Aging and hepatotoxicity of isoniazid and rifampin in pulmonary tuberculosis

Co-infection with hepatitis B virus among tuberculosis patients is associated with poor outcomes during anti-tuberculosis treatment

BACKGROUND

Tuberculosis (TB) and chronic Hepatitis B virus (HBV) infection are common in China. Fist-line anti-TB medications often produce drug-induced liver injury (DILI). This study sought to investigate whether TB patients with chronic HBV co-infection are more susceptible to liver failure and poor outcomes during anti-TB treatment.

METHODS

Eighty-four TB patients developed DILI during anti-TB treatment and were enrolled, including 58 with chronic HBV co-infection (TB-HBV group) and 26 with TB mono-infection (TB group). Clinical data and demographic characteristics were reviewed. The severity of DILI and incidences of liver failure and death were compared. Risk factors of clinical outcomes were defined.

RESULTS

The patterns of DILI were similar in both groups. Compared with patients in the TB group, patients in the TB-HBV group who did not receive anti-HBV therapy before anti-TB treatment were more susceptible to Grade-4 severity of DILI (36.2% vs. 7.7%, P = 0.005), liver failure (67.2% vs. 38.5%, P = 0.013) and poor outcomes (37.9% vs. 7.7%, P = 0.005). Age > 50 years (48.1% vs. 22.6%, P = 0.049), cirrhosis (50.0% vs. 15.4%, P = 0.046) and total bilirubin > 20 mg/dl (51.6% vs. 14.8%, P = 0.005) were independent risk factors for the rate of death in the TB-HBV group, and HBV DNA > 20,000 IU/ml had borderline significance (44.1% vs. 20.8%, P = 0.081). In the TB-HBV group, nucleos(t)ide analogues as rescue therapy were not able to reduce short-term death (33.3% vs. 36.8%, P = 0.659) once liver failure had occurred.

CONCLUSIONS

Patients on anti-TB therapy with chronic HBV co-infection are more susceptible to developing liver failure and having poor outcomes during anti-TB treatment. Regular monitoring of liver function and HBV DNA level is mandatory. Anti-HBV treatment should be considered in those with high viral levels before anti-TB treatment.

Mitochondrial dysfunction as a mechanism of drug-induced hepatotoxicity: current understanding and future perspectives

Mitochondria are critical cellular organelles for energy generation and are now also recognized as playing important roles in cellular signaling. Their central role in energy metabolism, as well as their high abundance in hepatocytes, make them important targets for drug-induced hepatotoxicity. This review summarizes the current mechanistic understanding of the role of mitochondria in drug-induced hepatotoxicity caused by acetaminophen, diclofenac, anti-tuberculosis drugs such as rifampin and isoniazid, anti-epileptic drugs such as valproic acid and constituents of herbal supplements such as pyrrolizidine alkaloids. The utilization of circulating mitochondrial-specific biomarkers in understanding mechanisms of toxicity in humans will also be examined. In summary, it is well-established that mitochondria are central to acetaminophen-induced cell death. However, the most promising areas for clinically useful therapeutic interventions after acetaminophen toxicity may involve the promotion of adaptive responses and repair processes including mitophagy and mitochondrial biogenesis, In contrast, the limited understanding of the role of mitochondria in various aspects of hepatotoxicity by most other drugs and herbs requires more detailed mechanistic investigations in both animals and humans. Development of clinically relevant animal models and more translational studies using mechanistic biomarkers are critical for progress in this area.

Relevance for patients:This review focuses on the role of mitochondrial dysfunction in liver injury mechanisms of clinically important drugs like acetaminophen, diclofenac, rifampicin, isoniazid, amiodarone and others. A better understanding ofthe mechanisms in animal models and their translation to patients will be critical for the identification of new therapeutic targets.

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.

Hepatotoxicity from antituberculous therapy in the elderly: a systematic review

BACKGROUND

Elderly persons have the highest rates of tuberculosis (TB) in the United States compared to all other age groups. A systematic literature review was conducted to determine if older age was a risk factor for hepatotoxicity resulting from treatment with first-line drugs used to treat active (TB) and latent tuberculosis (LTBI).

