Antituberculosis treatment-induced hepatotoxicity: role of predictive factors

Alcohol consumption as a risk factor for anti-tuberculosis drug induced liver injury: A systematic review and meta-analysis

BACKGROUND

Tuberculosis (TB) is a major infectious disease in the world, and liver injury caused by anti-tuberculosis (ATTB) drugs is an important reason for reduced patient compliance with ATTB treatment. At present, there is controversy over the role of alcohol consumption in ATTB drugs induced liver injury (ATDILI).

METHODS

All data on alcohol consumption and ATDILI were collected from PubMed, Web of Science, Scopus and Embase databases from inception to April 2023. Odds ratio (OR) and 95 % confidence interval (95 % CI) were used for statistical analysis, and Begg test and Egger test were used to evaluate publication bias.

RESULTS

A total of 1152 literatures were reviewed, and 53 literatures were included for systematic review and meta-analysis. Studies have found that alcohol consumption increases the risk of ATDILI (OR: 1.55; 95 % CI: 1.19-2.04). And an increased risk of ATDILI was found in both the alcoholic and non-alcoholic subgroups. The Begg test and Egger test showed no publication bias.

CONCLUSION

Alcohol consumption is a risk factor for ATDILI in TB patients on treatment. While on ATTB treatment, patients need to reduce alcohol consumption. More research is needed to assess the link between alcohol consumption and ATDILI.

Clinical standards for the management of adverse effects during treatment for TB

BACKGROUND: Adverse effects (AE) to TB treatment cause morbidity, mortality and treatment interruption. The aim of these clinical standards is to encourage best practise for the diagnosis and management of AE.METHODS: 65/81 invited experts participated in a Delphi process using a 5-point Likert scale to score draft standards.RESULTS: We identified eight clinical standards. Each person commencing treatment for TB should: Standard 1, be counselled regarding AE before and during treatment; Standard 2, be evaluated for factors that might increase AE risk with regular review to actively identify and manage these; Standard 3, when AE occur, carefully assessed and possible allergic or hypersensitivity reactions considered; Standard 4, receive appropriate care to minimise morbidity and mortality associated with AE; Standard 5, be restarted on TB drugs after a serious AE according to a standardised protocol that includes active drug safety monitoring. In addition: Standard 6, healthcare workers should be trained on AE including how to counsel people undertaking TB treatment, as well as active AE monitoring and management; Standard 7, there should be active AE monitoring and reporting for all new TB drugs and regimens; and Standard 8, knowledge gaps identified from active AE monitoring should be systematically addressed through clinical research.CONCLUSION: These standards provide a person-centred, consensus-based approach to minimise the impact of AE during TB treatment.

Hepatotoxicity and tuberculosis treatment outcomes in chronic liver disease

Background:

The treatment of tuberculosis (TB) is known to cause liver injury, however, there is limited data to guide optimal treatment for patients with chronic liver disease.

Methods:

We undertook a retrospective case series of patients with chronic liver disease and TB disease. The primary objective was to determine if there was a difference in the incidence of drug-induced liver injury (DILI) in patients with cirrhosis versus those with chronic hepatitis. Additionally, we sought to compare TB treatment outcomes, type and duration of therapy, and incidence of adverse events.

Results:

We included 56 patients (chronic hepatitis 40; cirrhosis 16). There were 33 patients (58.9%) who experienced DILI requiring treatment modification, with no significant difference between groups: 65% vs. 43.8%, p = 0.23. Patients with chronic hepatitis were more likely to receive treatment with standard first-line intensive phase therapy that included a combination of rifampin (RIF), isoniazid, and pyrazinamide (80.8% vs. 19.2%, p = 0.03) and any regimen than included isoniazid (92.5% vs. 68.8%, p = 0.04). The risk of DILI was higher when more hepatotoxic TB medications were used. Overall treatment success in this cohort was low (55.4%), with no significant difference between groups (62.5% vs. 37.5%, p = 0.14). Most patients with treatment success (97%) were able to tolerate a rifamycin.

Conclusions:

The risk of DILI is high, especially with the use of isoniazid, in patients with TB and chronic liver disease. This risk can be effectively mitigated with no difference in treatment outcomes in the presence of cirrhosis.

Treatment response and complications during management of Pott's spine

The global incidence of TB in 2016 was 10.4 million and India accounts for a quarter of the global burden of TB. It is estimated that there are 2.79 million people with TB in India. About 10% of extra pulmonary TB involves bone and joints. Spinal TB accounts for half the cases of skeletal TB. The incidence of spinal TB is 1-4% of total TB cases, then it is estimated that only in India approximately 60,000 spinal TB cases exist. To report the pattern of recovery and predictors of outcome of Pott's spine. The intervention comprised of four drug antitubercular treatment, rest, immobilization, and ultrasonography or computerized tomography guided aspiration or biopsy as indicated outcome measures were six months Nurick grade, and mRS and complications like drug induced hepatitis (DIH) and paradoxical worsening. Seventy-three patients with Pott's spine, median age 36 (11-73) years, 32 (43.8%) females were included. The neurological signs were present in 44 (64.4%) patients. At six months, median Nurick grade improved from 4 to 2 and;and 70% patients had a good outcome as defined by mRS.The predictors of poor outcome were weight loss, non-ambulatory state on admission and paradoxical worsening. It is concluded that neurological involvement in Pott's spine was present in 64% patients, paradoxical worsening (deterioration in symptoms after one month of ATT) in 11% and DIH in 16%. Weight loss, non-ambulatory state on admission and paradoxical worsening predicted poor outcome.

Nutrition Assessment and Adverse Outcomes in Hospitalized Patients with Tuberculosis

Background: Malnutrition in patients with tuberculosis (TB) is associated with poor outcomes. This study assessed the validity of the patient-generated subjective global assessment (PG-SGA) in adult TB patients and examined the association of the PG-SGA score with adverse outcomes. Methods: This is a retrospective chart review study compared with the well-nourished and malnourished TB patients. The nutritional status was determined using the PG-SGA for adult patients (n = 128). Clinical outcomes included liver injury and mortality. Adverse outcomes included hepatitis during anti-tuberculosis therapy. Results: By comparing nutritional status using global assessment, well-nourished patients had a significantly higher body weight index (p = 0.002), a lower PG-SGA score (p < 0.001), and lower diabetic rate (p = 0.029). Malnourishment was a risk factor (p = 0.022) for liver injury and fatal outcomes (p < 0.001). A higher PG-SGA score was a risk factor for liver injury (p = 0.002) and an independent risk factor for fatal outcomes (p = 0.031). ROC analysis for outcome prediction showed that a PG-SGA score of 5.5 points yielded the most appropriate sensitivity (61.5%) and specificity (64.7%). Conclusion: Both global assessment and the total PG-SGA score were related to tuberculosis outcome and liver injury during anti-TB treatment.

