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* From the Division of Respiratory Medicine University of Calgary Medical School and Calgary Health Region Tuberculosis Services, Calgary, AB, Canada.
Correspondence to: Stephen K. Field, MD, CM, FCCP, Foothills Hospital, 1403 29th St NW Calgary, AB, Canada T2N 2T9; e-mail sfield{at}ucalgary.ca
| Abstract |
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Methods: Consecutive individuals referred for treatment of MAC lung disease were treated with a regimen that included either clarithromycin, 500 mg bid, or azithromycin, 250 mg/d, on weekdays; ethambutol, 15 mg/kg/d; and clofazimine, 100 mg/d. The intention was to treat patients for a minimum of 12 months. The diagnosis of MAC lung disease was confirmed by multiple positive sputum culture findings in patients with typical symptoms and radiologic findings.
Results: Thirty patients (27 women and 3 men; mean age, 70 ± 9.4 years [SD]) were treated. A total of 22 of the patients reported adverse effects from clarithromycin or azithromycin. Intolerance of clarithromycin resulted in the withdrawal of four patients before sputum conversion. The remaining patients continued treatment for an average of 10 months, and sputum findings converted to negative in all 26 patients (87%). One patient died of unrelated causes while still receiving therapy, and five patients (19%) relapsed an average of 17 months after treatment was completed.
Conclusions: Treatment with a macrolide, ethambutol, and clofazimine was successful in 20 of 30 patients (67%) with MAC lung disease and is a reasonable alternative to rifamycin-containing regimens.
Key Words: azithromycin bronchiectasis clarithromycin clofazimine ethambutol Mycobacterium avium
| Introduction |
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The University of Texas group based at Tyler, TX, and others12 13 14 15 16 17 18 19 20 21 have shown that both clarithromycin and azithromycin are active against MAC lung disease in patients without HIV infections either when administered alone or in combination with other medications. To avoid the emergence of resistant organisms, it is recommended that MAC lung disease be treated with a macrolide in combination with two or three other medications. The American Thoracic Society statement on the diagnosis and treatment of disease caused by NTM, published in 1997, recommends that MAC pulmonary disease be treated with a combination of a macrolide, either clarithromycin or azithromycin; a rifamycin, either rifabutin or rifampin; and ethambutol until sputum culture findings have been negative for at least 1 year.22 It also recommends that streptomycin be administered for the first 8 weeks of therapy to facilitate a rapid decline in the number of organisms. Unfortunately, long-term treatment with these medications is not well tolerated by the elderly. Studies15 16 17 with intermittent therapy have been undertaken to attempt to reduce drug intolerance, but side effects remain a limiting factor.
Rifabutin is the more active rifamycin against MAC, but side effects believed to be of an immune nature, including the development of polyarthralgias, anterior uveitis, and leukopenia, may be severe enough to require withdrawal of the drug.23 24 25 26 Rifampin is not as active against MAC as rifabutin but causes fewer adverse effects. Unfortunately, it affects the metabolism of other drugs through its action on the hepatic cytochrome P-450 system.13 Both rifabutin and rifampin lower serum levels of clarithromycin and its 14-hydroxy metabolite.27 Most patients with MAC lung disease are elderly and may have comorbid conditions that are adversely affected by drug interactions with rifampin. Clarithromycin is a cytochrome P-450 3A4 isoenzyme inhibitor and may increase serum levels of several drugs including rifabutin.28 Drug/drug interactions involving clarithromycin may account for some of the intolerability of this drug in the elderly. Aminoglycosides are administered by injection and have serious side effects including renal failure and ototoxicity that can be manifested as hearing loss or vestibular dysfunction.22
This article reports the results of treatment with a regimen containing ethambutol and clofazimine as companion drugs to clarithromycin or azithromycin for treatment of MAC lung disease in patients without HIV infection, sparing them the need for treatment with and the potential side effects of the rifamycins and aminoglycosides. Clofazimine was chosen as the second companion drug because the provincial tuberculosis laboratory used to report sensitivities for NTM isolates and local MAC isolates were uniformly sensitive to it. Another advantage is that it is generally well tolerated, even in the elderly.
| Materials and Methods |
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Patients referred to the Calgary Health Region Tuberculosis Clinic with MAC lung disease who were
18 years were considered for inclusion. Patients could be inpatients or outpatients. Exclusion criteria included macrolide intolerance or allergy, pregnancy, inadequate contraception, known infection with a macrolide-resistant organism, and risk factors for or known HIV positivity. Patients were eligible for inclusion in the analysis regardless of previous MAC therapy as long as the pretreatment isolate was not macrolide resistant.
Specimen Preparation
Unless sputum was readily produced, it was induced using 5% nebulized saline solution. Sputum specimens were decontaminated with equal amounts of 4% sodium hydroxide. Sputum specimens were examined with a rhodamine-auramine fluorescent stain, and positive smears were confirmed with Ziehl-Neelsen staining. All specimens were cultured. Cultured specimens were checked weekly for a minimum of 7 weeks. All sputum specimens demonstrating growth underwent Ziehl-Neelsen staining and were examined with DNA probes. MAC probe-positive specimens were reported and were sent for sensitivity testing. Susceptibility testing was done in our provincial laboratory by the standardized method recommended by the National Committee for Laboratory Standards.29
Therapy
All patients were treated with clarithromycin, 500 mg bid po, or azithromycin 250 mg/d po, on weekdays, together with ethambutol, approximately 15 mg/kg/d po, and clofazimine 100 mg/d po. The aim was to provide the treatment regimen for a total of 1 year or at least 6 months after the sputum culture finding became negative, whichever was longer. To be included in the analysis, all patients had been followed up for at least 6 months after stopping treatment.