METHODS

A systematic review of MEDLINE, Cochrane Controlled Trial Registry, CINAHL(®), and Science Citation Index Expanded (from 1970 to 2011) was performed to determine the risk of hepatotoxicity, comparing those over 60 with those under 60. A meta-analysis was performed using a random effects model along with log odds ratios and the chi-square test.

FINDINGS

Thirty-eight studies (40,034 participants; 1208 cases of hepatotoxicity) met the selection criteria. For active TB, an overall mean effect of 0.277 (p = 0.024, 95% CI: 0.037-0.517) was observed, which is equivalent to an odds ratio of 1.32 (95% CI: 1.04-1.68). For LTBI, an overall mean effect of 1.42 (p < 0.001, 95% CI: 0.794-2.05) was observed, which translates to an odds ratio of 4.14 (95% CI: 2.21-7.74).

INTERPRETATION

Our analysis revealed that patients older than 60 had significantly more risk of hepatotoxicity. These studies suggest that a gentler regimen of treatment for older individuals could benefit health outcomes in this population of TB patients and minimize risks to the public's health.

Drug-induced liver injury in the elderly

Historically, the elderly have been considered to be at increased risk for drug-induced liver injury (DILI). Animal studies have demonstrated changes in hepatic physiology that affect drug metabolism in the aging liver; however, there is no evidence that this leads to any appreciable deterioration of liver function in healthy older humans. Updated data from international DILI registries give us pause to consider whether the elderly are truly at increased risk to develop hepatic injury. Instead, hepatotoxicity in the elderly appears to be more a function of drug exposure, polypharmacy and drug-drug interactions. Isoniazid and benoxaprofen are the only two agents with a well-studied correlation between increasing age and risk of DILI. Nevertheless, given the increasing proportion of patients over age 65 in the U.S. and abroad, the influence of age on the risk of DILI is the focus of this review.

Severe hepatic complications of antituberculous therapy

Hepatotoxicity from antituberculous therapy is well described, but fortunately severe complications are rare. The optimal methods of monitoring for significant hepatotoxicity while on treatment are uncertain. Some authorities recommend measuring liver enzymes only if symptoms develop, whereas others recommend regular liver enzyme monitoring throughout the course of therapy. In British Columbia, from 1990 to 1997, 2624 active and approximately 8000 chemoprophylaxis cases have been treated, but only two severe complications directly related to antituberculous therapy have occurred. A 33-year-old male developed fulminant hepatic failure seven months after starting isoniazid chemoprophylaxis and required a liver transplant. The other patient died from hepatic failure that developed in the first month of triple-drug therapy for proven active pulmonary tuberculosis. The early and late onset of hepatic failure associated with antituberculous therapy in these cases underline the difficulties in identifying a monitoring protocol that will totally negate the risk of severe complications.

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.

[Adverse effects of the new tuberculosis treatment regimen recommended by the Brazilian Ministry of Health]

OBJECTIVE

To determine the principal adverse effects of the tuberculosis treatment regimen recommended by the Brazilian Ministry of Health.

METHODS

A prospective descriptive study involving 79 tuberculosis patients treated at the Clinical Research Center of the Cassiano Antonio Moraes University Hospital, in the city of Vitória, Brazil, between 2003 and 2006. The treatment regimen consisted of isoniazid, rifampicin, pyrazinamide and ethambutol for four months, followed by rifampicin and isoniazid for two months. During the treatment period, the patients were clinically evaluated every week and had a monthly medical visit.

RESULTS

The overall incidence of adverse effects was 83.54%. Articular/bone/muscle involvement was the most common, followed by skin involvement (24.94% and 22.09%, respectively). Adverse effects were more common in the second month of treatment (41.59%). Modification of the treatment regimen was unnecessary. One patient required concomitant medication to counter the adverse effects. The cure rate was 100%.

CONCLUSIONS

The overall incidence of adverse effects related to the new treatment regimen recommended by the Brazilian Ministry of Health was high. However, none of those effects demanded a change in the regimen, which was effective in the patients evaluated.

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.

A prospective study of hepatitis during antituberculous treatment in Taiwanese patients and a review of the literature

BACKGROUND/PURPOSE

The present study prospectively investigated the incidence of and factors associated with hepatitis during antituberculous treatment in patients with tuberculosis and various underlying diseases. The results were compared with those of previously published studies.

