Long-term tolerance and effectiveness of moxifloxacin therapy for tuberculosis: preliminary results

Current Status of Fluoroquinolone Use for Treatment of Tuberculosis in a Tertiary Care Hospital in Korea

Background

Fluoroquinolones are considered important substitutes for the treatment of tuberculosis. This study investigates the current status of fluoroquinolone for the treatment of tuberculosis.

Methods

In 2009, a retrospective analysis was performed at one tertiary referral center for 953 patients diagnosed with tuberculosis.

Results

A total of 226 patients (23.6%), who received fluoroquinolone at any time during treatment for tuberculosis, were enrolled in this study. The most common reasons for fluoroquinolone use were adverse events due to other anti-tuberculosis drugs (52.7%), drug resistance (23.5%), and underlying diseases (16.8%). Moxifloxacin (54.0%, 122/226) was the most commonly administered fluoroquinolone, followed by levofloxacin (36.3%, 82/226) and ofloxacin (9.7%, 22/226). The frequency of total adverse events from fluoroquinolone-containing anti-tuberculosis medication was 22.6%, whereas fluoroquinolone-related adverse events were estimated to be 2.2% (5/226). The most common fluoroquinolone-related adverse events were gastrointestinal problems (3.5%, 8/226). There were no significant differences in the treatment success rate between the fluoroquinolone and fluoroquinolone-naïve groups (78.3% vs. 78.4%, respectively).

Conclusion

At our institution, fluoroquinolones are commonly used for the treatment of both multidrug-resistant tuberculosis and susceptible tuberculosis, especially as a substitute for adverse event-related drugs. Considering the low adverse event rates and the comparable treatment success rates, fluoroquinolones seem to be an invaluable drug for the treatment of tuberculosis.

Gender analysis of moxifloxacin clinical trials

PURPOSE

To determine the inclusion of women and the sex-stratification of results in moxifloxacin Clinical Trials (CTs), and to establish whether these CTs considered issues that specifically affect women, such as pregnancy and use of hormonal therapies. Previous publications about women's inclusion in CTs have not specifically studied therapeutic drugs. Although this type of drug is taken by men and women at a similar rate, adverse effects occur more frequently in the latter.

METHODS

We reviewed 158 published moxifloxacin trials on humans, retrieved from MedLine and the Cochrane Library (1998-2010), to determine whether they complied with the gender recommendations published by U.S. Food and Drug Administration Guideline.

RESULTS

Of a total of 80,417 subjects included in the moxifloxacin CTs, only 33.7% were women in phase I, in contrast to phase II, where women accounted for 45%, phase III, where they represented 38.3% and phase IV, where 51.3% were women. About 40.9% (n=52) of trials were stratified by sex and 15.3% (n=13) and 9% (n=7) provided data by sex on efficacy and adverse effects, respectively. We found little information about the influence of issues that specifically affect women. Only 3 of the 59 journals that published the moxifloxacin CTs stated that authors should stratify their results by sex.

CONCLUSIONS

Women are under-represented in the published moxifloxacin trials, and this trend is more marked in phase I, as they comprise a higher proportion in the other phases. Data by sex on efficacy and adverse effects are scarce in moxifloxacin trials. These facts, together with the lack of data on women-specific issues, suggest that the therapeutic drug moxifloxacin is only a partially evidence-based medicine.

Fluoroquinolones for treating tuberculosis (presumed drug-sensitive)

BACKGROUND

Currently the World Health Organization only recommend fluoroquinolones for people with presumed drug-sensitive tuberculosis (TB) who cannot take standard first-line drugs. However, use of fluoroquinolones could shorten the length of treatment and improve other outcomes in these people. This review summarises the effects of fluoroquinolones in first-line regimens in people with presumed drug-sensitive TB.

OBJECTIVES

To assess fluoroquinolones as substitute or additional components in antituberculous drug regimens for drug-sensitive TB.

SEARCH METHODS

We searched the Cochrane Infectious Diseases Group Specialized Register; CENTRAL (The Cochrane Library 2013, Issue 1); MEDLINE; EMBASE; LILACS; Science Citation Index; Databases of Russian Publications; and metaRegister of Controlled Trials up to 6 March 2013.

SELECTION CRITERIA

Randomized controlled trials (RCTs) of antituberculous regimens based on rifampicin and pyrazinamide and containing fluoroquinolones in people with presumed drug-sensitive pulmonary TB.

DATA COLLECTION AND ANALYSIS

Two authors independently applied inclusion criteria, assessed the risk of bias in the trials, and extracted data. We used the risk ratio (RR) for dichotomous data and the fixed-effect model when it was appropriate to combine data and no heterogeneity was present. We assessed the quality of evidence using the GRADE approach.

