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Azithromycin and clarithromycin are two relatively new macrolide antimicrobial agents. Although azithromycin and clarithromycin are structural analogues of erythromycin, they offer distinct advantages in comparison. This article reviews the pharmacokinetics, antimicrobial activity, clinical use, and adverse affects of these antimicrobial agents.
Antimycobacterial drugs acting efficiently against Mycobacterium avium complex have in common low MICs and MBC/MIC ratios. The recently reported clinical efficacy of some of the newer drugs is also clearly linked to their pharmacokinetic properties such as higher serum level and/or intracellular concentrations and half-life. In the present investigation, comparative postantibiotic effects (PAEs) of amikacin, rifampin, sparfloxacin, clofazimine and clarithromycin were investigated. Bacteria were exposed to MIC, MIC x 4 and MIC x 8 concentrations of each drug for 2 h, the drug was removed by centrifugation and cells were thoroughly washed and resuspended in drug-free medium. Growth was compared to control organisms which underwent a similar treatment (but without drugs) and PAEs were assessed using the equation "T-C", where T equals the time required for colony counts to increase by 1 log10 in test samples after antibiotic exposure and C equals the time for 1 log10 growth in control. Our results underlined two distinct patterns concerning PAE: pattern I included drugs for which PAE (in hours) was dose-dependent and varied (for MIC, MIC x 4 and MIC x 8 concentrations) for amikacin (10.3 +/- 1.7, 14.7 +/- 1.9 and 17.7 +/- 4.1), rifampin (28.0 +/- 7.6, 62.0 +/- 18.5 and 71.0 +/- 3.2) and clarithromycin (2.6 +/- 1.0, 15.0 +/- 4.0 and 22.0 +/- 4.0), whereas pattern II included drugs with a stable PAE, relatively independent of the drug concentrations: sparfloxacin (11.0 +/- 2.5, 12.3 +/- 6.4 and 13.0 +/- 2.1) and clofazimine (26.0 +/- 2.8, 28.8 +/- 2.5 and 27.3 +/- 1.3). These results may be useful for guidance in scheduling of drug administration in M. avium-infected AIDS patients overburdened with too many drugs given for various opportunistic infections.
The antimicrobial activities of levofloxacin, clarithromycin and KRM-1648 against Mycobacterium tuberculosis (MTB) and Mycobacterium avium complex (MAC) residing in Mono Mac 6 human macrophage-like cells (MM6-Mphis) and A-549 human type II alveolar epithelial cells (A-549 cells) were studied. We measured the antimicrobial activity of test drugs in terms of effects on the behaviour of intracellular organisms during a 7-day cultivation of MTB- or MAC-infected cells in the medium containing the drugs at Cmax doses. Microbicidal action of levofloxacin against intracellular MTB within A-549 cells was markedly less than its activity against the same organisms in MM6-Mphis. The same effect was also noted for the action of KRM-1648 against MAC organisms but this did not occur with clarithromycin. The MIC of KRM-1648 for MAC multiplying within A-549 cells was 32 times larger than that for MAC residing in MM6-Mphis. These findings indicate that MTB and MAC organisms replicating in the type II lung epithelial cells resist the action of certain antimycobacterial agents such as quinolones and rifamycin derivatives but not when the organisms are contained in macrophages. It appears that the antimicrobial action of certain drugs against intracellular mycobacteria is differentially manifested depending on the types of host cells, i.e. professional phagocytes (MM6-Mphis) or non-professional phagocytes (A-549cells), in which the organisms are contained.
Serum bactericidal activity was studied in a crossover manner in 10 volunteers, after 2-day administration of grepafloxacin 600 mg qd, ofloxacin 400 mg bid and clarithromycin 500 mg bid. Bactericidal activity against clinical isolates of Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis and Klebsiella pneumoniae, was estimated using a standardized microdilution method. Grepafloxacin was highly active against Gram-negative organisms and adequate against pneumococci (mean, 1:13.3). Clarithromycin was very active against both penicillin-susceptible and penicillin-partially-resistant S. pneumoniae (1:102.5) but had poor activity against H. influenzae (1:3.1). Minor adverse effects were commonly associated with grepafloxacin.