METHODS

Patients treated with antituberculous agents were enrolled from July 1, 2000 to July 31, 2001, in the divisions of chest and infectious diseases at National Taiwan University Hospital and followed until November 30, 2001. Hepatitis was defined as an aminotransferase level>5 times the upper limit of normal (ULN), or >3 times ULN in the presence of symptoms of hepatitis, or total bilirubin level>3 mg/dL. Studies reporting the incidence of hepatitis during antituberculous treatment were reviewed for comparison.

RESULTS

Among 261 patients, median age was 58 years (range, 17-90 years), 17.7% had abnormal baseline liver function tests and 18.4% had concurrent hepatotoxic drug use. Fifteen patients (5.7%) had hepatitis B virus infection, 17 (6.5%) had hepatitis C virus infection, 14 (5.4%) had liver cirrhosis, and 15 (5.7%) had human immunodeficiency virus infection. Hepatitis occurred in 42 patients (16.1%), with 60% of the events in the first 2 months of treatment. Such an incidence was comparable to that in other Asian countries (5.3-18.2%) and slightly higher than that in Western countries (2.4-19%). In multivariate analysis, abnormal liver function tests at baseline and liver cirrhosis were independent factors for development of hepatitis.

CONCLUSION

Elevation of liver function tests was not uncommon during antituberculous treatment, especially in the first 2 months. Patients with abnormal liver function tests at baseline or liver cirrhosis should be closely monitored.

Adverse reactions to first-line antituberculosis drugs

INTRODUCTION

Tuberculosis continues to be a major cause of morbidity and mortality worldwide. Currently available drugs are effective for treatment of the disease or latent infection, but may cause serious adverse effects.

METHODS

The authors reviewed the literature for side effects of five first-line antituberculous medications (isoniazid, rifampin, pyrazinamide, ethambutol and streptomycin). Incidence of the major side effects were compiled with particular attention to the incidence of isoniazid hepatotoxicity.

RESULTS

Hepatotoxicity to isoniazid is a serious problem. Although overall incidence may be decreasing, incidence averaged 9.2 per 1000 patients who were compliant, in multiple studies, with a case fatality rate of 4.7%. The incidence is higher with increasing age. Other serious adverse effects include dermatological, gastrointestinal, hypersensitivity, neurological, haematological and renal reactions. They can lead to drug discontinuation (in up to 10% of patients) or even more serious morbidity or mortality.

CONCLUSIONS

Side effects to antituberculosis drugs are common, and include hepatitis, cutaneous reactions, gastrointestinal intolerance, haematological reactions and renal failure. These adverse effects must be recognised early, to reduce associated morbidity and mortality.

Diagnostic and therapeutic problems of pulmonary tuberculosis in elderly patients

To identify differences in the clinical, radiologic, and microbiologic features of pulmonary tuberculosis (TB) in the young (<64 yr) and elderly (> or =65 yr), we performed a retrospective analysis of the medical charts and chest radiographs of 207 young and 119 elderly pulmonary TB patients. Hemoptysis and a febrile sense were more frequent in the young, whereas weakness, dyspnea, anorexia, and mental change were more frequent in the elderly. Elderly patients showed higher frequencies of cardiovascular and chronic lung diseases, whereas the young showed a higher proportion of underlying liver disease. In addition, chest radiography showed a significantly higher frequency of mid or lower lung involvement by TB lesions in the elderly (10.6% vs. 22.7%, p<0.05). Lesions were frequently misdiagnosed as pneumonia or lung cancer in the elderly. However, there was no difference between these two groups in terms of sputum acid-fast bacilli positivity. The elderly showed a higher frequency of adverse drug reactions (18.5% vs. 40.7%, p<0.05), and higher TB-related mortality (1.3% vs. 11.1%, p<0.05). In conclusion this study showed that young and elderly pulmonary TB patients have similar microbiologic features; however, the elderly showed higher frequencies of atypical clinical and radiologic presentations, adverse drug reactions, and higher TB-related mortality.