MAIN RESULTS

We identified five RCTs (1330 participants) that met the inclusion criteria. None of the included trials examined regimens of less than six months duration. Fluoroquinolones added to standard regimensA single trial (174 participants) added levofloxacin to the standard first-line regimen. Relapse and treatment failure were not reported. For death, sputum conversion, and adverse events we are uncertain if there is an effect (one trial, 174 participants, very low quality evidence for all three outcomes). Fluoroquinolones substituted for ethambutol in standard regimens Three trials (723 participants) substituted ethambutol with moxifloxacin, gatifloxacin, and ofloxacin into the standard first-line regimen. For relapse, we are uncertain if there is an effect (one trial, 170 participants, very low quality evidence). No trials reported on treatment failure. For death, sputum culture conversion at eight weeks, or serious adverse events we do not know if there was an effect (three trials, 723 participants, very low quality evidence for all three outcomes). Fluoroquinolones substituted for isoniazid in standard regimens A single trial (433 participants) substituted moxifloxacin for isoniazid. Treatment failure and relapse were not reported. For death, sputum culture conversion, or serious adverse events the substitution may have little or no difference (one trial, 433 participants, low quality evidence for all three outcomes). Fluoroquinolines in four month regimensSix trials are currently in progress testing shorter regimens with fluoroquinolones.

AUTHORS' CONCLUSIONS

Ofloxacin, levofloxacin, moxifloxacin, and gatifloxacin have been tested in RCTs of standard first-line regimens based on rifampicin and pyrazinamide for treating drug-sensitive TB. There is insufficient evidence to be clear whether addition or substitution of fluoroquinolones for ethambutol or isoniazid in the first-line regimen reduces death or relapse, or increases culture conversion at eight weeks. Much larger trials with fluoroquinolones in short course regimens of four months are currently in progress.

New regimens for reducing the duration of the treatment of drug-susceptible pulmonary tuberculosis

Tuberculosis (TB) remains an important health problem worlwide. The structure necessary for delivering TB treatment and implementing the directly observed treatment accounts for more than two-thirds of its final cost. Furthemore, although with efficacy greater than 90%, the effectiveness of present treatment regimens ranges from 55-85%, depending on the setting, mainly due to poor adherence. Duration of treatment with the current first-line anti-TB drugs is a minimum of 6 months. Reducing the duration of the treatment from six to two months or less could result in significant increase of adherence to treatment and cost reduction. The aim of this review is to highlight potential new agents or new drug combinations that could reduce the time of treatment of drug-susceptible TB, currently under study or recently evaluated through clinical trials. We conducted a literature search in the English language for clinical studies as well as an electronic computer-assisted and manual search. The literature search was conducted on November 2010, using MEDLINE (2000-2010), EMBASE (2000-2010) and the National Institute of Health (NIH) Clinical Trials Register database (2000-2010). Most of the new agents identified as anti-TB drug candidates are still in the preclinical phases. Nitroimidazole-PA-824 and fluoroquinolones are evaluated while two first line drugs - rifampicin and rifapentine -are re-evaluated to optimize their efficacy in new ultra-short anti-TB regimens through phases II/III clinical studies. A summary of the studies are presented, with their potential to change recommendations for TB treatment in the near future.

New antituberculous drugs in development

There have been no new antituberculous drugs since the introduction of rifampin in 1952. The collision of the HIV and tuberculosis (TB) epidemics in developing regions of the world together with the emergence of multidrug resistance and extensively drug-resistant strains of TB has emphasized the urgent need for newer antituberculous drugs. There is a need for drugs that are safe, effective against resistant strains, are able to shorten the course of treatment, are effective for latent TB infection, and that have minimal interactions with antiretroviral drugs. Drugs that are currently in phase 3 development are moxifloxacin and gatifloxacin. In phase 2 development are PA-824 and TMC207; and in phase 1 are SQ109, AZD5847, and linezolid. Nanotechnology holds future promise for targeted drug delivery. Immunotherapy such as new vaccines and vitamin D may serve as adjunctive treatment for prevention and active disease, together with shortening the course of treatment. Bringing newer and more effective antituberculous drugs to market is a global priority and the process must be accelerated.

Acute liver failure due to antitubercular therapy: Strategy for antitubercular treatment before and after liver transplantation

The standard antitubercular treatment (ATT), which consists of isoniazid (INH), rifampicin (RIF), ethambutol, and pyrazinamide (PZA), is the best available treatment for tuberculosis (TB). However, the hepatotoxicity of INH and PZA can be severe, and even after drug withdrawal, patients may require liver transplantation (LT). In these cases, the strategy for the treatment of TB is poorly defined. Between 1986 and 2008, 14 patients presented at our department with severe hepatitis secondary to INH and PZA treatment. Four of these patients were immunosuppressed: 2 after renal transplantation and 2 because of human immunodeficiency virus infection. In seven of the 14 patients an alternative ATT was begun on admission, which was well tolerated. Hepatitis improved spontaneously in 5 patients, and alternative ATT was continued for 9.3 ± 4.2 months; 1 patient deteriorated and underwent LT, and 1 patient died. ATT was stopped definitively in 2 patients. Six patients required urgent LT, and alternative ATT was started after transplantation and was successful. Five patients receiving RIF had an episode of acute rejection. In conclusion, hepatitis secondary to ATT can be successfully treated with alternative anti-TB regimens. The use of RIF in LT patients may lead to acute rejection. RIF should therefore be avoided in these patients.