CYP2E1, GSTM1, and GSTT1 genetic polymorphisms and their associations with susceptibility to antituberculosis drug-induced liver injury in Thai tuberculosis patients

Antituberculosis drug-induced liver injury (ATDILI) is the common adverse reaction of antituberculosis drugs. Glutathione S-transferases (GSTs), which are phase II metabolizing enzymes for detoxification, are recognized as potential mediators of hepatotoxicity. However, role of GSTs polymorphisms in ATDILI pathogenesis has never been observed in Thais. This study aimed to investigate associations between GSTs and ATDILI susceptibility. This retrospective case-control multicentered study was conducted by the collaboration from ten secondary and tertiary care hospitals across Thailand, including Northern, Central, and Southern parts of Thailand. We enrolled 80 tuberculosis (TB) patients with ATDILI and 174 those without ATDILI into the study. Polymerase chain reaction (PCR) was used to determine genetic polymorphisms of GSTM1 and GSTT1 genes. CYP2E1 genotyping data were derived from microarray data. We illustrated that GSTT1 null and GSTM1/GSTT1 dual null genotypes were correlated with an increased risk of ATDILI with odds ratio (OR) at 1.83 (95% confidence interval (CI), 1.00 to 3.35; P = 0.049) and 2.12 (95%CI, 1.02 to 4.38; P = 0.044), respectively. Interestingly, GSTT1 null and GSTM1/GSTT1 dual null genotypes were found to be correlated with an increased risk of ATDILI in Thai TB patients who carried CYP2E1 wild type phenotype with OR 2.99 (95%CI, 1.07 to 8.39; P = 0.037) and 3.44 (95%CI, 1.01 to 11.71; P = 0.048), respectively. Collectively, GSTT1 null and GSTM1/GSTT1 dual null genotypes were associated with a higher risk of ATDILI in Thai TB patients, which may serve as alternative genetic biomarkers for ATDILI.

Alanine transaminase and hemoglobin appear to predict the occurrence of antituberculosis medication hepatotoxicity; findings and implications in Botswana

OBJECTIVE

Tuberculosis (TB) remains a global health problem, with medications having adverse effects including drug-induced hepatotoxicity. We determined the prevalence of anti-tuberculosis drug-induced hepatotoxicity and associated risk factors.

METHODS

Retrospective cross-sectional study in Botswana including TB patients admitted from 1 June 2017 to 30 June 2018. Anti-TB drug-induced hepatotoxicity was categorized according to WHO criteria whereas causality assessment was made according to the updated Roussel Uclaf Causality Assessment Method (RUCAM) scale. The association between hepatotoxicity and included variables was undertaken by binary logistic regression.

RESULTS

Out of 112 patient files, 15 (13.4%) developed hepatotoxicity after an average of 20.4 days from the start of treatment. Grade 3 and 4 hepatotoxicity was found in 66.7% of the cases. According to the updated RUCAM tool, 86.7% of patients were categorized as having possible anti-TB-associated hepatotoxicity. Patients with elevated baseline alanine transaminase (ALT) were more likely to develop hepatotoxicity (OR = 3.484, 95% CI = 1.02-11.90). Patients with normal hemoglobin (Hb ≥ 12 g/dl) were also more likely to develop hepatotoxicity (OR = 4.413, 95% CI = 1.160-14.8).

CONCLUSION

Overall, normal hemoglobin and elevated baseline ALT levels were significantly associated with anti-TB drug-induced hepatotoxicity. Additional research is needed to explore this association further.

Magnitude, outcome, and associated factors of anti-tuberculosis drug-induced hepatitis among tuberculosis patients in a tertiary hospital in North Ethiopia: A cross-sectional study

BACKGROUND

Short-course chemotherapy comprising isoniazid, rifampicin, ethambutol, and pyrazinamide has proved to be highly effective in the treatment of tuberculosis (TB). However, the most common adverse effect of this regimen leading to interruption of therapy is hepatotoxicity. There is a paucity of evidence in Tigray region on anti-tuberculosis drug-induced hepatitis. Therefore, this study aims to determine the magnitude, outcomes, and associated factors of drug-induced hepatitis in Ayder specialized comprehensive hospital tuberculosis clinic.

METHODS

An institution-based cross-sectional study was done on 188 cases of patients who took anti-tuberculosis drugs from August 4, 2015 to June 30, 2018 in tuberculosis clinic, Ayder Comprehensive Specialized Hospital, Northern Ethiopia. Data on socio-demography, clinical characteristics and magnitude of the incidence and outcome of anti-tuberculosis drugs-induced hepatitis were collected using structured checklist from patients' records using census method. Then, we entered and analyzed the data using statistical packages for social sciences (SPSS) statistical software version 21. Descriptive statistics were done in tables, counts, proportions, median and range. Bivariate and multivariable regression analyses were done to identify factors that are associated with drug-induced hepatitis. Confidence interval was taken at 95% and p-value of less than 0.05 was used to denote significance.

RESULTS

We approached a total of 226 patients' records, and we collected data from188 records (83.2%response rate). Anti-tuberculosis drug-induced hepatitis was found in 26 (13.8%) of the patients, of which 3 (11.54%) have died. Using multivariable logistic regression analyses, preexisting liver disease (AOR: 42.01, 95% CI: 4.22-417.49), taking other hepatotoxic drugs (AOR: 23.66, 95% CI: 1.77-314.79), and having lower serum albumin (AOR: 10.55, 95% CI: 2.57-43.32) were found to be significantly associated with the development of anti-tuberculosis drug-induced hepatitis.

CONCLUSION AND RECOMMENDATION

The incidence of anti-tuberculosis drug-induced hepatitis was high. Patients with low baseline serum albumin, taking other hepatotoxic drugs and having preexisting liver disease should be followed with serial liver enzymes after initiation of anti-tuberculosis medications. These patients should be followed with frequent measurement of liver enzymes to assess for the development of drug-induced hepatitis.

Extra-abdominal involvement is associated with antitubercular therapy-related hepatitis in patients treated for abdominal tuberculosis

AIM OF THE STUDY

Incidence and predictors of antitubercular therapy (ATT)-related hepatitis in abdominal tuberculosis are not known. The aim of the study was to identify the incidence and predictors of ATT-induced hepatitis in abdominal tuberculosis.

MATERIAL AND METHODS

A retrospective analysis of patients who received ATT for suspected abdominal tuberculosis with complete follow-up was done. We excluded patients with underlying chronic or acute liver disease necessitating an alteration in the usual ATT at start. We recorded the occurrence of ATT-induced hepatitis and compared patients with and without ATT hepatitis for any predictors of ATT-induced hepatitis.