Pharmacokinetic and pharmacodynamic factors that can affect sensitivity to neurotoxic sequelae in elderly individuals

Early-life exposure to agents that modulate neurologic function can have long-lasting effects well into the geriatric period. Many other factors can affect neurologic function and susceptibility to neurotoxicants in elderly individuals. In this review we highlight pharmacokinetic and pharmacodynamic factors that may increase geriatric susceptibility to these agents. There is a decreasing trend in hepatic metabolizing capacity with advancing years that can affect the ability to clear therapeutic drugs and environmental chemicals. This factor combined with decreased renal clearance causes prolonged retention of numerous drugs in elderly individuals. A geriatric pharmacokinetic database was developed to analyze changes in drug clearance with advancing age. This analysis shows that the half-life of drugs processed by hepatic cytochrome P450 enzymes or via renal elimination is typically 50-75% longer in those older than 65 than in young adults. Liver and kidney diseases are more common in elderly individuals and can further decrease the clearance function of these organs. Polypharmacy, the administration of numerous drugs to a single patient, is very common in elderly individuals and increases the risks for drug interaction and side effects. With advancing age the nervous system undergoes a variety of changes, including neuronal loss, altered neurotransmitter and receptor levels, and decreased adaptability to changes induced by xenobiotics. These changes in the central nervous system can make elderly individuals more susceptible to neurologic dysfunction when confronted with single pharmacologic agents, polypharmacy, or environmental toxicants. The many factors that affect elderly responses to neuroactive agents make environmental risk assessment for this age group a special concern and present a unique challenge.

Effect of anti-tuberculosis therapy on liver function of pulmonary tuberculosis patients infected with hepatitis B virus

AIM

To observe the effect of anti-tuberculosis therapy on liver function of pulmonary tuberculosis patients with hepatitis B virus (HBV) infection, and to compare the differences of liver function by two treatments of anti-tuberculosis.

METHODS

Forty-seven TB patients with HBV infection and 170 TB patients without HBV infection were divided into HPBE(S) and HLAMKO treatment groups. Liver function tests before and after the treatments were performed once in 2 wk or monthly, and their clinical manifestations were recorded.

RESULTS

The rate of hepatotoxicity occurred in 26 (59%) TB patients with HBV during anti-TB treatment, higher than that in 40 (24%) TB patients without HBV. Hepatotoxicity occurred in 66 out of 217 patients, and the incidence of liver dysfunction was 46.1% in HPBE(S) group, significantly higher than that in HLAMKO group (12.7%) (P<0.01).

CONCLUSION

TB patients with HBV should choose HLAMKO treatment because of fewer hepatotoxicity.

Tuberculosis prevention and control in long-term-care facilities for older adults

In the United States, older adults comprise 22% of cases of tuberculous disease but only 12% of the population. Most cases of tuberculosis (TB) occur in community dwellers, but attack rates are highest among frail residents of long-term-care facilities. The detection and treatment of latent TB infection and TB disease can pose special challenges in older adults. Rapid recognition of possible disease, diagnosis, and implementation of airborne precautions are essential to prevent spread. It is the intent of this evidence-based guideline to assist healthcare providers in the prevention and control of TB, specifically in skilled nursing facilities for the elderly.

Unique aspects of antimicrobial use in older adults

Elderly persons consume a significant proportion of health care resources. Antimicrobials are just one class among many pharmaceuticals that are prescribed more frequently to elderly patients than to younger patients. There are unique aspects of antimicrobial use in elderly persons that make prescribing complicated and monitoring unpredictable. Physiologic changes associated with aging result in altered pharmacokinetics, and accurate estimates of renal function cannot be made with standard methods. Together, these qualities make antimicrobial dosing difficult. Because of a higher prevalence of other chronic diseases, there is a greater propensity for polypharmacy and a resulting risk of an adverse event or a significant drug interaction. Lastly, irrespective of altered pharmacokinetics, adverse effects of many antimicrobials are more common in elderly persons, which introduces an added dimension to ensuring safety with antimicrobial therapy.

