Isoniazid toxicity in health care workers

Treatment of tuberculosis infection in children

INTRODUCTION

Identifying and treating children with tuberculosis (TB) infection in both low and high-TB burden settings will decrease the incidence of TB disease worldwide. Areas covered: This review covers each of the available TB infection treatment options for children based on effectiveness, safety, tolerability and treatment completion rates. Six to 9 months of daily administered isoniazid is no longer the treatment of choice for many children with TB infection. Shorter, rifamycin based, TB infection treatment regimens are effective, safe and easier for children to complete. Fluroquinolone-based regimens are recommended for the treatment of children infected by a source case with drug-resistant TB. Directly observed therapy (DOT) programs improve childhood TB infection treatment completion rates. Expert commentary: As shorter, rifamycin-based, TB infection treatment regimens offer superior treatment success rate in both adults and children; the widespread use of these regimens has huge potential to decrease the burden of TB disease worldwide. The implementation of these programs will involve improving patient access to the medications, decreasing their cost to the patient, and the use of novel electronic methods to document patient treatment completion.

Treatment of Latent Tuberculosis Infection in Children

Treatment of latent tuberculosis infection (LTBI) is an effective way of preventing future cases of tuberculosis disease. We review pediatric and adult studies of LTBI treatment (isoniazid and rifampin monotherapy, isoniazid plus rifampin, isoniazid plus rifapentine, and rifampin plus pyrazinamide). Based upon this review and our pediatric experience, we can offer recommendations for routine (isoniazid) and alternative courses of therapy.

The use of anti-tuberculosis therapy for latent TB infection

Tuberculosis infection is of global public health significance, with millions of incident cases each year. Many cases, particularly in low-prevalence settings, result from the reactivation of latent tuberculosis infection (LTBI); potentially acquired years prior to active disease. Up to one-third of the world’s population has been infected with LTBI, and so may be at risk for future active TB disease. A variety of antituberculosis medications and treatment regimens have now been evaluated in the management of LTBI, with the aim of eradicating tuberculosis bacilli and reducing the likelihood of subsequent reactivation disease. This article reviews LTBI therapies and their use in clinical contexts, and considers future directions for individual and population-based strategies in LTBI management.

Isoniazid-associated hepatitis and antiretroviral drugs during tuberculosis prophylaxis in hiv-infected adults in Botswana

RATIONALE

Little is known about the incidence of isoniazid-associated hepatitis in HIV-infected Africans who receive both isoniazid preventive therapy (IPT) and antiretroviral therapy (ART).

OBJECTIVES

To assess the rate of and risk factors for isoniazid (INH)-associated hepatitis in persons living with HIV (PLWH) during IPT.

METHODS

PLWH recruited for a clinical trial received 6 months of open-label, daily, self-administered INH at public health clinics. At screening PLWH were excluded if they had any cough, weight loss, night sweats, or other illness. Alcohol abuse was defined as meeting any CAGE criterion. INH-associated hepatitis (INH-hepatitis) was defined as having either alanine or aspartate aminotransferase greater than 5.0 times the upper limit of normal regardless of symptoms when INH was not excluded as the cause.

MEASUREMENTS AND MAIN RESULTS

Of 1,995 PLWH enrolled between 2004 and 2006, 1,762 adhered to at least 4 months of IPT and were analyzed. Nineteen (1.1%) developed hepatitis probably or possibly associated with INH including one death at month 6; 14 of 19 (74%) occurred in months 1-3. Antiretroviral therapy (ART) was received by 480 participants but was not statistically associated with INH-hepatitis (relative risk [RR], 1.56; 95% confidence intervals [CI], 0.62-3.9); those receiving nevirapine had a higher rate (2.0%) than those receiving efavirenz (0.9%; P = 0.34). Although alcohol use did not reach significance (RR, 1.42; 95% CI, 0.57-3.51), meeting at least one CAGE criterion approached statistical significance (RR, 2.37; 95% CI, 0.96-5.84). Neither age greater than 35 years nor the presence of hepatitis B virus core antibody was associated with INH-hepatitis.

