If isoniazid chemoprophylaxis reduces the incidence of clinical disease by only 54%-88% (76), then 11 to 18 persons must be given isoniazid to prevent one future case of active tuberculosis.
In 1992, Snider and Caras reviewed the most serious hazard of isoniazid chemoprophylaxis, death from isoniazid-associated hepatitis (62):
Despite the limitations of this survey, we believe the following tentative conclusions are warranted: (1) As suggested by Dash and colleagues, deaths due to INH-associated hepatitis are probably less frequent now than in the early 1970s, but they are still occurring. Efforts to carefully select and monitor patients on INH preventive therapy [prophylaxis] must be continued; (2) Women may be at increased risk of death from INH-associated hepatitis. Therefore, women taking INH should be carefully monitored for hepatotoxicity and preventive therapy recommendations for women should be reconsidered; (3) As suggested by Franks and colleagues, the postpartum period may represent a period when women are especially vulnerable to INH hepatotoxicity; it may be prudent to avoid INH during the postpartum period or at least to monitor postpartum women more carefully; (4) Additional research is needed to identify groups at risk of death from INH-associated hepatitis, to quantify this risk in relative and/or absolute terms, and to identify cofactors that may influence the risk; (5) Better surveillance for INH-associated hepatitis death is warranted.
NIOSH concludes that any use of isoniazid chemoprophylaxis as a substitute for implementing all administrative, engineering, and personal respiratory protection controls indicated for protecting workers in a health-care facility from infection with tuberculosis transmitted in the facility is inconsistent with the rights of workers and obligations of employers established by the Occupational Safety and Health Act of 1970.
B. Potential Respirator Leakage—NIOSH evaluated the levels of overall efficacy and reliability of personal respiratory protection offered by different types of NIOSH - certified respirators that might be suitable for personal respiratory protection against aerosolized droplet nuclei (57,77,78,79,80). This evaluation focused on two drawbacks that characterize all air-purifying masks equipped with particulate filters-face-seal leakage and filter leakage.