Revised Guidelines for the Diagnosis and Control of Tuberculosis

Despite major progress in the development of new strategies for diagnosing and treating tuberculosis, the disease still remains a major challenge for healthcare workers throughout the world. A number of causes are responsible for this threat but, unfortunately, many of these cannot be resolved easily because of cultural and social factors. Furthermore, not all countries throughout the world have enough financial resources to support educational and therapeutic programmes. The major challenges with tuberculosis are 2-fold: (i) to deal with the growing epidemic around the world (and especially in 'low-income' [developing] countries), and; (ii) to ensure correct use of antituberculosis medications in order to protect these drugs for future use. In 'high-income' countries, a major decline in the incidence of tuberculosis has been observed. Nevertheless, tuberculosis remains an important challenge in some risk groups, particularly the elderly patient, in these countries. The clinical and radiological presentations are often nonspecific, leading to delayed diagnosis and appropriate treatment, which often results in a large proportion of cases being discovered at autopsy only. Considering tuberculosis in the differential diagnosis remains the cornerstone of a fast and accurate diagnosis of this condition. Management of active tuberculosis in the elderly does not differ fundamentally from that in younger patients with respect to outcomes or adverse effects of treatment. However, empirical treatment perhaps may be considered more readily in the elderly patient. Elderly persons infected with tuberculosis at the beginning of the 20th century constitute a large reservoir of latent tuberculosis infection. Furthermore, these individuals are at increased risk of reactivation of this remote infection as their immunological status declines with aging. Compared with the past, modern guidelines are less reluctant to recommend use of tuberculin skin testing, treatment of latent tuberculosis infection in elderly persons, and prevention of transmission of tuberculosis in nursing homes.

Hepatotoxicity of Rifampin and Pyrazinamide in the Treatment of Latent Tuberculosis Infection in HIV-Infected Persons: Is It Different Than in HIV-Uninfected Persons?

BACKGROUND

In 2000, results of a multinational trial demonstrated that a 2-month course of rifampin and pyrazinamide (RZ) was as effective as isoniazid (INH) in reducing tuberculosis in human immunodeficiency virus (HIV)-infected individuals with latent tuberculosis infection (LTBI). After the release of new guidelines, the Centers for Disease Control and Prevention received reports of severe hepatotoxicity associated with the use of the RZ regimen for the treatment of LTBI in the general population. To better understand the occurrence of hepatotoxicity in an HIV-infected population, we conducted a more detailed analysis of the liver function test results obtained in the multinational trial of RZ.

METHODS

At study entry, patients were required to have a bilirubin level of < or =2.5 mg/dL and both an aspartate aminotransferase (AST) level and an alkaline phosphatase level of < or =5 times the upper limit of normal. Patients with acute hepatitis were excluded. At months 1 and 2 of the study, all patients had bilirubin and AST levels measured.

RESULTS

There was no difference between the RZ and INH groups with regard to AST level or bilirubin level at baseline. An increase in the AST level of > or =40 U/L was associated with the use of INH and older age; and an increase in the bilirubin level of > or =0.5 mg/dL was associated with the use of RZ, male sex, and nonwhite race (P<.05). An absolute AST level of >250 U/L occurred in 12 of 745 INH recipients and in 15 of 721 RZ recipients (P=.56), and an absolute bilirubin level of >2.5 mg/dL occurred in 5 of 743 INH recipients and 13 of 718 RZ recipients (P=.06).

CONCLUSIONS

These data demonstrate very little liver injury associated with either INH or RZ in the HIV-infected subjects, leaving unclear the reasons for serious RZ-related liver damage in the general population.

Tolerance of aged Fischer 344 rats against chlordecone-amplified carbon tetrachloride toxicity