[Use of moxifloxacin in tuberculosis regimen in a French teaching hospital]

OBJECTIVE

To evaluate retrospectively indications of moxifloxacin prescriptions in inpatients with tuberculosis in a referent teaching hospital.

DESIGN

All patients hospitalized at Bichat-Claude Bernard hospital and who had an active tuberculosis disease with a tuberculosis regimen including moxifloxacin were included. Medical charts were retrospectively reviewed for all these patients over 21 months. Data collected were reasons for introduction of moxifloxacin in regimen.

RESULTS

Out of the 23 patients included in the study, 13 of them had a recurrence of tuberculosis. Several reasons for introduction of moxifloxacin were recorded and one prescription can be associated with one or more reasons: an extra pulmonary tuberculosis or disseminated tuberculosis (16 cases), an intolerance to other anti-tuberculosis drugs (13 cases), a medical history of therapeutic failure or a proved or suspected drug-resistant Mycobacterium tuberculosis (12 cases) or to avoid drug interactions (two cases).

CONCLUSIONS

This retrospective study in our hospital highlights that drug-resistance was not the first reason for introduction of moxifloxacin in anti-tuberculosis regimen. One major indication was bad tolerance to other first-line regimen drugs. A better supervision of the moxifloxacin prescription in tuberculosis regimen is needed in order to limit its ecological impact.

Management of multidrug-resistant tuberculosis: Update 2007

Multidrug-resistant tuberculosis (MDR-TB) with bacillary resistance to at least isoniazid and rifampicin in vitro is a worldwide phenomenon. Hot spots of the disease are found scattered in different continents. Prevention of its development through good tuberculosis control programmes operating under the directly observed therapy, short-course (DOTS) strategy is of paramount importance. However, with established MDR-TB, treatment with alternative and specific chemotherapy is necessary to achieve a beneficial outcome. Such an approach on a programme basis is currently known as the 'DOTS-Plus' strategy. Second-line (reserve) drugs utilized in the treatment of MDR-TB are generally less potent and more toxic, perhaps with the notable exceptions of some fluoroquinolones and injectable agents. Surgery has a distinct adjunctive role for the management of MDR-TB in selected patients. The emergence of extensively drug-resistant tuberculosis (XDR-TB), that is, MDR-TB with additional bacillary resistance to the fluoroquinolones and injectables, has provided a very alarming challenge to global health, as the disease currently has a low cure rate and high mortality. In order to combat XDR-TB, strengthening of DOTS and DOTS-Plus programmes is mandatory, especially in the face of surging HIV infection. Furthermore, more attention needs to be focused on developing new drugs with potent bactericidal and sterilizing activities and low side-effects, and above all, drugs that are affordable for communities worldwide.

Fluoroquinolones for treating tuberculosis

BACKGROUND

Fluoroquinolones are sometimes used to treat multiple-drug-resistant and drug-sensitive tuberculosis. The effects of fluoroquinolones in tuberculosis regimens need to be assessed.

OBJECTIVES

To assess fluoroquinolones as additional or substitute components to antituberculous drug regimens for drug-sensitive and drug-resistant tuberculosis.

SEARCH STRATEGY

In July 2007, we searched the Cochrane Infectious Diseases Group Specialized Register, CENTRAL (The Cochrane Library 2007, Issue 3), MEDLINE, EMBASE, LILACS, Science Citation Index, Database of Russian Publications, and metaRegister of Controlled Trials. We also scanned reference lists of all identified studies and contacted researchers.

SELECTION CRITERIA

Randomized controlled trials of antituberculous regimens containing fluoroquinolones in people diagnosed with bacteriologically positive (sputum smear or culture) pulmonary tuberculosis.

DATA COLLECTION AND ANALYSIS

Two authors independently applied inclusion criteria, assessed methodological quality, and extracted data. We used relative risk (RR) for dichotomous data, weighted mean difference (WMD) for continuous data (both with 95% confidence intervals (CI)), and the random-effects model if we detected heterogeneity and it was appropriate to combine data.