RESULTS

Of 163 patients, 22 were excluded (17 missing information, 5 chronic liver disease). One hundred and forty-one patients (mean age: 34.33 ±15.18 years, males: 72) were included. The Mantoux test was positive in 78; 1 had HIV and 32 had an abnormal chest X-ray. Six patients had an alternative diagnosis and 11 needed surgery. Forty-nine (34.8%) had extra-abdominal involvement. Ten patients (7.1%) developed ATT-induced hepatitis. Patients with extra-abdominal tubercular involvement had a greater risk of developing ATT-induced hepatitis (p-value 0.003). None of the other parameters including hematological tests, liver function tests and biochemical parameters were different between the two groups.

CONCLUSIONS

Seven percent of patients treated for abdominal tuberculosis developed ATT hepatitis. Presence of extra-abdominal involvement was associated with ATT hepatitis.

Mechanism Investigation of Rifampicin-Induced Liver Injury Using Comparative Toxicoproteomics in Mice

Tuberculosis is one of the top causes of death among curable infectious diseases; it is an airborne infectious disease that killed 1.1 million people worldwide in 2010. Anti-tuberculosis drug-induced liver injury is the primary cause of drug-induced liver injury (DILI). Rifampicin is one of the most common anti-tuberculosis therapies and has well-known hepatotoxicity. To understand the mechanism of rifampicin-induced liver injury, we performed a global proteomic analysis of liver proteins by LC-MS/MS in a mouse model after the oral administration of 177 and 442.5 mg/kg rifampicin (LD10 and LD25) for 14 days. Based on the biochemical parameters in the plasma after rifampicin treatment, the hepatotoxic effect of rifampicin in the mouse liver was defined as a mixed liver injury. In the present study, we identified 1101 proteins and quantified 1038 proteins. A total of 29 and 40 proteins were up-regulated and 27 and 118 proteins were down-regulated in response to 177 and 442.5 mg/kg rifampicin, respectively. Furthermore, we performed Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses to characterize the mechanism of rifampicin-induced hepatotoxicity. In the molecular function category, glutathione transferase activity was up-regulated and proteins related to arachidonic acid metabolism were down-regulated. In the KEGG pathway enrichment-based clustering analysis, the peroxisome proliferator-activated receptor-γ (PPARγ) signaling pathway, cytochrome P450, glutathione metabolism, chemical carcinogenesis, and related proteins increased dose-dependently in rifampicin-treated livers. Taken together, this study showed in-depth molecular mechanism of rifampicin-induced liver injury by comparative toxicoproteomics approach.

Novel risk factors and early detection of anti tubercular treatment induced liver injury-Looking beyond American Thoracic Society Guidelines

INTRODUCTION

ATT remains the standard treatment for tuberculosis. Drug-induced liver injury (DILI) has been a long-standing concern in the treatment of tuberculosis (TB) infection.

AIMS AND OBJECTIVES

To study the occurrence and risk factors of DILI in patients on ATT by regular clinical and biochemical monitoring.

MATERIALS AND METHODS

200 patients, in whom ATT was started, were enrolled in the study. None of the patients with established risk factor for DILI as recognized by ATS guidelines was included in our study population. Regular clinical and liver function test monitoring was done at the commencement of ATT and then at 2, 4, and 8 weeks in the intensive phase subsequently at 4 and 6 months.

RESULTS

DILI developed in 16 patients. Among those, 10 patients (62.5%) developed early DILI and 6 patients (37.5%) developed late DILI. Female gender and extrapulmonary tuberculosis were found to be associated with increased risk of ATT-induced DILI, whereas age, BMI, and serum albumin were not found to significantly increase DILI risk.

CONCLUSION

DILI is a common problem among patients on ATT in our population. Early detection not only reduces the risk of developing Hepatic Failure but also prevents mortality.

A double-blinded randomized controlled trial of silymarin for the prevention of antituberculosis drug-induced liver injury

Background

Hepatitis is a common adverse effect of antituberculosis drugs. Silymarin prevented drug-induced hepatoxicity in animals with anti-oxidative mechanisms but its effect in human has been unknown. We aimed to evaluate the efficacy of silymarin for preventing antituberculosis-drug induced liver injury (antiTB-DILI) in patients with tuberculosis.

Methods

A double-blind randomized placebo-controlled trial was performed. Tuberculosis patients were randomly allocated to receive placebo or silymarin. The outcomes of interests were antiTB-DILI and the maximum liver enzymes at week 4. Antioxidative enzymes (i.e., superoxide dismutase (SOD), glutathione and malondialdehyde assays) were assessed. The risks of antiTB-DILI between the two groups were compared. A number need to treat was estimated.

Results

A total of 55 out of 70 expected numbers of patients were enrolled. There were 1/27 (3.7 %) and 9/28 (32.1 %) patients who developed antiTB-DILI in the silymarin and the placebo groups. Risk reduction was 0.28 (0.10, 0.47), i.e., receiving silymarin was 28 % at lower risk for antiTB-DILI than placebo. This led to prevention of 28 patients from being antiTB-DILI among 100 treated patients. Median (IQR) of ALT levels at week 4 in the placebo and the silymarin group were 35.0 (15, 415) IU/L and 31.5 (20, 184) IU/L (p = 0.455). The decline of SOD level at week 4 in the silymarin group was less than the placebo group (p < 0.027).

Conclusions

Silymarin reduced the incidence of antiTB-DILI. The benefit of silymarin may be explained from superoxide dismutase restoration. Larger clinical trials are required to confirm the result of our small study [Clinicaltrials.Gov Identifier Nct01800487].

Impact of glutathione S-transferase M1 and T1 on anti-tuberculosis drug-induced hepatotoxicity in Chinese pediatric patients

Background

Anti-tuberculosis drug induced hepatotoxicity (ATDH) is a major adverse drug reaction associated for anti-tuberculosis therapy. The glutathione S-transferases (GST) plays a crucial role in the detoxification of hepatotoxic metabolites of anti-tuberculosis drugs.An association between GSTM1/GSTT1 null mutations and increased risk of ATDH has been demonstrated in adults. Given the ethnic differences and developmental changes, our study aims to investigate the potential impacts of GSTM1/GSTT1genotypes on the development of ATDH in Han Chinese children treated with anti-tuberculosis therapy.

Methods

Children receiving anti-tuberculosis therapy with or without evidence of ATDH were considered as the cases or controls, respectively. The GSTM1 and GSTT1 genotyping were performed using the polymerase chain reaction.