We have investigated the effects of chlordecone 1(CD)+CCl4 combination in adult (3 months), middle aged (14 months), and old aged (24 months) male Fischer 344 (F344) rats. After a non-toxic dietary regimen of CD (10 ppm) or normal powdered diet for 15 days, rats received a single non-toxic dose of CCl4 (100 microl/kg, i.p., 1:4 in corn oil) or corn oil (500 microl/kg, i.p.) alone on day 16. Liver injury was assessed by plasma ALT, AST, and histopathology during a time course of 0-96 h. Liver tissue repair was measured by [3H-CH3]-thymidine (3H-T) incorporation into hepatic nuclear DNA and proliferating cell nuclear antigen (PCNA) immunohistochemistry. Hepatomicrosomal CYP2E1 protein, enzyme activity, and covalent binding of 14CCl4-derived radiolabel were measured in normal and CD fed rats. Exposure to CCl4 alone caused modest liver injury only in 14- and 24-month-old rats but neither progression of injury nor mortality. The CD+CCl4 combination led to 100% mortality in 3-month-old rats by 72 h, whereas none of the 14- and 24-month-old rats died. Both 3- and 14-month-old rats exposed to CD+Cl4 had identical liver injury up to 36 h indicating that bioactivation-mediated CCl4 injury was the same in the two age groups. Thereafter, liver injury escalated only in 3-month-old while it declined in 14-month-old rats. In 24-month-old rats initial liver injury at 6 h was similar to the 3- and 14-month-old rats and thereafter did not develop to the level of the other two age groups, recovering from injury by 96 h as in the 14-month-old rats. Neither hepatomicrosomal CYP2E1 protein nor the associated p-nitrophenol hydroxylase activity or covalent binding of 14CCl4-derived radiolabel to liver tissue differed between the age groups or diet regimens 2 h after the administration of 14CCl4. Compensatory liver tissue repair (3H-T, PCNA) was prompt and robust soon after CCl4 liver injury in the 14- and 24-month-old rats. In stark contrast, in the 3-month-old rats it failed allowing unabated progression of liver injury. These findings suggest that stimulation of early onset and robust liver tissue repair rescue the 14- and 24-month-old F344 rats from the lethal effect of the CD+CCl4 combination.

Incidence of serious side effects from first-line antituberculosis drugs among patients treated for active tuberculosis

Major adverse reactions to antituberculosis drugs can cause significant morbidity, and compromise treatment regimens for tuberculosis (TB). Among patients treated for active TB we estimated the incidence, and risk factors, of major side effects from first-line anti-TB drugs. Side effects, resulting in modification or discontinuation of therapy, or hospitalization, were attributed on the basis of resolution after withdrawal, and/or recurrence with rechallenge. Among 430 patients treated between 1990 and 1999, the incidence of all major adverse effects was 1.48 per 100 person-months of exposure (95% confidence interval [95% CI], 1.31 to 1.61) for pyrazinamide, compared with 0.49 (95% CI, 0.42 to 0.55) for isoniazid, 0.43 (95% CI, 0.37 to 0.49) for rifampin, and 0.07 (95% CI, 0.04 to 0.10) for ethambutol. Occurrence of any major side effect was associated with female sex (adjusted hazard ratio, 2.5; 95% CI, 1.3 to 4.7), age over 60 years (adjusted hazard ratio, 2.9; 95% CI, 1.3 to 6.3), birthplace in Asia (adjusted hazard ratio, 2.5; 95% CI, 1.3 to 5.0), and human immunodeficiency virus-positive status (adjusted hazard ratio, 3.8; 95% CI, 1.05 to 13.4). Pyrazinamide-associated adverse events were associated with age over 60 years (adjusted hazard ratio, 2.6; 95% CI, 1.01 to 6.6) and birthplace in Asia (adjusted hazard ratio, 3.4; 95% CI, 1.4 to 8.3), whereas rifampin-associated adverse events were associated with age over 60 years (adjusted hazard ratio, 3.9; 95% CI, 1.02 to 14.9) and human immunodeficiency virus-positive status (adjusted hazard ratio, 8.0; 95% CI, 1.5 to 43). The incidence of pyrazinamide-induced hepatotoxicity and rash during treatment for active TB was substantially higher than with the other first-line anti-TB drugs, and higher than previously recognized.

Safety of 2 months of rifampin and pyrazinamide for treatment of latent tuberculosis