MAIN RESULTS

Eleven trials (1514 participants) met the inclusion criteria. No statistically significant difference was found in trials substituting ciprofloxacin, ofloxacin or moxifloxacin for first-line drugs in relation to cure (416 participants, 3 trials), treatment failure (388 participants, 3 trials), or clinical or radiological improvement (216 participants, 2 trials). Substituting ciprofloxacin into first-line regimens in drug-sensitive tuberculosis led to a higher incidence of relapse (RR 7.17, 95% CI 1.33 to 38.58; 384 participants, 3 trials) and longer time to sputum culture conversion (WMD 0.50 months, 95% CI 0.18 to 0.82; 168 participants, 1 trial), although this was confined to HIV-positive participants. Substituting for ethambutol in first-line regimens led to a higher incidence of total number of adverse events (RR 1.34, 95% CI 1.05 to 1.72; 492 participants, 2 trials). Adding or substituting levofloxacin to basic regimens in drug-resistant areas had no effect. A comparison of sparfloxacin versus ofloxacin added to regimens showed no statistically significant difference in cure (184 participants, 2 trials), treatment failure (149 participants, 2 trials), or the total number of adverse events (253 participants, 3 trials).

AUTHORS' CONCLUSIONS

Only ciprofloxacin, ofloxacin, levofloxacin, sparfloxacin and moxifloxacin have been tested in randomized controlled trials for treating tuberculosis. We cannot recommend ciprofloxacin in treating tuberculosis. Trials of newer fluoroquinolones for treating tuberculosis are needed and are on-going. No difference has been demonstrated between sparfloxacin and ofloxacin in drug-resistant tuberculosis.

Daily dosing of rifapentine cures tuberculosis in three months or less in the murine model

BACKGROUND

Availability of an ultra-short-course drug regimen capable of curing patients with tuberculosis in 2 to 3 mo would significantly improve global control efforts. Because immediate prospects for novel treatment-shortening drugs remain uncertain, we examined whether better use of existing drugs could shorten the duration of treatment. Rifapentine is a long-lived rifamycin derivative currently recommended only in once-weekly continuation-phase regimens. Moxifloxacin is an 8-methoxyfluoroquinolone currently used in second-line regimens.

METHODS AND FINDINGS

Using a well-established mouse model with a high bacterial burden and human-equivalent drug dosing, we compared the efficacy of rifapentine- and moxifloxacin-containing regimens with that of the standard daily short-course regimen based on rifampin, isoniazid, and pyrazinamide. Bactericidal activity was assessed by lung colony-forming unit counts, and sterilizing activity was assessed by the proportion of mice with culture-positive relapse after 2, 3, 4, and 6 mo of treatment. Here, we demonstrate that replacing rifampin with rifapentine and isoniazid with moxifloxacin dramatically increased the activity of the standard daily regimen. After just 2 mo of treatment, mice receiving rifapentine- and moxifloxacin-containing regimens were found to have negative lung cultures, while those given the standard regimen still harbored 3.17 log10 colony-forming units in the lungs (p < 0.01). No relapse was observed after just 3 mo of treatment with daily and thrice-weekly administered rifapentine- and moxifloxacin-containing regimens, whereas the standard daily regimen required 6 mo to prevent relapse in all mice.

CONCLUSIONS

Rifapentine should no longer be viewed solely as a rifamycin for once-weekly administration. Our results suggest that treatment regimens based on daily and thrice-weekly administration of rifapentine and moxifloxacin may permit shortening the current 6 mo duration of treatment to 3 mo or less. Such regimens warrant urgent clinical investigation.

Infections caused by mycobacterium tuberculosis in patients with hematological disorders and in recipients of hematopoietic stem cell transplant, a twelve year retrospective study

BACKGROUND

Tuberculous infections in patients with hematological disorders and hematopoietic stem cell transplant vary in incidence, complications and response to treatment.

METHODS AND MATERIALS

A retrospective study of patients with various benign and malignant hematological disorders and recipients of hematopoietic stem cell transplant who were treated at Riyadh Armed Forces Hospital, Saudi Arabia between January 1991 and December 2002 and who developed tuberculous infections was conducted.

RESULTS

Tuberculous infections occurred in eighteen patients with hematological disorders and hematopoietic stem cell transplant. The main associated factors were: reduced immunity due to the primary hematological disorder, age more than 50 years and the administration of cytotoxic chemotherapy, steroids or radiotherapy. These infections frequently involved the lungs and predominantly occurred in males and in patients with chronic myeloproliferative disorders, myelodysplastic syndrome and acute myeloid leukemia. In patients treated with intravenous cytotoxic chemotherapy, tuberculous infections tended to occur earlier and also tended to be more disseminated compared to infections occurring in patients treated with oral chemotherapy. Anti-tuberculous treatment was given to 16 patients and it was successful in 15 of these patients.

CONCLUSION

Tuberculous infections cause significant morbidity and mortality in patients with various hematological disorders and in recipients of hematopoietic stem cell transplant. The early administration of anti-tuberculous therapy and compliance with drug treatment are associated with successful outcomes while delayed management, drug resistance and the presence of miliary infections are associated with poor prognosis and high mortality rates.