Results

One hundred sixty-three children (20 cases and 143 controls) with a mean age of 4.7 years (range: 2 months-14.1 years) were included. For the GSTM1, 14 (70.0%) cases and 96 (67.1%) controls had homozygous null mutations. For the GSTT1, 13 (65.0%) cases and 97 (67.8%) controls had homozygous null mutations. Neither the GSTM1, nor the GSTT1 polymorphism was significantly correlated with the occurrence of ATHD.

Conclusion

Ourresults did not support the GSTM1 and GSTT1 polymorphisms as the predictors of ADTH in Chinese Han children treated with anti-tuberculosis drugs. An age-related association between pharmacogenetics and ATHD need to be confirmed in the further study.

[Tuberculosis: relevance of isoniazid dosage in prevention of liver side effects]

OBJECTIVE

Several recent studies have established a correlation between NAT2 polymorphism and hepatotoxicity induced by isoniazid. The objective of this work was to assess the place of isoniazid dosage, marker of acetylation phenotype, in clinical practice in the department of Haute-Garonne.

METHODS

Data from reportable disease of tuberculosis and the results of isoniazid dosage performed at the pharmacokinetics and clinical toxicology laboratory were used during the period 2009-2012.

RESULTS

The current practice of dosage is far from being systematical: only 3.9% of patients who developed tuberculosis have benefited from isoniazid dosage. The isoniazid initial posology was adapted to the acetylation capacity for only 33.3% of patients.

CONCLUSION

A decision tree was realized and used to identify populations (low metabolism) liable to benefit from isoniazid dosage.

Association of NAT2, GST and CYP2E1 polymorphisms and anti-tuberculosis drug-induced hepatotoxicity

Adherence to the prescribed anti-tuberculosis drug (ATD) treatment is crucial for curing patients with active TB. Anti-tuberculosis drug (ATD) induced hepatotoxicity (ATDH) may contribute to ATD's poor compliance in patients with tuberculosis (TB) as interruption of treatment and the switch to second-line anti-tuberculosis drugs, which is required in patients who do not tolerate standard drugs, may result in a sub-optimal treatment response. Isoniazid (INH) is a part of ATD and involved with ATDH due to toxic metabolites produced on its metabolism in liver, attributed to the variation in enzymes involved in this pathway like N-acetyltransferase 2 (NAT2), cytochrome P4502E1 (CYP2E1) and glutathione S-transferases (GSTs). The present study aimed at analysis of polymorphism at three loci of NAT2, two loci of GST and one locus on CYP2E1 and development of ATDH in patients undergoing ATD therapy. A total of 408 newly diagnosed patients with tuberculosis were enrolled for this study and at the end of sampling, 17 ATDH cases and 391 non-ATDH cases were reported. The genetic polymorphisms of the NAT2 and CYP2E1 genes were studied by PCR-RFLP and GSTM1 and GSTT1 were evaluated by multiplex PCR. Slow phenotype of NAT2 was found to be a risk factor for developing ATDH when compared to fast acetylators. Slow haplotype C481A590G857 and an intermediate acetylator haplotype T481A590G857 were found to be significantly associated with development of ATDH. GSTM1 and GSTT1 double null genotype was also reported to be associated with ATDH development. The heterozygote genotype 'c1c2' of CYP2E1 was also seen to contribute towards elevated risk of ATDH. 'c2' allele absence in females ATDH group can be considered as a protective factor against development of ATDH. In males, presence of 'c1c2' allele was seen to contribute towards elevated risk of ATDH development.

Association of N-acetyltransferase 2 and cytochrome P450 2E1 gene polymorphisms with antituberculosis drug-induced hepatotoxicity in Western India

BACKGROUND AND AIM

Tuberculosis (TB) is a major public health problem in India. Despite the treatment availability and monitoring, drug-induced hepatotoxicity (DIH) is a serious concern and can lead to discontinuation of treatment. Anti-TB DIH is well known and can aggravate because of pharmacokinetic and pharmacodynamic interactions. Genetic polymorphism in the drug-metabolizing enzyme genes is an important factor that predisposes certain fraction of the population to drug-induced toxicity. The purpose of this study was to assess the association of N-acetyltransferase 2 (NAT2) and cytochrome P450 2E1 (CYP2E1) gene polymorphism with anti-TB DIH in Western Indian population.

METHODS

A prospective cohort study of 215 patients taking treatment against TB was performed. The NAT2 and CYP2E1 genotypes were determined using polymerase chain reaction and restriction fragment length polymorphism methods. Logistic regression model was used to calculate odds ratio at 95% confidence interval and their respective P values.

RESULTS

The risk of anti-TB DIH was significantly higher in slow acetylator (SA) than in intermediate and rapid acetylator of NAT2 genotypes (odds ratio: 2.3, P = 0.01). We also observed the homozygous point mutation at position 481, associated with higher risk of hepatotoxicity (P < 0.01). The major haplotype NAT2*4 seems to provide protection in DIH compared with non-DIH TB patients (P = 0.04). However, we did not find a significant association between CYP2E1 genotypes and anti-TB DIH.

CONCLUSION

Increased susceptibility to isoniazid (INH)-induced hepatotoxicity due to presence of NAT2 SA polymorphism was demonstrated in Western Indian population. NAT2 genotyping can therefore serve as an important tool for identifying patients predisposed to anti-TB DIH.

Feasibility of a fixed-dose regimen of pyrazinamide and its impact on systemic drug exposure and liver safety in patients with tuberculosis

Historically, dosing regimens for the treatment of tuberculosis (TB) have been proposed in an empirical manner. Dose selection has often been the result of efficacy trials in which drugs were administered regardless of the magnitude of the effect of demographic factors on drug disposition. This has created challenges for the prescription of fixed-dose combinations with novel therapeutic agents. The objectives of this investigation were to evaluate the impact of body weight on the overall systemic exposure to pyrazinamide (PZA) and to assess whether the use of one fixed dose, without adjustment according to weight, would ensure target exposure and safety requirements across the overall patient population. Using a population pharmacokinetic model, simulation scenarios were explored based on population demographics from clinical trials in TB patients and on historical hepatotoxicity data. The systemic drug exposure (area under the concentration-time curve [AUC]), peak concentrations (the maximum concentration of drug in serum [C(max)]), the time above the MIC (t > MIC), and the risk of hepatotoxicity were evaluated for the current weight-banded regimen and compared to fixed doses under the assumption that pharmacokinetic differences are the primary drivers of toxicity. Evaluation of the standard weight banding reveals that more than 50% of subjects in the weight range of 45 to 55 kg remain below the proposed target exposure to PZA. In contrast, the use of a fixed 1,500-mg dose resulted in a lower proportion of subjects under the target value, with a 0.2% average overall increase in the risk of hepatotoxicity. Our results strongly support the use of a fixed-dose regimen for PZA in coformulation or combination with novel therapeutic agents.

