Public Health

Monitoring may curb hepatotoxicity of isoniazid TB therapy

Last Updated: 2005-07-25 13:45:01 -0400 (Reuters Health)

NEW YORK (Reuters Health) - Because hepatotoxicity associated with isoniazid therapy for tuberculosis is relatively common, particularly in older patients, monitoring of aspartase aminotransferase levels could be useful in detecting the condition, researchers report in the July issue of Chest.

Dr. Timothy Self of the University of Tennessee Health Science Center, Memphis and colleagues note that the side effects of such therapy can range from mild transient elevations in aminotranferases to rare cases of overt hepatitis.

In order to determine the overall incidence of isoniazid hepatoxicity, the researchers examined data from a public health department TB clinic obtained over a 7-year period. This covered 3377 patients aged 25 years or more.

On starting therapy, 19 had aminotranferase levels more than 5.3 times the upper limit of normal. This amounted to 5.6 per 1000 patients. Only 1 patient had prodromal symptoms associated with hepatotoxicity.

At 1 month, the number of hepatotoxic event per 1000 patients was 2.75. Corresponding numbers at 3 and 6 months of therapy were 7.20 and 4.10.

These events were more prevalent in older patients. In patients 34 year of age or less, the incidence was 4.40 per 1000. For patients aged 35 to 49 years, it was 8.54. For older patients, it was 20.83.

Age and a baseline aspartate aminotransferase level above the upper limit of normal were risk factors for hepatoxicity.

The researchers note that this and earlier reports "confirm that serious hepatic dysfunction can occur in asymptomatic patients."

Given these findings, the team concludes that limited monitoring of aminotransferase levels in all patients over the age of 35 and those with other risk factors is appropriate.

Chest 2005;128:116-123.