Long-term moxifloxacin in complicated tuberculosis patients with adverse reactions or resistance to first line drugs

STUDY OBJECTIVES

To test safety and tolerability of long-term moxifloxacin in resistant tuberculosis (TB) patients and patients with intolerance to first line anti-TB drugs.

DESIGN

Clinical evaluation of adverse events (AEs) during prolonged moxifloxacin treatment.

SETTING

TB Unit of the Regional TB Reference Center, Villa Marelli Institute, Niguarda Ca'Granda Hospital, Milan, Italy

PATIENTS AND INTERVENTIONS

Patients treated with moxifloxacin, 400 mg orally once daily for TB in the Villa Marelli Institute from January 2001 to December 2003 were enrolled.

RESULTS

Thirty-eight patients were treated with moxifloxacin at the Villa Marelli Institute in the study period, for multidrug resistant (MDR) TB (14, 36.8%), for intolerance to first line anti-TB drugs (9, 23.7%), for combined resistance and intolerance to first line anti-TB drugs (12, 31.6%), other reasons (3, 7.9%). The mean duration of moxifloxacin treatment was 6.3 +/- 5.2 months. Twelve (31.6%) patients reported at least an AE due to moxifloxacin, mostly gastrointestinal (8, 21.0%), general (5, 13.2%) and central nervous system (3, 7.9%) AEs. In 4 (10.5%) patients the drug was withdrawn for major AEs; no irreversible or fatal events were recorded. Most of the patients (31, 81.6%) reported a treatment success, even if the success rate was lower in MDR TB patients (8/14, 51.7%).

CONCLUSIONS

Despite the fact that a large proportion of patients experienced at least an AE due to moxifloxacin, the drug resulted safe in the long-term administration for complicated TB cases.

Recent advances in the medical and surgical treatment of multi-drug resistant tuberculosis

PURPOSE OF REVIEW

Multi-drug resistant tuberculosis is a serious clinical problem. Extension of drug resistance to second-line anti-tuberculosis drugs in the form of the W-strain is cause for alarm. There is an urgent need for more rapid recognition of multi-drug resistant tuberculosis and newer therapeutic agents. This review summarizes the recent advances in the diagnosis and treatment of multi-drug resistant tuberculosis including surgery and new developments.

RECENT FINDINGS

Multidrug resistant tuberculosis therapy is characterized by prolonged treatment, high morbidity and mortality, and high relapse rates. New diagnostic procedures that include electrophoretic and molecular hybridization techniques will allow rapid diagnosis. Several new drugs are currently in various phases of development. Moxifloxacin, a respiratory fluoroquinolone, is currently in phase III clinical development. New classes of drugs such as nitroimidazopyrans (PA-824) and diarylquinolines (R-207910) are exciting based on phase I and II data. Immunomodulation with vaccines and interferon-gamma have been unhelpful. Surgery is reserved for selected cases only. Cure rates of over 90% with reasonable morbidity and mortality has been achieved with meticulous preoperative preparation, patient selection and careful surgical technique.

SUMMARY

Newer drugs and defined indications for surgery should provide improved cure rates, with reduced duration of treatment for multi-drug resistant tuberculosis.

Moxifloxacin versus ethambutol in the first 2 months of treatment for pulmonary tuberculosis

RATIONALE

Moxifloxacin has promising preclinical activity against Mycobacterium tuberculosis, but has not been evaluated in multidrug treatment of tuberculosis in humans.

OBJECTIVE

To compare the impact of moxifloxacin versus ethambutol, both in combination with isoniazid, rifampin, and pyrazinamide, on sputum culture conversion at 2 mo as a measure of the potential sterilizing activity of alternate induction regimens.

METHODS

Adults with smear-positive pulmonary tuberculosis were randomized in a factorial design to receive moxifloxacin (400 mg) versus ethambutol given 5 d/wk versus 3 d/wk (after 2 wk of daily therapy). All doses were directly observed.

MEASUREMENTS

The primary endpoint was sputum culture status at 2 mo of treatment.

RESULTS

Of 336 patients enrolled, 277 (82%) were eligible for the efficacy analysis, 186 (67%) were male, 175 (63%) were enrolled at African sites, 206 (74%) had cavitation on chest radiograph, and 60 (22%) had HIV infection. Two-month cultures were negative in 71% of patients (99 of 139) treated with moxifloxacin versus 71% (98 of 138) treated with ethambutol (p = 0.97). Patients receiving moxifloxacin, however, more often had negative cultures after 4 wk of treatment. Patients treated with moxifloxacin more often reported nausea (22 vs. 9%, p = 0.002), but similar proportions completed study treatment (88 vs. 89%). Dosing frequency had little effect on 2-mo culture status or tolerability of therapy.

CONCLUSIONS

The addition of moxifloxacin to isoniazid, rifampin, and pyrazinamide did not affect 2-mo sputum culture status but did show increased activity at earlier time points.

