patients taking isoniazid should have their blood liver tests monitored monthly and should notify their physicians immediately if symptoms or signs of hepatitis arise. These symptoms and signs include unexplained loss of appetite, nausea, vomiting, dark urine, yellow skin or a yellowish tinge to the whites of the eyes, persistent fatigue, weakness or fever of greater than 3 days duration, or abdominal tenderness or discomfort, especially in the right upper part of the abdomen.



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