Activities of various macrolide antibiotics against Mycobacterium leprae infection in mice

Pharmacokinetics of extended-release clarithromycin in patients with Mycobacterium ulcerans infection

Clarithromycin extended-release (CLA-ER) was used as companion drug to rifampicin (RIF) for Mycobacterium ulcerans infection in the intervention arm of a WHO drug trial. RIF enhances CYP3A4 metabolism, thereby reducing CLA serum concentrations, and RIF concentrations might be increased by CLA co-administration. We studied the pharmacokinetics of CLA-ER at a daily dose of 15 mg/kg combined with RIF at a dose of 10 mg/kg in a subset of trial participants, and compared these to previously obtained pharmacokinetic data. Serial dried blood spot samples were obtained over a period of ten hours, and analyzed by LC-MS/MS in 30 study participants-20 in the RIF-CLA study arm, and 10 in the RIF-streptomycin study arm. Median CLA Cmax was 0.4 mg/L-and median AUC 3.9 mg*h/L, following 15 mg/kg CLA-ER. Compared to standard CLA dosed at 7.5 mg/kg previously, CLA-ER resulted in a non-significant 58% decrease in Cmax and a non-significant 30% increase in AUC. CLA co-administration did not alter RIF Cmax or AUC. Treatment was successful in all study participants. No effect of CLA co-administration on RIF pharmacokinetics was observed. Based on our serum concentration studies, the benefits CLA-ER over CLA immediate release are unclear.

Treatment and Evaluation Advances in Leprosy Neuropathy

Neuropathy and related disabilities are the major medical consequences of leprosy, which remains a global medical concern. Despite major advances in understanding the mechanisms of M. leprae entry into peripheral nerves, most aspects of the pathogenesis of leprosy neuropathy remain poorly understood. Sensory loss is characteristic of leprosy, but neuropathic pain is sometimes observed. Effective anti-microbial therapy is available, but neuropathy remains a problem especially if diagnosis and treatment are delayed. Currently there is intense interest in post-exposure prophylaxis with single-dose rifampin in endemic areas, as well as with enhanced prophylactic regimens in some situations. Some degree of nerve involvement is seen in all cases and neuritis may occur in the absence of leprosy reactions, but acute neuritis commonly accompanies both Type 1 and Type 2 leprosy reactions and may be difficult to manage. A variety of established as well as new methods for the early diagnosis and assessment of leprosy neuropathy are reviewed. Corticosteroids offer the primary treatment for neuritis and for subclinical neuropathy in leprosy, but success is limited if nerve function impairment is present at the time of diagnosis. A candidate vaccine has shown apparent benefit in preventing nerve injury in the armadillo model. The development of new therapeutics for leprosy neuropathy is greatly needed.

Insights of synthetic analogues of anti-leprosy agents

Today, the emergence of the phenomenon of drug or multidrug-resistance for community-associated diseases represents a major concern in the world. In these contexts, the chronic infectious disease, leprosy, grounded by a slow-growing bacterium called Mycobacterium leprae or Mycobacterium lepromatosis is a leadingcause of severe disfiguring skin sores and nerve damage in the arms, legs, and skin areas around the body. Even, over 200,000 new leprosy cases are being accounted every year along with the relapsed leprosy cases. Nonetheless, this has been considered a curable disease with a higher dose of multidrug therapy (MDT) for a long period of time. The prolonged action of a high dose of combination drugs administration may cause an adverse reaction that can significantly affect patient compliance, particularly the outbreak of multidrug-resistance in the infected person. To overcome these shortfalls or prevent the resistance-associated problems, researchers are diligently involved in the structural modifications of the clinically used anti-leprosy drugs or the allied compounds for the structure-antimycobacterial activity relationship study. This review article described the detailed synthesis and biological assays of different anti-leprosy compounds reported by several research groups.

The diarylquinoline R207910 is bactericidal against Mycobacterium leprae in mice at low dose and administered intermittently

The diarylquinoline R207910 is profoundly bactericidal in a murine model of tuberculosis. Previously, R207910 was also found to be bactericidal for Mycobacterium leprae-infected mice during lag phase. Herein we evaluate the bactericidal efficacy of R207910 (1 to 120 mg/kg of body weight) when administered five times weekly, once weekly, and once monthly during logarithmic multiplication of M. leprae organisms. All treatments were found to be bactericidal, suggesting that both low and intermittent dosing with R207910 holds promise for leprosy patients.