An alternative regimen for the treatment of latent tuberculosis infection is 2 months of rifampin and pyrazinamide, but some patients have died of hepatitis associated with this therapy. One hundred fourteen patients received rifampin/pyrazinamide in Wake County, North Carolina, between December 1999 and May 2002; 60.5% of these patients were homeless, and at least 17% drank alcohol to excess. Seventy-seven patients (67.5%) completed a full 2-month course. Nine patients had a history of viral hepatitis or chronic liver disease. Four of 114 (3.5%; 95% confidence interval, 1.0-8.7%) patients developed hepatitis on therapy, and another two had symptoms consistent with hepatitis but did not report for laboratory testing (total confirmed plus suspected hepatitis rate 5.3%; 95% confidence interval, 2.0-11.1%). No patient who developed hepatitis had a history of viral hepatitis or liver disease, and none had been previously treated with isoniazid. No patients died or were hospitalized due to drug side effects. Rifampin/pyrazinamide was associated with a significantly higher rate of hepatitis than previously described with isoniazid therapy for latent tuberculosis but resulted in a high completion rate. The rifampin/pyrazinamide regimen for latent tuberculosis infection may be useful for high-risk, traditionally nonadherent patient groups, but careful monitoring for toxicity is required.

Tuberculosis in the elderly

As the result of the strengthening of TB-control programs nationwide, a decline in the overall number of reported TB cases in the United States has been observed within the last 10 years. Despite these declines in absolute numbers, the elderly continue to account for a disproportionate share of the cases. The high number of cases diagnosed at autopsy among the elderly suggests that this condition often remains unrecognized, possibly due to the subtle clinical manifestations in this age group. Evidence suggests that, compared with their community-dwelling counterparts, the institutionalized elderly are at a greater risk for re-activation of latent TB and for the acquisition of new TB infection. More studies are needed to make final conclusions. New guidelines for the treatment of LTBI emphasize targeted TST among persons at high risk for development of active TB and no longer use age as an exclusionary condition. All nursing home residents must therefore be regularly screened for LTBI and treated if necessary. Even though elderly persons are at greater risk for hepatic toxicity from TB treatment, the poor outcome of untreated TB in this age group warrants more aggressive treatment of this condition.

Ageing and infection

Average life expectancy throughout developed countries has rapidly increased during the latter half of the 20th century and geriatric infectious diseases have become an increasingly important issue. Infections in the elderly are not only more frequent and more severe, but they also have distinct features with respect to clinical presentation, laboratory results, microbial epidemiology, treatment, and infection control. Reasons for increased susceptibility include epidemiological elements, immunosenescence, and malnutrition, as well as a large number of age-associated physiological and anatomical alterations. Moreover, ageing may be the cause of infection but infection can also be the cause of ageing. Mechanisms may include enhanced inflammation, pathogen-dependent tissue destruction, or accelerated cellular ageing through increased turnover. In most instances, treatment of infection leads to a satisfactory outcome in the elderly. However, in palliative care situations and in patients with terminal dementia, the decision whether or not to treat an infectious disease is becoming a difficult ethical issue.

Age-related susceptibility to hepatotoxicants

Limited information is available regarding age-associated events that lead to differences in vulnerability to chemicals that injure the liver. For some agents, such as allyl alcohol, alterations in metabolic activation, by liver biotransformation enzymes, are responsible for age-associated changes in severity of liver damage. For other toxicants, such as carbon tetrachloride, there appears to be no relation between changes in activation/detoxification processes and the effects of aging on the extent of liver injury. With diquat, a rise in iron content seems to explain the increased toxicity observed in hepatocytes of old rats compared with those of young-adult rats. Additional research is needed to identify the mechanisms responsible for age-dependent differences in sensitivity to environmental chemicals.

Therapeutic efficacies of isoniazid and rifampin encapsulated in lung-specific stealth liposomes against Mycobacterium tuberculosis infection induced in mice

One recent promising development in the modification of drug formulations to improve chemotherapy is the use of a liposome-mediated drug delivery system. The efficacies of isoniazid and rifampin encapsulated in lung-specific stealth liposomes were evaluated by injecting liposomal drugs and free drugs into tuberculous mice twice a week for 6 weeks. Liposome-encapsulated drugs at and below therapeutic concentrations were more effective than free drugs against tuberculosis, as evaluated on the basis of CFUs detected, organomegaly, and histopathology. Furthermore, liposomal drugs had marginal hepatotoxicities as determined from the levels of total bilirubin and hepatic enzymes in serum. The elimination of mycobacteria from the liver and spleen was also higher with liposomal drugs than with free drugs. The encapsulation of antitubercular drugs in lung-specific stealth liposomes seems to be a promising therapeutic approach for the chemotherapy of tuberculosis.