CONCLUSIONS

The observed rates of INH-hepatitis were similar to published data. Six months of IPT, which is recommended by the World Health Organization, was relatively safe in this, the largest cohort of African PLWH. Clinical trial registered with www.clinicaltrials.gov (NCT 00164281).

Treatment of Latent Tuberculosis Infection: Challenges and Prospects

This article reviews the treatment of latent tuberculosis infection in HIV-seropositive and HIV-seronegative persons.

[Primary prevention and treatment of latent tuberculosis infection with isoniazid: efficacy of a control program, 1997-2002]

OBJECTIVE

To analyze the efficacy of a specific program for the study and follow up of tuberculosis contacts. To study factors related to low adherence to treatment and to the development of liver toxicity caused by isoniazid.

PATIENTS AND METHODS

Between December 1996 and December 2002, we found 458 contacts of 79 cases of pulmonary tuberculosis in patients uninfected by human immunodeficiency virus. The contacts were screened for tuberculosis infection and chemoprophylaxis was prescribed according to the recommendations of the Spanish Society of Pulmonology and Thoracic Surgery (SEPAR).

RESULTS

We identified 3 cases of tuberculosis among the contacts (prevalence 0.8%). Chemoprophylaxis with isoniazid was prescribed for 215 contacts. One hundred sixty-nine (79%) completed the prophylaxis protocol. The rate of adherence to treatment was lower in immigrants than in nonimmigrants (odds ratio, 3.42; 95% confidence interval, 1.03-11.04; P=.02). Forty-three patients (22%) developed liver toxicity during treatment, which had to be suspended in 3 cases. Duration of chemoprophylaxis was the only independent variable associated with liver toxicity (odds ratio, 3.80; 95% confidence interval, 1.10-13.13; P=.03).

CONCLUSIONS

Our study demonstrates the effectiveness of a specific program of study and follow up of tuberculosis contacts. Immigrants require tailored strategies to improve their adherence to the program. The duration of chemo-prophylaxis plays an important role in the development of liver toxicity.

Managing antituberculosis drug therapy by therapeutic drug monitoring of rifampicin and isoniazid

BACKGROUND

Current therapeutic regimens with rifampicin and isoniazid have proven successful in treating tuberculosis, however, toxicity, therapeutic failure, relapse and multiple drug resistance are serious concerns. Optimizing drug dose using therapeutic drug monitoring (TDM) may be a better approach than administering therapy as a standard dose.

AIMS

To establish and evaluate a TDM service to optimize rifampicin and isoniazid therapy.

METHODS

A TDM service for rifampicin and isoniazid was established in November 1998. Drug concentration data were collected, with relevant information to interpret the results. The reason for the request, information on concomitant drug administration and a questionnaire to assess clinical response to the drug results were also obtained.

RESULTS

Ninety patient episodes were accepted for study. The rifampicin plasma concentrations showed significant scatter, with 46% of the rifampicin concentrations below the normal range and 2% above the normal range. Similarly, 48% of isoniazid concentrations were below the lower target of the normal range and 29% were above the upper normal limit. There was a greater proportion of isoniazid concentrations above the normal range in female patients.

CONCLUSION

Significant pharmacokinetic variability was observed for rifampicin and isoniazid in the patient population studied. Further, a substantial number of plasma concentrations fell outside the suggested normal range for both drugs. Isoniazid plasma concentrations were significantly higher in female patients compared with male patients. Despite these abnormal results, the dose of rifampicin and isoniazid was altered in only 17% of patients, however, many patients received follow-up education because of the drug result. The service was considered valuable by 83% of respondents to the questionnaire. While TDM of rifampicin and isoniazid is a valuable tool to optimize the dose of these drugs in some patients, there is an urgent need for concentration-effect studies and possibly education on the principles and practice of TDM for these drugs.

Dual skin testing for latent tuberculosis infection: a decision analysis

BACKGROUND

Recent data indicate that 10- to 14-mm Mycobacterium tuberculosis purified protein derivative (PPD) reactions are often due to prior infections with nontuberculous mycobacteria. Therefore, use of a 10-mm cutpoint to define latent tuberculosis infection (LTBI) results in false-positive diagnoses and unnecessary treatment for LTBI. A second skin test, Mycobacterium avium sensitin (MAS), has been shown to accurately identify false-positive PPD results.