The aim of this study was to determine the prevalence of antimicrobial resistance amongst Helicobacter pylori isolates cultured from gastric biopsies taken during routine endoscopies at the American University of Beirut Medical Center in Lebanon. Fifty-four consecutively recovered H. pylori isolates were tested against metronidazole, clarithromycin, tetracycline and amoxycillin using the epsilometer test. Resistance to metronidazole (MIC > 8 mg/l) was found in 29.5% of the isolates while resistance to clarithromycin (MIC > or =0.25 mg/l) and tetracycline (MIC > or =4 mg/l) was low (4 and 2%, respectively). All isolates were susceptible to amoxycillin (MIC < or =8 mg/l). These findings are comparable with those reported from Europe and the United States. The prevalence of metronidazole resistance in our study was lower than that from other parts of the Middle East and the developing world.
The in vitro activity of erythromycin and clarithromycin (a new macrolide antibiotic) on clinical bacterial isolates as well as their effects on the cellular and humoral immune responses in BALB/c-mice and on human granulocytes/monocytes was investigated. Treatment of BALB/c-mice for 7 days with these drugs did not influence the delayed type hypersensitivity to oxazolone nor the production of IgG and IgM immunoglobulins. In vitro, exposure of granulocytes to erythromycin resulted in increased phagocytosis only in higher concentrations (20 mcg/ml), whereas clarithromycin enhanced chemiluminescence response of granulocytes in concentrations ranging from 2.5-20 mcg/ml. Subinhibitory concentrations of both substances modified Staphylococcus aureus and made them more susceptible for granulocyte phagocytosis.
Atypical mycobacterial infections are frequently associated with chronic cervical lymphadenopathy, particularly in children between 1 and 5 years of age. The treatment of choice is regarded to be "optimal" surgical treatment, which often requires wide excision of affected lymph nodes. Although surgical excision is a reliable treatment, it has obvious drawbacks. Because branches of the peripheral facial nerve may be intimately involved in the inflammatory reaction, damage is a potential complication. In addition, keloid scars and wound breakdown are possible complications. Successful drug treatment is hampered by poor susceptibility of the Mycobacterium avium-intracellulare and Mycobacterium scrofulaceum strains to antimicrobial drugs. Reports of results with clarithromycin in the treatment of patients with AIDS who are infected with the M avium complex, however, are promising. The cases of 2 children with infections caused by the M avium complex, resulting in preauricular and cervical lymphadenitis, are described. Treatment with clarithromycin as a monotherapy led to complete healing without recurrence.
BACKGROUND: Crohn's disease, an inflammatory bowel disease in humans, has a suspected aetiology of Mycobacterium avium subsp. Paratuberculosis. AIMS: To evaluate the role of rifabutin and clarithromycin anti-Mycobacterium avium subsp. Paratuberculosis treatment in Crohn's disease patients using an open clinical trial. METHODS: . A total of 36 patients with acute presentations of Crohn's disease, whose sera tested positive against p35 and p36 antigens (two recombinant proteins of Mycobacterium avium subsp. Paratuberculosis), were selected for treatment with rifabutin and macrolide antibiotic therapy Rifabutin and macrolide antibiotic therapy medications included 250 mg 1 po bid clarithromycin and 150 mg 1 po bid Ri-fabutin accompanied with a probiotic. Crohn's disease patients' response to rifabutin and macrolide antibiotic therapy was monitored over a period ranging from 4 to 17 months. RESULTS: Seven patients (19.4%) withdrew from the study since they were unable to tolerate medications. Of the remaining 29 patients, 21 (58.3%) reached a sustained state of improvement, traditionally defined as a decrease of 70 points between their entrance and exit Crohn's disease activity index scores together with the absence of the need of all other Crohn's medications, such as immunosuppressants and corticosteroids. Three Crohn's disease patients [8. 3%) noticed significant improvements, but required other Crohn's medications, concurrently with rifabutin and macrolide antibiotic therapy, to achieve and sustain improvement. Only 5 Crohn's disease patients (13.8%) were non-responders, noticing no marked improvement while on rifabutin and macrolide antibiotic therapy. CONCLUSION: The data add further evidence to support the role of rifabutin and macrolide antibiotic therapy in the treatment of Crohn's disease specifically in those patients with evidence of Mycobacterium avium subsp. Paratuberculosis infection. A large multi-centre clinical trial is needed to further explore these findings.