Drug Safety Tests
Prior to initiation of drug therapy and at each subsequent clinic visit, patients were questioned about problems and symptoms. Patients were instructed about potential side effects prior to initiating therapy and questioned about these at each visit during therapy. Patients were instructed to contact the clinic, which was open 5 days per week, with any concerns or symptoms between visits. Blood work including a CBC count, differential cell count, and liver function tests were done at baseline and every 2 months while receiving therapy for safety reasons. Eye examinations were performed at baseline and repeated at 2-month intervals. Patients were only given a 1-month supply of medication and came to the clinic to receive monthly refills, at which time medication containers were checked to verify adherence to the prescribed regimen. Records were kept of sputum culture results and side effects.
Statistical Analysis
Group results are expressed as mean ± SD. Comparisons between groups were done by paired t tests for continuous variables and by
2 analysis for categorical data.
| Results |
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1 year) for those who were receiving azithromycin at the end of their treatment period: 7 of 14 patients receiving azithromycin compared with 3 of 16 patients receiving clarithromycin (p = 0.07). Three patients complained about the change in skin color associated with clofazimine. Two patients complained of visual disturbance, necessitating withdrawal of ethambutol in one patient.
| Discussion |
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Research trials of MAC lung disease are difficult to perform because of the small number of patients in any one center. MAC lung disease is slowly progressive, and responses to treatment are relatively slow.2 3 4 22 It is hard to compare the published studies too closely since patient selection criteria, sputum criteria for diagnosis, surveillance during and after the completion of therapy, and criteria for defining a successful outcome differ.3 Some studies included patients who had been treated previously for MAC and some included patients with defined immunodeficiency disorders. Gender proportions, and pattern and extent of lung disease also varied in different studies. In most of the published clinical trials of treatment with macrolides, a large proportion of the patients required a change from the planned treatment protocol because of side effects.
The most common complaint related to the use of clarithromycin was taste perversion, which was most often associated with loss of appetite and with nausea.19 30 These were the complaints of the four patients in whom treatment failed. Patients receiving azithromycin generally complained of diarrhea, with nausea and dyspepsia being less common. These side effects were often not severe and generally resolved with continued use of the drug.31
All patients who were able to tolerate a minimum of 5 months of treatment converted their sputum to negative, whereas none of the four who were unable to tolerate 4 months of therapy converted their sputum findings to negative. Five of the 26 patients relapsed an average of 17 months after stopping therapy. The relapse rate with this regimen was comparable to the results of other macrolide- containing regimens.12 13 19
In the patients who relapsed, the MAC organisms retained their susceptibility to clarithromycin and azithromycin, and all converted their sputum findings to negative with retreatment. It may be that apparent relapse actually represents reinfection rather than relapse. Genetic studies32 have demonstrated that a single strain of MAC tends to persist in patients with fibrocavitary lung, whereas different strains are found over time in patients with fibronodular bronchiectasis. Most of our patients and those in other reports of macrolide-containing regimens have the fibronodular bronchiectasis form of MAC lung disease. The long-term success of both this and other regimens will need to be assessed by studies with longer follow-up periods.
It is uncertain why some people without an obvious immunodeficiency disorder or preceding lung disease acquire MAC lung disease. A study33
compared cytokine profiles in patients with MAC lung disease to control subjects who were infected with MAC, as determined by a positive delayed-type hypersensitivity response to MAC sensitin, and a negative tuberculin skin test reaction, but who were healthy. The monocytes from the control subjects produced higher concentrations of interferon-
and tumor necrosis factor-
, cytokines that have been shown to contribute to host defenses against tuberculosis and MAC in animals.33
Patients with cystic fibrosis also appear to be predisposed to NTM infection including MAC lung disease.34
It is likely that those who may be predisposed to MAC infection will continue to be at risk for infection whether they do or do not have underlying lung disease.33
These patients should be followed up indefinitely, as was formerly the case for patients with a history of tuberculosis, and treated again if necessary.
It appears that MAC lung disease, especially fibronodular bronchiectasis, is becoming more common.1 2 This may be due to the aging of the population and/or a greater awareness of the role of MAC in the pathogenesis of bronchiectasis. As the awareness of the role of MAC increases, especially in patients with chronic respiratory symptoms, the reported prevalence will probably increase. Patients with bronchiectasis, especially when it occurs late in life or primarily affects the lingula and/or the right middle lobe, should have sputum sent for mycobacterial culture.35
Most studies of the treatment of MAC lung disease have been case series because of the small numbers treated in any one institution. An exception was the British Thoracic Society study published in 2001.8 Unfortunately, it was conceived before the newer macrolides were available, and the results are no longer relevant. Hopefully, further multicenter trials will be undertaken both to better understand the natural history of this condition and to help define optimal therapy for this condition.
| Footnotes |
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Presented in abstract form at the American Thoracic Society Meeting in Atlanta, GA, May 1722, 2002.
Received for publication December 27, 2002. Accepted for publication May 27, 2003.
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