A guide to selection and appropriate use of macrolides in skin infections

Dermatologists must be aware of the adverse effects of antimicrobial agents as well as various drug interactions that may influence the choice of drug as well as specific drug schedules. The development of modern antibacterials has improved the treatment of cutaneous bacterial infections. Macrolide antibacterials continue to be an important therapeutic class of drugs with established efficacy in a variety of skin infections. All macrolides inhibit protein synthesis by reversibly binding to the 23S ribosomal RNA in the 50S-subunit. Erythromycin, the prototype of macrolide antibacterials, was isolated from the metabolic products of a strain of Streptomyces erytherus in 1952. Originally, erythromycin was introduced as an alternative to penicillin because of its activity against the Gram-positive organisms. Numerous studies have demonstrated the efficacy and safety of erythromycin for various infectious diseases. Unfortunately, erythromycin is associated with a number of drawbacks including a narrow spectrum of activity, unfavorable pharmacokinetic properties, poor gastrointestinal tolerability, and a significant number of drug-drug interactions. Newer macrolides have been developed to address these limitations. The pharmacokinetics of azithromycin and clarithromycin allow for shorter dosing schedules because of prolonged tissue levels. The efficacy of azithromycin for the treatment of skin and soft tissue infections in adults and children is well established. The unique pharmakinetics of azithromycin makes it a suitable agent for the treatment of acne. Clarithromycin represents a clear advance in the macrolide management of patients with leprosy and skin infections with atypical mycobacteria. Dirithromycin and roxithromycin display no clinical or bacteriological adcantage over erythromycin despite a superior pharmacokinetic profile. An area of concern is the increasing macrolide resistance that is being reported with some of the common pathogens which may limit the clinical usefulness of this class of antimicrobial agents in future.

Systemic antibiotic agents

Understanding the breadth of systemic antimicrobial agents available for use by the dermatologist and their associated side-effect profiles and drug interactions allows the clinician to offer patients optimal care in the management of cutaneous infectious disease.

The macrolides: erythromycin, clarithromycin, and azithromycin

In addition to erythromycin, macrolides now available in the United States include azithromycin and clarithromycin. These two new macrolides are more chemically stable and better tolerated than erythromycin, and they have a broader antimicrobial spectrum than erythromycin against Mycobacterium avium complex (MAC), Haemophilus influenzae, nontuberculous mycobacteria, and Chlamydia trachomatis. All three macrolides have excellent activity against the atypical respiratory pathogens (C. pneumoniae and Mycoplasma species) and the Legionella species. Azithromycin and clarithromycin have pharmacokinetics that allow shorter dosing schedules because of prolonged tissue levels. Both azithromycin and clarithromycin are active agents for MAC prophylaxis in patients with late-stage acquired immunodeficiency syndrome (AIDS), although azithromycin may be the preferable agent because of fewer drug-drug interactions. Clarithromycin is the most active MAC antimicrobial agent and should be part of any drug regimen for treating active MAC disease in patients with or without AIDS. Although both azithromycin and clarithromycin are well tolerated by children, azithromycin has the advantage of shorter treatment regimens and improved tolerance, potentially improving compliance in the treatment of respiratory tract and skin or soft tissue infections. Intravenously administered azithromycin has been approved for treatment of adults with mild to moderate community-acquired pneumonia or pelvic inflammatory diseases. An area of concern is the increasing macrolide resistance that is being reported with some of the common pathogens, particularly Streptococcus pneumoniae, group A streptococci, and H. influenzae. The emergence of macrolide resistance with these common pathogens may limit the clinical usefulness of this class of antimicrobial agents in the future.

Antimicrobial agents for the dermatologist. II. Macrolides, fluoroquinolones, rifamycins, tetracyclines, trimethoprim-sulfamethoxazole, and clindamycin

This article is the second of a two-part series reviewing antimicrobial agents that are used by the dermatologist. In part I we reviewed beta-lactam antibiotics and related compounds. In this section we again emphasize some newer agents (macrolides, fluoroquinolones) as well as some of the more commonly employed older agents (rifamycins, tetracyclines, trimethoprim-sulfamethoxazole, and clindamycin.