Stepwise Decrease in Moxifloxacin Susceptibility amongst Clinical Isolates of Multidrug-ResistantMycobacterium tuberculosis:Correlation with Ofloxacin Susceptibility

To study the effectiveness of moxifloxacin (MOX) against multidrug-resistant (MDR) Mycobacterium tuberculosis (MTB), in vitro drug susceptibility tests on MOX and ofloxacin (OFX) using the MGIT system against 132 nonduplicate MDR MTB isolates (108 OFX-sensitive and 24 OFX-resistant) were performed. Eleven OFX-resistant non-MDR MTB isolates were also included. All strains that were susceptible to OFX were shown to be also susceptible to MOX. For OFX-resistant isolates, regardless of their MDR status, a 4- to 8-fold decrease in MIC was observed for MOX when compared to OFX. On the basis of similarities in mode of action and pharmacokinetic data between MOX and OFX, a breakpoint MIC of 2 mg/L was suggested for MOX in the MGIT system. All but two OFX-resistant isolates possessed MIC of MOX of 2 mg/L or lower and were considered to be susceptible to MOX; however, all OFX-resistant strains studied had mutations involved in resistance to quinolones. DNA sequence analysis for the gyrase A mutation, which was an indicator for OFX resistance, correlated with MOX susceptibility changes. Significant decreases in MOX susceptibility amongst MDR-MTB strains were observed that correlated with OFX susceptibility. The Asp94Gly mutation appeared to be associated with a higher level of MICs to both OFX and MOX. These findings on the stepwise decline of in vitro susceptibility to MOX suggest that clinical usage of MOX should be accompanied by careful monitoring of susceptibility to this important anti-MDR MTB drug.

New drug candidates and therapeutic targets for tuberculosis therapy

Despite advances in chemotherapy and the BCG (Bacillus Calmette-Guérin) vaccine, tuberculosis remains a significant infectious disease. Although it can be cured, the therapy takes at least 6-9 months, and the laborious and lengthy treatment brings with it dangers of noncompliance, significant toxicity and drug resistance. The increasing emergence of drug resistance and the problem of mycobacterial persistence highlight the need to develop novel TB drugs that are active against drug resistant bacteria but, more importantly, kill persistent bacteria and shorten the length of treatment. Recent new and exciting developments in tuberculosis drug discovery show good promise of a possible revolution in the chemotherapy of tuberculosis.

Early bactericidal activity of a moxifloxacin and isoniazid combination in smear-positive pulmonary tuberculosis

BACKGROUND

In vitro and animal studies have shown that moxifloxacin-containing combinations may improve the bactericidal efficacy of antituberculosis regimens.

PATIENTS AND METHODS

We measured the decline in the sputum viable count of 13 patients who were given a combination of moxifloxacin 400 mg daily and isoniazid 300 mg daily.

RESULTS

The time required to reduce the viable count by 50% (vt50) was 0.38 days (95% CI -0.03-0.78 days, SEM 0.13) and the mean early bactericidal activity (EBA) was 0.60 log10 cfu/day (95% CI 0.23-0.97, SEM 0.14). This compares with the vt50 calculated for isoniazid and moxifloxacin alone in the same population of 0.48 and 0.88 days, respectively. The EBA values for isoniazid and moxifloxacin alone were 0.77 and 0.53 log10 cfu/day, respectively.

CONCLUSIONS

The combination of moxifloxacin and isoniazid is not antagonistic, but the combination does not significantly enhance bactericidal activity above that of isoniazid alone.

Intracameral Vigamox (moxifloxacin 0.5%) is non-toxic and effective in preventing endophthalmitis in a rabbit model

PURPOSE

To determine whether Vigamox (moxifloxacin 0.5% ophthalmic solution) can be safely injected intracamerally to prevent Staphylococcus aureus endophthalmitis in a rabbit model.

DESIGN

Animal study.

METHODS

The safety and bactericidal-effectiveness of Vigamox were evaluated in three stages using 189 New Zealand White rabbits. (Stage 1) The toxicity of two intravitreal doses of Vigamox (moxifloxacin 500, 250 microg) was compared with vancomycin (1 mg) and saline. (Stage 2) A reproducible rabbit model of Staphylococcus aureus endophthalmitis was established. (Stage 3) The bactericidal effect of intracameral Vigamox (moxifloxacin 500, 250, 125, 50 microg) was compared with vancomycin (1 mg) and saline. Intracameral antibiotic therapy commenced immediately after Staphylococcus aureus intravitreal challenge (5000 cfu). Toxicity was evaluated by masked clinical examination using a slit-lamp, an indirect ophthalmoscope, and corneal-ultrasound pachymetry. The clinical examination included the exterior eye, cornea, anterior chamber, vitreous, and retina. The presentations were graded on a severity scale of 0, 0.5, 1, 2, and 3. The bactericidal efficacy was determined using intracameral colony counts.