Genetic polymorphisms of NAT2, CYP2E1 and GST enzymes and the occurrence of antituberculosis drug-induced hepatitis in Brazilian TB patients

Isoniazid (INH), one of the most important drugs used in antituberculosis (anti-TB) treatment, is also the major drug involved in hepatotoxicity. Differences in INH-induced toxicity have been attributed to genetic variability at several loci, such as NAT2, CYP2E1, GSTM1 and GSTT1, that code for drug-metabolising enzymes. Our goal was to examine the polymorphisms in these enzymes as susceptibility factors to anti-TB drug-induced hepatitis in Brazilian individuals. In a case-control design, 167 unrelated active tuberculosis patients from the University Hospital of the Federal University of Rio de Janeiro, Brazil, were enrolled in this study. Patients with a history of anti-TB drug-induced acute hepatitis (cases with an increase to 3 times the upper limit of normal serum transaminases and symptoms of hepatitis) and patients with no evidence of anti-TB hepatic side effects (controls) were genotyped for NAT2, CYP2E1, GSTM1 and GSTT1 polymorphisms. Slow acetylators had a higher incidence of hepatitis than intermediate/rapid acetylators [22% (18/82) vs. 9.8% (6/61), odds ratio (OR), 2.86, 95% confidence interval (CI), 1.06-7.68, p = 0.04). Logistic regression showed that slow acetylation status was the only independent risk factor (OR 3.59, 95% CI, 2.53-4.64, p = 0.02) for the occurrence of anti-TB drug-induced hepatitis during anti-TB treatment with INH-containing schemes in Brazilian individuals.

Rifampicin-isoniazid induced fatal fulminant hepatitis during treatment of latent tuberculosis: A case report and literature review

A 42-year-old Indian man received 450 mg rifampicin (RIF) and 150 mg isoniazid (INH) daily after being diagnosed of a latent tuberculosis infection. Baseline serum aminotransferase and total bilirubin levels were within normal limits. On day 31 of treatment, the patient experienced epigastric discomfort and general malaise and one week later he developed nausea and episodic vomiting. The patient missed his first scheduled clinic appointment and he continued taking RIF-INH despite his symptoms. He visited the tuberculosis clinic on day 47 of treatment where he was found to be jaundiced and his liver enzymes were elevated. RIF-INH was stopped and the patient was admitted to our hospital as a case of RIF-INH induced hepatitis. On the 7th day of hospitalization, the patient developed consciousness disturbance with flapping tremor and high ammonia level. The patient was diagnosed with fulminant hepatic failure and transferred immediately to the medical intensive care unit, where he died 4 days later.

Tuberculosis chemotherapy in the 21 century: Back to the basics

The key to successful elimination of tuberculosis (TB) is treatment of cases with optimum chemotherapy. Poor chemotherapy over time has led to drug-resistant disease. Drug resistance of Mycobacterium tuberculosis develops by the selective growth of resistant mutants. The incidence of drug-resistant cases depends on the number of bacilli and the drug-resistant mutants in the lesion. The latter is low for individual drugs and even lower for two and three drugs. Therefore, use of combination chemotherapy with three or more drugs results in cure. However, irregular treatment, inadequate drugs, inadequate drug doses or addition of a single drug to a failing regimen allows selective growth of resistant mutants and acquired drug-resistant TB. Contacts of these resistant cases develop primary drug resistant TB. Thus, drug resistance in tuberculosis is a "man-made problem". Anti-TB chemotherapy must be given optimally by (i) ensuring adequate absorption of drugs, (ii) timely diagnosis and management of drug toxicities and (iii) treatment adherence. New classes of anti-TB drugs are needed; but are unlikely to become available soon. It is vital that the 21(st) century physicians understand the basic principles of TB chemotherapy to ensure efficient use of available drugs to postpone or even reverse epidemics drug-resistant TB.

Hepatic safety of antibiotics used in primary care

Antibiotics used by general practitioners frequently appear in adverse-event reports of drug-induced hepatotoxicity. Most cases are idiosyncratic (the adverse reaction cannot be predicted from the drug's pharmacological profile or from pre-clinical toxicology tests) and occur via an immunological reaction or in response to the presence of hepatotoxic metabolites. With the exception of trovafloxacin and telithromycin (now severely restricted), hepatotoxicity crude incidence remains globally low but variable. Thus, amoxicillin/clavulanate and co-trimoxazole, as well as flucloxacillin, cause hepatotoxic reactions at rates that make them visible in general practice (cases are often isolated, may have a delayed onset, sometimes appear only after cessation of therapy and can produce an array of hepatic lesions that mirror hepatobiliary disease, making causality often difficult to establish). Conversely, hepatotoxic reactions related to macrolides, tetracyclines and fluoroquinolones (in that order, from high to low) are much rarer, and are identifiable only through large-scale studies or worldwide pharmacovigilance reporting. For antibiotics specifically used for tuberculosis, adverse effects range from asymptomatic increases in liver enzymes to acute hepatitis and fulminant hepatic failure. Yet, it is difficult to single out individual drugs, as treatment always entails associations. Patients at risk are mainly those with previous experience of hepatotoxic reaction to antibiotics, the aged or those with impaired hepatic function in the absence of close monitoring, making it important to carefully balance potential risks with expected benefits in primary care. Pharmacogenetic testing using the new genome-wide association studies approach holds promise for better understanding the mechanism(s) underlying hepatotoxicity.

Blood levels of pyrazinamide in children at doses administered under the Revised National Tuberculosis Control Program

OBJECTIVES

To evaluate the blood levels, pharma-cokinetics and pharmacodynamic indices of pyrazinamide (PZA) in children suffering from tuberculosis, at doses administered under the weight band system of Revised National Tuberculosis Control Program of India (RNTCP) of India.

DESIGN

Prospective, open-label, non-randomized single-dose study.

SETTING

20 children in the age group 5-12 years attending out-patient tuberculosis clinic of a tertiary hospital.

OUTCOME MEASURES

Blood levels of pyrazinamide after single dose administration, as per the weight band system of RNTCP.