Choosing the right macrolide antibiotic. A guide to selection

Macrolide antibiotics have proven to be valuable alternatives to penicillins and cephalosporins for the treatment of a number of infections. Currently, a number of macrolides are available. When choosing a particular macrolide, the types of organisms causing the infection, the tolerability of the drug, convenience of dosing and possible drug interactions all must be taken into account. Erythromycin, azithromycin and clarithromycin are equally effective against most gram-positive organisms. However, clarithromycin and azithromycin have much better activity against Haemophilus influenza and Moraxella catarrhalis. Thus, these 2 drugs are better choices for the treatment of community-acquired pneumonia. However, the low serum concentrations of azithromycin may be a problem in patients with bacteraemia associated with with community-acquired pneumonia. Clarithromycin appears to be effective for the treatment and prophylaxis of Mycobacterium avium complex (MAC) in patients with AIDS, while azithromycin appears to be effective for prophylaxis. Treatment of MAC with azithromycin is currently undergoing study. Although clarithromycin is the macrolide of choice for the treatment of Helicobacter pylori, azithromycin is the preferred macrolide for the treatment of Chlamydia trachomatis infections. The major factor limiting the use of azithromycin and clarithromycin has been their cost. However, these drugs may be cost effective if compliance is improved due to better tolerability and more convenient dosing regimens.

Chemotherapy of lepromatous leprosy: recent developments and prospects for the future

Leprosy is a major debilitating infectious disease, primarily of the developing world. In this paper the current status and future prospects of antimicrobial therapy of the severe anergic lepromatous form of the disease are reviewed. Until the last few years only dapsone, rifampicin, clofazimine and ethionamide have had practical application in its therapy, and only rifampicin was bactericidal. Recently, antibiotics from three different classes have been found to be bactericidal in lepromatous patients: a tetracycline (minocycline), a macrolide (clarithromycin), and several fluoroquinolones (including pefloxacin, ofloxacin and sparfloxacin). Against a background of drug resistance and bacterial persistence, recommendations for multidrug therapy and the means to devise rationally based therapy for the future are discussed.

Roxithromycin. An update of its antimicrobial activity, pharmacokinetic properties and therapeutic use

Roxithromycin is a derivative of the macrolide antibacterial erythromycin with in vitro antibacterial activity resembling that of the parent compound. The drug has activity against some Staphylococcus spp., many Streptococcus spp., Moraxella (Branhamella) catarrhalis, Mycoplasma pneumoniae, Legionella pneumophila and Chlamydia trachomatis as well as many less common organisms. Measured using recently proposed guidelines, roxithromycin has in vitro activity against Haemophilus influenzae. In comparison with that of its parent compound, the pharmacokinetic profile of roxithromycin is characterised by high plasma, tissue and body fluid concentrations and a long half-life permitting an extended dosage interval. Roxithromycin has proven clinical efficacy in upper and lower respiratory infections, skin and soft tissue infections, urogenital infections and orodental infections, and appears to be as effective as more established treatments including erythromycin, amoxicillin/clavulanic acid and cefaclor. The drug has also shown promise in a variety of more specialised indications including opportunistic infections in human immunodeficiency virus (HIV)-positive patients and as part of a Helicobacter pylori eradication regimen. Roxithromycin is very well tolerated with an overall incidence of adverse events of approximately 4%. Thus, roxithromycin is an attractive therapeutic alternative in its established indications, especially when the option of once-daily administration is considered.

Activities of azithromycin and clarithromycin against nontuberculous mycobacteria in beige mice

The comparative activities of azithromycin (AZI) and clarithromycin (CLA) were evaluated against nontuberculous mycobacteria in a murine model of disseminated infection. Four-week-old beige mice (C57BL/6J bgj/bgj) were infected intravenously with approximately 10(7) viable Mycobacterium kansasii, M. xenopi, M. simiae, or M. malmoense. Treatment with AZI at 200 mg/kg, CLA at 200 mg/kg, ethambutol at 125 mg/kg, rifampin at 20 mg/kg, or clofazimine at 20 mg/kg of body weight was started 7 days postinfection, and the treatments were administered 5 days per week for 4 weeks. Control groups were sacrificed at the start and end of the treatments. Spleens and lungs were homogenized, and viable cell counts were determined by serial dilution and plating onto 7H10 agar. AZI and CLA had activities comparable to or better than that of rifampin, ethamutol, or clofazimine against these nontuberculous mycobacteria in the beige mouse test system. AZI at 200 mg/kg was more active than CLA at 200 mg/kg against organisms in the spleens for M. xenopi and M. malmoense. The activities of AZI and CLA were comparable against organisms in the spleens for M. kansasii and M. simiae. The activities of these two agents were comparable against organisms in the lungs for all four nontuberculous mycobacterial species. AZI or CLA in combination with other agents may be useful for the therapy of nontuberculous mycobacterial infections in humans.