RESULTS

In the toxicity studies without bacterial challenge, the clinical scores of rabbits injected intracamerally with Vigamox were statistically equivalent to rabbits given intracameral vancomycin or saline. In the efficacy studies, eyes treated intravitreally with Vigamox, at all doses, or vancomycin were negative for Staphylococcus aureus and nontreated controls remained culture-positive.

CONCLUSIONS

Vigamox appears to be nontoxic for intracameral injection and effective in preventing experimental endophthalmitis in the rabbit model. Further studies will determine the clinical role of intracameral Vigamox for surgical prophylaxis and postoperative therapy.

Quinolones in 2005: an update

Quinolones are one of the largest classes of antimicrobial agents used worldwide. This review considers the quinolones that are available currently and used widely in Europe (norfoxacin, ciprofloxacin, ofloxacin, levofloxacin and moxifloxacin) within their historical perspective, while trying to position them in the context of recent and possible future advances based on an understanding of: (1) their chemical structures and how these impact on activity and toxicity; (2) resistance mechanisms (mutations in target genes, efflux pumps); (3) their pharmacodynamic properties (AUC/MIC and Cmax/MIC ratios; mutant prevention concentration and mutant selection window); and (4) epidemiological considerations (risk of emergence of resistance, clonal spread). Their main indications are examined in relation to their advantages and drawbacks. Overall, it is concluded that these important agents should be used in an educated fashion, based on a careful balance between their ease of use and efficacy vs. the risk of emerging resistance and toxicity. However, there is now substantial evidence to support use of the most potent drug at the appropriate dose whenever this is required.

Fluoroquinolones for treating tuberculosis

BACKGROUND

Fluoroquinolones are sometimes used to treat multiple-drug-resistant and drug-sensitive tuberculosis. The effects of fluoroquinolones in tuberculosis regimens need to be assessed.

OBJECTIVES

To assess fluoroquinolones as additional or substitute components to antituberculous drug regimens for drug-sensitive and drug-resistant tuberculosis.

SEARCH STRATEGY

We searched the Cochrane Infectious Diseases Group Specialized Register (April 2005), CENTRAL (The Cochrane Library Issue 1, 2005), MEDLINE (1966 to April 2005), EMBASE (1974 to April 2005), LILACS (1982 to April 2005), Science Citation Index (1940 to April 2005), and Russian database (1988 to April 2005). We also scanned reference lists of all identified studies and contacted researchers.

SELECTION CRITERIA

Randomized controlled trials of antituberculous regimens containing fluoroquinolones in people diagnosed with bacteriologically positive (sputum smear or culture) pulmonary tuberculosis.

DATA COLLECTION AND ANALYSIS

Two authors independently applied inclusion criteria, assessed methodological quality, and extracted data. We used relative risk (RR) for dichotomous data, weighted mean difference (WMD) for continuous data (both with 95% confidence intervals (CI)), and the random-effects model if we detected heterogeneity and appropriate to combine data.

MAIN RESULTS

Ten trials (1178 participants) met the inclusion criteria. No statistically significant difference was found in trials substituting ciprofloxacin or ofloxacin for first-line drugs in relation to cure (89 participants, 2 trials), treatment failure (388 participants, 3 trials), or clinical or radiological improvement (216 participants, 2 trials). Substituting ciprofloxacin into first-line regimens in drug-sensitive tuberculosis led to a higher incidence of relapse (RR 7.17, 95% CI 1.33 to 38.58; 384 participants, 3 trials) and longer time to sputum culture conversion (WMD 0.50 months, 95% CI 0.18 to 0.82; 168 participants, 1 trial), although this was confined to HIV-positive participants. Adding or substituting levofloxacin to basic regimens in drug-resistant areas had no effect. A comparison of sparfloxacin versus ofloxacin added to regimens showed no statistically significant difference in cure (184 participants, 2 trials), treatment failure (149 participants, 2 trials), or total number of adverse events (253 participants, 3 trials).

AUTHORS' CONCLUSIONS

Only ciprofloxacin, ofloxacin, levofloxacin, and sparfloxacin have been tested in randomized controlled trials for treating tuberculosis. We cannot recommend ciprofloxacin in treating tuberculosis. Trials of newer fluoroquinolones for treating tuberculosis are needed. No difference has been demonstrated between sparfloxacin and ofloxacin in drug-resistant tuberculosis.

New Drugs for Tuberculosis: Current Status and Future Prospects

This article reviews two classes of compounds that have advanced into phase II and III clinical trials, long-acting rifamycins and fluoroquinolones, and a number of other drugs that have entered or may enter clinical development in the near future.