RESULTS

Group I (n=7) included children who received pyrazinamide within the recommended 30-35 mg/kg dose (mean 31.9 ± 0.8 mg/kg) and Group II (n=13) included those who received a dose lower than 30 -35 mg/kg (mean 28.1 ± 0.3 mg/kg). The Cmax (95% CI of difference 2.2, 13.2; P=0.008) and AUC (95% CI of difference 28.6, 208.1; P=0.01) were significantly lower in Group II. The duration of time for which the concentration was maintained above 25 ug ml-1 was 4-8 h in Group I and 3-5.5 h in Group II (95% CI of difference 0.1, 2.0; P=0.03). The half life, elimination rate constant, clearance and volume of distribution were comparable in the two groups. The ratios of Cmax and AUC to MIC (25 ug ml-1) in children were lower than that recommended for PZA in adults.

CONCLUSIONS

Lower blood concentrations are being attained in children receiving PZA doses under the existing weight band system of RNTCP of India. The weight bands may need to be revised and dose recommendations be based on pharmacokinetic and efficacy data in children.

Antituberculosis Drug-Induced Hepatotoxicity in IranianTuberculosis Patients: Role of Isoniazid Metabolic Polymorphism

The aim of this study was to determine the association of n-acetyltransferase-2 polymorphisms and anti-tuberculosis drug-induced hepatotoxicity in Iranian pulmonary tuberculosis patients. Acetylating phenotypes was studied in 50 Iranian pulmonary tuberculosis patients using metabolic ratio of plasma acetyl-Isoniazid to Isoniazid. The association between hepatotoxicity and the n-acetyltransferase-2 phenotype was evaluated by using the chi-square (x(2)) test. The metabolic ratio had a bimodal distribution with an antimode value of 1.0. Based on the metabolic ratio of the mentioned patients, 20 (40%) were slow acetylators and 30 (60%) were fast ones. Hepatotoxicity was manifested in 9 of 20 slow acetylators (45%) and only in 5 of 30 rapid acetylators (16.7%). There was a significant difference in the frequency of hepatotoxicity between the slow and fast acetylators (x(2) = 4.778, and p = 0.03). Sex and age were not found to be risk factors for hepatotoxicity. Our findings show that slow acetylation profile is significantly associated with a higher risk of developing hepatotoxicity due to the anti-TB drugs in Iranian pulmonary tuberculosis patients.

Hepatotoxic effects of therapies for tuberculosis

Hepatotoxic effects attributable to antituberculosis therapy are considered unique among drug-related liver problems because almost all first-line antituberculosis medications have such adverse effects, which vary in severity according to the drug and the regimen. In addition, all regimens for the treatment of active tuberculosis include a combination of medications that must typically be administered for at least 6 months to ensure complete cure of the disease and to minimize the development of drug-resistant bacterial strains. Hepatotoxic effects are a serious problem in patients who are undergoing treatment for tuberculosis, not only because of the morbidity and mortality they directly cause, but also because the liver symptoms can necessitate interruption of therapy or affect a patient's adherence to it, which can limit the efficacy of the antitubercular regimen.

Weight loss during tuberculosis treatment is an important risk factor for drug-induced hepatotoxicity

The objective of this study was to determine the association between weight loss and drug-induced hepatotoxicity (DIH). A retrospective observational study of 192 active tuberculosis (TB) patients consecutively admitted in a tertiary referral TB centre in the Netherlands was conducted. The outcome measure for DIH was defined as hepatotoxicity necessitating interruption of anti-TB drugs. Multivariate logistic regression analysis on interruption of anti-TB drugs was performed, with age, sex, nutritional status, TB disease severity, drug resistance, comorbidity including baseline liver function tests, anti-TB drug regimen, co-medication and addictions as independent risk factors. Anti-TB drugs were interrupted in thirty-one patients (16·1%). The most important risk factor was weight loss of 2 kg or more within 4 weeks during TB treatment (OR 211, 95% CI 36·0, 1232). Other independent risk factors were infection with hepatitis C (OR 19·6, 95% CI 2·4, 164), age over 60 years (OR 18·5, 95% CI 2·3, 151) and multi-drug-resistant TB (OR 8·2, 95% CI 1·3, 53·6). This study shows that weight loss during TB treatment was the most important risk factor for DIH necessitating interruption of anti-TB drugs. Causes of weight loss during TB treatment and the association between weight change and hepatotoxicity need further investigation.

Genetic polymorphisms of cytochrome P450 and glutathione S-transferase associated with antituberculosis drug-induced hepatotoxicity in Chinese tuberculosis patients

This study was designed to investigate the association of genetic polymorphisms of cytochrome P450 subtype 2E1 (CYP2E1) and glutathione S-transferase mu 1 (GSTM1) with susceptibility to antituberculosis drug-induced hepatotoxicity (ADIH) in Chinese tuberculosis patients. All patients were treated with a combination of isoniazid, rifampicin, pyrazinamide and ethambutol. Genomic DNA from 104 patients with ADIH and 111 without ADIH was analysed for the frequency of CYP2E1 RsaI and GSTM1 RsaI genotypes by polymerase chain reaction and restriction fragment length polymorphism. The association of polymorphisms with susceptibility to ADIH was calculated using the chi(2)-test and logistic regression analysis. The CYP2E1 RsaI polymorphisms were significantly associated with ADIH and the c1/c1 genotype was an independent risk factor for ADIH. Compared with the GSTM1 RsaI present genotype, the GSTM1 RsaI null genotype tended to increase susceptibility to ADIH, but the association with ADIH was not significant. The results indicate that CYP2E1 RsaI genotype c1/c1 is a potential risk factor for ADIH in the Chinese population. The tendency of the GSTM1 RsaI null genotype to increase susceptibility to ADIH needs further study.

Drug-drug interactions of silymarin on the perspective of pharmacokinetics

Silymarin, which is extracted from the milk thistle (Silybum marianum), has been used for centuries for treating hepatic disorders and its hepatoprotective effects have been known for hundreds of years. Silymarin is a mixture of polyphenoic flavonoids, which include silibinin (silybin A and silybin B), isosilyin A and B, silychristin A and B, silydianin and other phenol compounds. The pharmacokinetics of silibinin shows fast absorption and elimination. Silymarin undergoes phase I and phase II metabolism, especially phase II conjugation reactions, it undergoes multiple conjugation reactions, and is primarily excreted into bile and urine. Silymarin has a good safety profile, but little is known regarding its potential for drug interaction. Silymarin has limited effect on the pharmacokinetics of several drugs in vivo; despite silymarin decreasing the activity of cytochrome P-450 (CYPs) enzymes, UDP-glucuronosyltransferase (UGT) enzyme, and reducing P-glycoprotein (P-gp) transport. Health-care practitioners should caution patients against co-administration of silymarin and pharmaceutical drugs.