OBJECTIVE

To compare the costs and accuracy of a single skin-test strategy (SST) with PPD alone with a dual skin-test strategy (DST) where 10- to 14-mm PPD results are also tested with MAS.

METHODS

A decision analytic model was developed to evaluate the two strategies. The model accounted for the costs of skin testing, the costs of LTBI treatment, the costs of undetected LTBI, and the sensitivity and specificity of each strategy.

RESULTS

We estimated that DST saved US dollars 3 per subject tested compared to SST. Savings were due to a reduction in false-positive PPD results and consequent reduction in unnecessary treatment for LTBI of >60%. The DST strategy was associated with a minimal increase in undetected LTBI (6% vs 7%). Results were stable for a broad range of parameter values.

CONCLUSIONS

DST is a promising approach to improving the specificity of LTBI testing when a 10-mm PPD cutpoint is used and would reduce costs and unnecessary drug treatment.

Isoniazid preventive therapy, hepatitis C virus infection, and hepatotoxicity among injection drug users infected with Mycobacterium tuberculosis

Treatment of latent Mycobacterium tuberculosis infection with isoniazid can cause hepatotoxicity, but the risk of isoniazid-associated hepatotoxicity among persons coinfected with hepatitis C virus (HCV) is unknown. We conducted a prospective study among 146 injection drug users with M. tuberculosis infection and normal baseline hepatic transaminase values who were treated with isoniazid. Of 146 participants, 138 (95%) were HCV-seropositive. Thirty-seven participants (25%) were human immunodeficiency virus (HIV)-seropositive. Thirty-two (22%; 95% confidence interval [CI], 16%-30%) of 146 participants developed transaminase value elevations to >3 times the upper limit of normal. Transaminase value elevation was associated with concurrent alcohol use but not with race, age, presence of hepatitis B surface antigen, HIV-1 infection, or current injection drug use. Isoniazid was withdrawn from 11 participants (8%; 95% CI, 4%-13%). Of 8 deaths during follow-up, none were attributed to isoniazid-associated hepatotoxicity. The risk of transaminase value elevation and drug discontinuation for HCV-infected persons receiving isoniazid was within the range reported for populations with lower HCV prevalence.

Assessing the risk of tuberculosis infection among healthcare workers: the Melbourne Mantoux Study. Melbourne Mantoux Study Group

OBJECTIVE

To determine the potential prevalence of nosocomial infection with Mycobacterium tuberculosis among hospital employees in teaching hospitals in Melbourne.

DESIGN

Cross-sectional survey of positive tuberculin skin test (Mantoux) responses among employees in 14 public hospitals in Melbourne, January 1996 to April 1999.

PARTICIPANTS

All consenting employees in participating hospitals (4,070 healthcare and 4,298 non-healthcare workers; participation rates, 13%-66%).

OUTCOME MEASURES

Prevalence of positive responses to tuberculin skin tests among healthcare and non-healthcare workers and association with employee and hospital characteristics.

RESULTS

Healthcare workers were significantly more likely to have a positive tuberculin response than non-healthcare workers (19.3% versus 13.7%; odds ratio, 1.5; 95% CI, 1.3-1.7; P<0.001). Multivariable analysis revealed that age, country of birth (high versus low tuberculosis [TB] prevalence), history of BCG (bacille Calmette-Guérin) vaccination, years since last BCG, occupation (healthcare versus non-healthcare worker) and years of hospital employment were all significantly associated with a positive response. Rates of positive responses among employees varied greatly between hospitals (6%-35%). These differences were not explained by employee characteristics, hospital TB patient load (number of admissions or bed-days) or percentage of hospital patients from countries with high TB prevalence. The hospital with the highest rate of positive responses was notable for its lack of negative-pressure isolation rooms for TB patients.

CONCLUSIONS

Positive tuberculin responses are relatively common among hospital employees in Melbourne, with rates varying between hospitals and being higher among healthcare than non-healthcare workers. Employee characteristics, such as age, country of birth and past BCG status, explain little of this variation. More emphasis on TB infection control measures and regular staff screening may be needed.