The magic bullets and tuberculosis drug targets

Modern chemotherapy has played a major role in our control of tuberculosis. Yet tuberculosis still remains a leading infectious disease worldwide, largely owing to persistence of tubercle bacillus and inadequacy of the current chemotherapy. The increasing emergence of drug-resistant tuberculosis along with the HIV pandemic threatens disease control and highlights both the need to understand how our current drugs work and the need to develop new and more effective drugs. This review provides a brief historical account of tuberculosis drugs, examines the problem of current chemotherapy, discusses the targets of current tuberculosis drugs, focuses on some promising new drug candidates, and proposes a range of novel drug targets for intervention. Finally, this review addresses the problem of conventional drug screens based on inhibition of replicating bacilli and the challenge to develop drugs that target nonreplicating persistent bacilli. A new generation of drugs that target persistent bacilli is needed for more effective treatment of tuberculosis.

Moxifloxacin (Avelox): a novel fluoroquinolone with a broad spectrum of activity

Moxifloxacin (Avelox) is a recently-developed fluoroquinolone that has a broad spectrum of antimicrobial activity, including typical respiratory pathogens, atypical and intracellular respiratory pathogens, Gram-negative pathogens and many anaerobes. This spectrum of activity makes moxifloxacin particularly suitable for the therapy of community-acquired respiratory tract infections. It also has enhanced activity against specific bacteria, such as Mycobacteria spp. and Legionella. Moxifloxacin has pharmacologic characteristics that support once-daily dosing regimens and dual routes of excretion that require little or no adjustment for renal or hepatic insufficiency. The drug has maintained an excellent safety profile based upon broad global usage, and no adverse events have occurred that were unanticipated. Streptococcus pneumoniae, which are resistant to earlier fluoroquinolones, are less likely to be resistant to moxifloxacin.

Moxifloxacin-containing Regimen Greatly Reduces Time to Culture Conversion in Murine Tuberculosis

Tuberculosis continues to be a major cause of morbidity and mortality in the world. The expansion of tuberculosis control programs has been limited by the lengthy and cumbersome nature of current chemotherapeutic regimens. A new drug that improves the sterilizing activity of current regimens would reduce the duration of therapy without sacrificing efficacy, thereby enhancing treatment completion rates and preserving precious public health resources. The new 8-methoxyfluoroquinolone moxifloxacin has potent activity against both actively multiplying and nonactively multiplying tubercle bacilli. Using a murine model that is representative of chemotherapy for human tuberculosis, we show that the combination of moxifloxacin, rifampin, and pyrazinamide reduced the time needed to eradicate Mycobacterium tuberculosis from the lungs of infected mice by up to 2 months when compared with the standard regimen of isoniazid, rifampin, and pyrazinamide. The findings suggest that this regimen has the potential to substantially shorten the duration of therapy needed to cure human tuberculosis.

Tuberculosis

Among communicable diseases, tuberculosis is the second leading cause of death worldwide, killing nearly 2 million people each year. Most cases are in less-developed countries; over the past decade, tuberculosis incidence has increased in Africa, mainly as a result of the burden of HIV infection, and in the former Soviet Union, owing to socioeconomic change and decline of the health-care system. Definitive diagnosis of tuberculosis remains based on culture for Mycobacterium tuberculosis, but rapid diagnosis of infectious tuberculosis by simple sputum smear for acid-fast bacilli remains an important tool, and more rapid molecular techniques hold promise. Treatment with several drugs for 6 months or more can cure more than 95% of patients; direct observation of treatment, a component of the recommended five-element DOTS strategy, is judged to be the standard of care by most authorities, but currently only a third of cases worldwide are treated under this approach. Systematic monitoring of case detection and treatment outcomes is essential to effective service delivery. The proportion of patients diagnosed and treated effectively has increased greatly over the past decade but is still far short of global targets. Efforts to develop more effective tuberculosis vaccines are under way, but even if one is identified, more effective treatment systems are likely to be required for decades. Other modes of tuberculosis control, such as treatment of latent infection, have a potentially important role in some contexts. Until tuberculosis is controlled worldwide, it will continue to be a major killer in less-developed countries and a constant threat in most of the more-developed countries.

Fluoroquinolones, tuberculosis, and resistance

Although the fluoroquinolones are presently used to treat tuberculosis primarily in cases involving resistance or intolerance to first-line antituberculosis therapy, these drugs are potential first-line agents and are under study for this indication. However, there is concern about the development of fluoroquinolone resistance in Mycobacterium tuberculosis, particularly when administered as monotherapy or as the only active agent in a failing multidrug regimen. Treatment failures as well as relapses have been documented under such conditions. With increasing numbers of fluoroquinolone prescriptions and the expanded use of these broad-spectrum agents for many infections, the selective pressure of fluoroquinolone use results in the ready emergence of fluoroquinolone resistance in a diversity of organisms, including M tuberculosis. Among M tuberculosis, resistance is emerging and may herald a significant future threat to the long-term clinical utility of fluoroquinolones. Discussion and education regarding appropriate use are necessary to preserve the effectiveness of this antibiotic class against the hazard of growing resistance.