Effect of silibinin on the pharmacokinetics of pyrazinamide and pyrazinoic acid in rats

Pyrazinamide (PZA) is widely used in combination with other drugs in chemotherapy for tuberculosis. However, the dose-related liver injury is the main adverse effect of PZA and its metabolite [pyrazinoic acid (PA)]. Silibinin is the main flavonoid extracted from milk thistle (Silybum marianum), and it displays hepatoprotective properties. This study investigates the pharmacokinetics of PZA and PA and their interaction with silibinin in rats. The parallel study design was divided into six groups: PZA alone, PZA + long-term silibinin exposure, PZA + concomitant short-term silibinin exposure, PA alone, PA + long-term silibinin exposure, and PA + concomitant short-term silibinin exposure groups. The results indicate that the distribution ratio of PZA from bile to blood [area under the curve (AUC)(bile)/AUC(blood)] in the PZA + long-term silibinin exposure and PZA + concomitant short-term silibinin exposure groups was also not significantly different when compared with the PZA alone group. However, the bile-to-blood distribution ratio of PA was significantly decreased in the PA + long-term silibinin exposure and the PA + concomitant short-term silibinin exposure groups. On PZA administration, the blood, but not bile, levels of PA were markedly increased in the PZA + long-term silibinin exposure and PZA + concomitant short-term silibinin exposure groups, but the bile-to-blood ratio of PA was decreased. These results suggest that the excretion pathway of PA may be blocked by silibinin through xanthine oxidase and hepatobiliary excretion.

Antituberculosis drugs and hepatotoxicity

Isoniazid, pyrazinamide and rifampicin have hepatotoxic potential, and can lead to such reactions during antituberculosis chemotherapy. Most of the hepatotoxic reactions are dose-related; some are, however, caused by drug hypersensitivity. The immunogenetics of antituberculosis drug-induced hepatotoxicity, especially inclusive of acetylaor phenotype polymorphism, have been increasingly unravelled. Other principal clinical risk factors for hepatotoxicity are old age, malnutrition, alcoholism, HIV infection, as well as chronic hepatitis B and C infections. Drug-induced hepatic dysfunction usually occurs within the initial few weeks of the intensive phase of antituberculosis chemotherapy. Vigilant clinical (including patient education on symptoms of hepatitis) and biochemical monitoring are mandatory to improve the outcomes of patients with drug-induced hepatotoxicity during antituberculosis chemotherapy. Some fluoroquinolones like ofloxacin/levofloxacin may have a role in constituting non-hepatotoxic drug regimens for management of tuberculosis (TB) in the presence of hepatic dysfunction. Isoniazid administration is currently the standard therapy for latent TB infection. Rifamycins like rifampicin or rifapentine, alone or in combination with isoniazid, may also be considered as alternatives, pending accumulation of further clinical data. During treatment of latent TB infection, regular follow up is essential to ensure adherence to therapy and facilitate clinical monitoring for hepatic dysfunction. Monitoring of liver chemistry is also required for those patients at risk of drug-induced hepatotoxicity.

Risk Factors of Hepatotoxicity During Anti-tuberculosis Treatment

BACKGROUND

Antituberculosis treatment (ATT) induced hepato-toxicity is common, but risk factors predicting its development are poorly understood. The present study evaluates the clinical risk factors predicting the development of hepatotoxicity in Indian patients with tuberculosis on antituberculosis treatment.

METHODS

Three groups of patients were studied at three service hospitals over a 3 year period from 2000-2002. Patients given ATT were followed up with monthly LFTs. Consecutive patients who developed Liver dysfunction (rise in SGPT > 5 times upper limit of normal) were studied, along with matched controls who did not. Markers for hepatitis B were also noted in these patients once in 6 months. A third group of patients who did not receive ATT but were HBsAg positive, were also similarly followed up. The possible association of age and sex of the patient, alcoholism, unrecognized chronic liver disease, hepatitis B virus carrier status and nutritional status with ATT-induced hepatitis was assessed. Statistical analysis was carried out by Chi square test/Fisher's exact test using WHO provided software Epi Info 6. Sixty-nine patients with ATT-induced hepatotoxicity were prospectively studied. In addition 128 patients on anti-tuberculosis drugs without hepatotoxicity and 39 HBsAg carriers not on ATT were followed up for 1 year.

RESULTS

Age, Sex, history of alcohol intake and BMI were not found to be related to development of hepatotoxicity. Presence of HBV infection or an underlying silent chronic liver disease were found to significantly increase the risk of development of ATT-induced hepatotoxicity. Continuation of ATT after development of jaundice was associated with a high fatality rate. It was possible to re-introduce isoniazid in 96% and rifampicin in 88% of patients with ATT induced hepatotoxicity.

CONCLUSION

ATT-induced hepatitis is common and is potentially fatal. It is likely to occur in those with underlying silent chronic liver disease, HBV infection and have been given ATT without a definite evidence of tuberculosis. Discontinuation of ATT leads to rapid recovery in most cases and drugs can safely be introduced after recovery in a majority of cases.

Monitoring and management of antituberculosis drug induced hepatotoxicity

BACKGROUND

Hepatotoxicity to antituberculosis therapy (ATT) poses a major challenge. This often results in inadequate therapy. The risk of fulminant hepatic failure and mortality is high once icteric hepatitis develops. There is no consensus on monitoring protocols and for the reintroduction of ATT.

METHODS

All patients (from the Department of Internal Medicine and Gastroenterology, Jagjivanram Hospital and the Department of Gastroenterology, Bombay Hospital, Mumbai, India) with a diagnosis of tuberculosis, who were to receive ATT during the study period, were included in the present study for prospective periodic laboratory monitoring for the development of hepatotoxicity. Those patients who developed hepatotoxicity formed Group A (n = 21), whereas those who did not develop hepatotoxicity were included in Group C (n = 179). For the purpose of comparison with Group A, all the patients who presented directly with ATT induced hepatotoxicity during the study period were categorized as Group B (n = 24). Group A and B were further studied after normalization of liver functions for sequential reintroduction with therapeutic doses at a weekly interval.

RESULTS

In Group A, 66.6% (14 patients) of the patients were diagnosed in the asymptomatic period. Seven patients had symptomatic hepatitis, but none had icteric illness. There were no mortalities in Group A. In contrast, all the patients in Group B had symptomatic hepatitis (75% icteric hepatitis). There was a mortality rate of 16.6% (four patients). Of the 41 patients from Groups A and B who survived, reintroduction was successful in 38/39 (97.4%). In the remaining two patients who were in Group B, reintroduction was not attempted because of decompensated liver disease.

CONCLUSIONS

Periodic laboratory monitoring is important in detecting hepatotoxicity at an early stage, thereby preventing mortality. Sequential reintroduction is often successful.