Clinical trial of clarithromycin for lepromatous leprosy

Clarithromycin was administered to nine previously untreated lepromatous leprosy patients. Patients received two 1,500-mg doses on the first day, followed by 7 days of no treatment, in order to evaluate the potential efficacy of intermittent therapy. Patients then received 1,000 mg daily for 2 weeks followed by 500 mg daily for 9 weeks. The efficacy of therapy was monitored clinically, by changes in morphological index, mouse footpad infectivity, and radiorespirometric activity of Mycobacterium leprae obtained from serial biopsies and by serum levels of phenolic glycolipid I. Clarithromycin was well tolerated, with only minor side effects noted in two patients. Most patients showed reductions in morphological index and radiorespirometry 1 week after the first two doses. Within 3 weeks of starting treatment (total of 17 g of clarithromycin), biopsy-derived M. leprae specimens from all patients had a morphological index of zero, were noninfectious for mice, and had less than 1% of the radiorespirometric activity of pretreatment specimens. Reductions in serum phenolic glycolipid I levels were observed for most patients at 3 weeks. Significant clinical improvement was evident after 4 weeks of treatment. All analyses indicate that clarithromycin is rapidly bactericidal for M. leprae in humans.

Hansen's disease

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Semi-synthetic derivatives of erythromycin

Semi-synthetic derivatives of erythromycin have played an important role in antimicrobial chemotherapy. First generation derivatives such as 2'-esters and acid-addition salts significantly improved the chemical stability and oral bioavailability of erythromycin. A second generation of erythronolide-modified derivatives: roxithromycin, clarithromycin, azithromycin, dirithromycin and flurithromycin, have been synthesized and have exhibited significant improvements in pharmacokinetic and/or microbiological features. In addition, erythromycin itself has expanded its utility as an effective antibiotic against a variety of newly emerged pathogens. As a result of these developments, macrolide antibiotics have enjoyed a resurgence in clinical interest and use during the past half-dozen years, and semi-synthetic derivatives of erythromycin should continue to be important contributors to this macrolide renaissance. Despite these recent successes, other useful niches for macrolide antibiotics will remain unfilled. Consequently, the search for new semi-synthetic derivatives of erythromycin possessing even better antimicrobial properties should be pursued.

Azithromycin. A review of its antimicrobial activity, pharmacokinetic properties and clinical efficacy

Azithromycin is an acid stable orally administered macrolide antimicrobial drug, structurally related to erythromycin, with a similar spectrum of antimicrobial activity. Azithromycin is marginally less active than erythromycin in vitro against Gram-positive organisms, although this is of doubtful clinical significance as susceptibility concentrations fall within the range of achievable tissue azithromycin concentrations. In contrast, azithromycin appears to be more active than erythromycin against many Gram-negative pathogens and several other pathogens, notably Haemophilus influenzae, H. parainfluenzae, Moraxella catarrhalis, Neisseria gonorrhoeae, Urea-plasma urealyticum and Borrelia burgdorferi. Like erythromycin and other macrolides, the activity of azithromycin is unaffected by the production of beta-lactamase. However, erythromycin-resistant organisms are also resistant to azithromycin. Following oral administration, serum concentrations of azithromycin are lower than those of erythromycin, but this reflects the rapid and extensive movement of the drug from the circulation into intracellular compartments resulting in tissue concentrations exceeding those commonly seen with erythromycin. Azithromycin is subsequently slowly released, reflecting its long terminal phase elimination half-life relative to that of erythromycin. These factors allow for a single dose or single daily dose regimen in most infections, with the potential for increased compliance among outpatients where a more frequent antimicrobial regimen might traditionally be indicated. The potential disadvantage of low azithromycin serum concentrations, however, is that breakthrough bacteraemia may occur in patients who are severely ill; nevertheless, animal studies suggest that tissue concentrations of azithromycin are more important than those in serum when treating respiratory and other infections. The clinical efficacy of azithromycin has been confirmed in the treatment of infections of the lower and upper respiratory tracts (the latter including paediatric patients), skin and soft tissues (again including paediatric patients), in uncomplicated urethritis/cervicitis associated with N. gonorrhoeae, Chlamydia trachomatis or U. urealyticum and in the treatment of early Lyme disease. Azithromycin was as effective as erythromycin and other commonly used drugs including clarithromycin, beta-lactams (penicillins and cephalosporins), and quinolone and tetracycline antibiotics in some of the above infections. Some patients with acute exacerbations of chronic bronchitis due to H. influenzae may be refractory to therapy with azithromycin (as is the case with erythromycin) indicating the need for physician vigilance, although it should be noted that azithromycin is of equivalent efficacy to amoxicillin in the treatment of such patients. In the therapy of urethritis/cervicitis associated with C. trachomatis, N. gonorrhoea or U. urealyticum, a single dose azithromycin regimen offers a distinct advantage over currently available pharmacological options, while providing effective therapy.(ABSTRACT TRUNCATED AT 400 WORDS)