Isoniazid- and rifampicin-induced oxidative hepatic injury--protection by N-acetylcysteine

The role of N-acetylcysteine (NAC), a glutathione (GSH) precursor, was investigated in protection against isoniazid- (INH) and rifampicin- (RIF) induced oxidative hepatic injury in young Wistar rats. The hepatotoxic dose of INH and RIF was 50 mg kg(-1) day(-1) each and the hepatoprotective dose of NAC was 100 mg kg(-1) day(-1). All drugs were administered intraperitoneally (i.p.) in sterile water (4.0 ml kg(-1) day(-1)) over a period of 3 weeks. Status of oxidative/antioxidative profiles was the mechanistic approach to assess the hepatotoxicity and/or hepatoprotection. The oxidative injury in INH-RIF co-exposed animals was closely associated with significant decline of GSH and related thiols, as well as with compromised antioxidant enzyme system. The oxidative stress was further supported by increased lipid peroxidation observed in these animals. The co-administration of NAC prevented the induction of oxidative stress in INH-RIF co-exposed animals. The amelioration of oxidative stress by NAC was faithfully reflected as normal morphology in these animals, except the presence of mild degree of portal triaditis in one animal co-exposed to INH-RIF and NAC. In contrast, the animals co-exposed to INH-RIF alone showed histological lesions which ranged from intralobular inflammation to patchy necrosis. These results suggest that INH-RIF-induced oxidative injury can be prevented by supporting the cellular antioxidant defense mechanism by NAC.

Hepatic enzyme abnormalities in children on triple therapy for tuberculosis

Standard chemotherapy for tuberculosis (TB) in children uses hepatotoxic drugs. Published data and guidelines on monitoring of liver function during TB treatment are often contradictory and not directly relevant to the pediatric population. We carefully monitored 43 children (age 6.6 years, 0.7-15.1 [median, range]; 49% male; 72% Caucasian) being treated for TB infection (n = 8) or disease (n = 35) with triple therapy, using pyrazinamide, rifampicin, and isoniazid in standard recommended doses. Children on other hepatotoxic drugs were excluded. Measurements of liver function tests (LFT) included aspartate transaminase (AST), alanine transaminase (ALT), and bilirubin, and they were checked before and a median of 5 times (1-23) during treatment. Only one child had mildly abnormal LFTs pretreatment. Thirteen children (n = 13, [30%]; age 7.6 years, 1.8-10.9; 54% male; 77% Caucasian) developed abnormal LFTs (> mean + 2 SD) and of these 10 had TB disease. Eight of the 13 had mildly elevated enzymes (< twice upper limit of normal) while in five, all with disease, the enzymes were more markedly raised. In the group with normal LFTs (n = 30, [70%]; age 6.6 years 0.7-15.1; 47% male; 70% Caucasian) 25 had disease (83%). Liver enzyme elevation occurred early (1.65 weeks, 0.6-16.6). Only two children had symptoms (one jaundice, one pruritus) with treatment being stopped temporarily only in the jaundiced child. Otherwise, LFTs normalized without interrupting treatment. We conclude that elevated liver enzymes are not uncommon in children receiving triple therapy for TB, generally occurring early in treatment. Symptoms are rare. Current British Thoracic Society and American Thoracic Society guidelines (that if LFTs are normal prior to treatment then further monitoring should only be performed if clinically indicated) seem adequate for children.

Hepatotoxicity of antitubercular treatments. Rationale for monitoring liver status

The standard antitubercular regimen currently includes a combination of 3 antitubercular agents: isoniazid, rifampicin (rifampin) and pyrazinamide. Administration of a fourth agent, ethambutol, is recommended when isoniazid resistance is suspected. Two of these 4 agents (isoniazid and pyrazinamide) are major hepatotoxins. The remaining 2 agents (rifampicin and ethambutol) are rarely or not hepatotoxic. However, rifampicin, which is a powerful enzyme inducer, may enhance the hepatotoxicity of isoniazid. In patients receiving a combination of isoniazid, rifampicin and pyrazinamide, 2 patterns of fulminant liver injury can be observed. The first pattern is characterised by an increase in serum transaminase activity that occurs soon (usually within the first 15 days) after initiation of treatment. This pattern is likely to be caused by rifampicin-induced isoniazid hepatotoxicity. The prognosis is good in most cases. The second pattern is characterised by an increase in serum transaminase activity that occurs late (usually more than 1 month) after the initiation of treatment. It has been suggested that this pattern may be related to pyrazinamide hepatotoxicity. The prognosis of this type of hepatitis is generally poor. In order to reduce the risk of severe hepatic adverse effects during antitubercular treatment, several measures are proposed. First, patients with underlying liver test abnormalities should not be given pyrazinamide. Second, isoniazid and pyrazinamide should be administered at the lowest dosage within their respective therapeutic ranges. Third, serum transaminase levels should be determined twice weekly during the first 2 weeks of treatment, every 2 weeks during the rest of the first 2 months, and every month thereafter. When serum transaminase levels increase to greater than 3 times the upper limit of normal, therapy with isoniazid, rifampicin and pyrazinamide should be stopped. After serum transaminase levels have returned to normal, isoniazid can be re-introduced at a low daily dose, without rifampicin. Pyrazinamide may not be re-introduced because of the risk of recurrence and the poor prognosis of pyrazinamide-induced hepatitis. Although it is nephrotoxic, streptomycin is an alternative in patients with liver test abnormalities during antitubercular treatment.

Hepatotoxicity due to antituberculosis therapy. Clinical profile and reintroduction of therapy

The clinical profile of antituberculosis treatment (ATT)-induced hepatotoxicity is variable, and the reintroduction of ATT in patients who have developed such injury is controversial. We conducted a prospective study to determine the clinical profile in patients with ATT-induced hepatotoxicity and to test a predefined strategy of reintroduction of ATT. Seventy-two consecutive patients with clinical evidence of ATT-induced hepatotoxicity were included. Jaundice was the presenting symptom in 44 (61%) patients; prodromal symptoms were present in 28 (39%). Serious complications developed in 12 (16.6%) patients (fulminant hepatic failure in seven, subacute hepatic failure in four, hepatic encephalopathy in one). Nine patients (three males, six females) died from these complications. The mean duration of treatment before the onset of hepatitis was significantly longer in the group that died (53.22 +/- 36.22 days) than in the rest of the patients (31.07 +/- 30.30 days; p < 0.01). Malnutrition was present in 37 of the 72 patients. After resolution of drug induced hepatitis, reintroduction of isoniazid and rifampicin was possible in 41 of 44 patients. Thus, our results showed that ATT-induced hepatitis carried significant morbidity and mortality, that malnutrition was common in patients with ATT-related hepatitis, and that potentially hepatotoxic antituberculosis agents could be safely reintroduced after recovery from hepatitis.