Activities of various quinolone antibiotics against Mycobacterium leprae in infected mice

Previously, pefloxacin and ofloxacin were found to be active against Mycobacterium leprae in vitro, in experimental animals, and in clinical trials of lepromatous leprosy patients. In this study, we compared certain more recently developed fluoroquinolones (lomefloxacin, PD 124816, WIN 57273, temafloxacin, and sparfloxacin) with pefloxacin and ofloxacin in M. leprae-infected mice at doses of 50, 150, and 300 mg/kg given five times weekly. All seven of the fluoroquinolones studies were active against M. leprae; temafloxacin and sparfloxacin were the most active, being fully bactericidal at all three dosage schedules. Additionally, sparfloxacin was found to be fully bactericidal at 15 and 30 mg/kg given five times weekly.

Clarithromycin. A review of its antimicrobial activity, pharmacokinetic properties and therapeutic potential

Clarithromycin is an acid-stable orally administered macrolide antimicrobial drug, structurally related to erythromycin. It has a broad spectrum of antimicrobial activity, similar to that of erythromycin and inhibits a range of Gram-positive and Gram-negative organisms, atypical pathogens and some anaerobes. Significantly, clarithromycin demonstrates greater in vitro activity than erythromycin against certain pathogens including Bacteroides melaninogenicus, Chlamydia pneumoniae, Chlamydia trachomatis, Mycobacterium chelonae subspecies--chelonae and--abscessus, Mycobacterium leprae, Mycobacterium marinum, Mycobacterium avium complex, Legionella spp. and, when combined with its 14-hydroxy metabolite, against Haemophilus influenzae. However, bacterial strains resistant to erythromycin are also generally resistant to clarithromycin. The antimicrobial activity of clarithromycin appears to be enhanced by the formation in vivo of the microbiologically active 14-hydroxy metabolite. In combination, additive or synergistic activity against a variety of pathogens including Haemophilus influenzae, Moraxella catarrhalis, Legionella species (principally Legionella pneumophila) and various staphylococci and streptococci has been demonstrated. Clarithromycin has a superior pharmacokinetic profile to that of erythromycin, allowing the benefits of twice daily administration with the potential for increased compliance among outpatients where a more frequent regimen for erythromycin might otherwise be indicated. The clinical efficacy of clarithromycin has been confirmed in the treatment of infections of the lower and upper respiratory tracts (including those associated with atypical pathogens), skin/soft tissues, and in paediatrics. Clarithromycin was as effective as erythromycin and other appropriate drugs including beta-lactams (penicillins and cephalosporins) in some of the above infections. A most promising indication for clarithromycin appears to be in the treatment of immunocompromised patients infected with M. avium complex, M. chelonae sp. and Toxoplasma sp. Small initial trials in this setting reveal clarithromycin alone or in combination with other antimicrobials to be effective in the eradication or amelioration of these infections. Noncomparative studies have provided preliminary evidence for the effectiveness of clarithromycin in the treatment of infections of the urogenital tract, oromaxillofacial and ophthalmic areas. However, the promising in vitro and preliminary in vivo activity of clarithromycin against Mycobacterium leprae and Helicobacter pylori warrant further clinical trials to assess its efficacy in patients with these infections. Despite the improved pharmacokinetic profile and in vitro antimicrobial activity of clarithromycin over erythromycin, comparative studies of patients with community-acquired infections reveal the 2 drugs to be of equivalent efficacy. However, clarithromycin demonstrates greater tolerability, principally by inducing fewer gastrointestinal disturbances.(ABSTRACT TRUNCATED AT 400 WORDS)