Microgram levels of clarithromycin residues on various surfaces are quantitated. After cleaning, any residual clarithromycin remaining is removed from the surface by a wet swab-dry swab technique. High-performance liquid chromatography with electrochemical detection is used for quantitation of the resulting solutions. Recoveries ranged from 93 to 118%.
Peptide libraries displayed by T7 phage, which contain random cDNA fragments insets, were screened for their ability to bind to a biotinylated derivative of clarithromycin. Phage particles bound to an immobilized derivative of the antibiotic were isolated and the inserted cDNA was amplified and sequenced. A common selected peptide sequence, composed of 19 amino acids, was obtained and a synthetic peptide with this sequence was produced. Surface plasmon resonance experiments showed that the synthetic peptide immobilized on a sensor chip bound to clarithromycin and the dissociation constant was determined to be 2.1 x 10(-3) M. The dissociation constants of other macrolide antibiotics, erythromycin, roxithromycin, azithromycin and josamycin were also determined to be 5.4 x 10(-3) M, 6.2 x 10(-5) M, 1.1 M and 3.4 x 10(-2) M, respectively. These results indicated that T7 phage display method might be useful to determine relatively weak interactions between small molecule drugs and the selected peptides which could represent a possible binding site conserved in binding proteins.
BACKGROUND: Triple therapy with omeprazole, clarithromycin, and tinidazole (OCT) has been found to be highly effective against Helicobacter pylori infection. However, its efficacy as a second line regimen for patients who failed metronidazole-based triple therapy has not been evaluated. AIM: The aim of this study was to evaluate the efficacy of low-dose, short-term OCT therapy in an Israeli population, and to compare results obtained in previously treated and untreated patients. METHODS: Patients with duodenal or gastric ulcers and chronic antral gastritis with H. pylori infection as assessed by rapid urease test and/or 14C urea breath test (14C-UBT), were studied. All patients received omeprazole 20 mg b.d., clarithromycin 250 mg b.d. and tinidazole 500 mg b.d. for 7 days. Eradication was assessed by 14C-UBT 4 weeks after treatment. RESULTS: One hundred and fourty-four patients (M/F = 81/63) were enrolled (mean age 48.1 years, range 12-78). Eradication of H. pylori was significantly different between patients who were initially treated with this regimen (90/94, 96%) and patients who had previously failed to eradicate H. pylori with standard triple therapy (27/50, 54%). Moreover, the eradication rate was significantly decreased in patients with more than one previous failure (9/22, 41%) compared to that in patients with only one failure (18/29, 62%). No other differences such as age, gastric pathology, ethnic origin, smoking habits, or pre-treatment urease activity were found to influence the eradication rate. CONCLUSIONS: One-week low-dose triple therapy with OCT is highly effective as an initial therapy in eradicating H. pylori infection. The efficacy is significantly lower when given as a second line treatment in patients who have previously failed to eradicate H. pylori with bismuth-based standard triple therapy.
AIM: To evaluate and compare two 1-week low-dose triple therapies based on lansoprazole, amoxycillin and a macrolide in eradicating Helicobacter pylori. METHODS: Seventy consecutive patients, suffering from dyspeptic symptoms with H. pylori infection, were randomly allocated to one of two treatment groups: (A) (LAC; n = 35) lansoprazole 30 mg once daily, amoxycillin 1000 mg b.d., clarithromycin 250 mg b.d., all for 7 days; and (B) (LAA; n = 35) lansoprazole 30 mg once daily and amoxycillin 1000 mg b.d., both for 7 days, plus azithromycin 500 mg once daily for only 3 days. The H. pylori status was evaluated by means of histology and rapid urease test at entry and 8 weeks after treatment. RESULTS: Three patients did not complete the treatment: one in the LAC group was withdrawn owing to severe side-effects; two patients in the LAA group stopped the treatment prematurely. H. pylori eradication was obtained in 28 of 34 (82%; 95% CI = 66-93%) patients in the LAC group and in 20 of 33 (61%; 95% CI = 42-77%) patients in the LAA group. The difference is significant (P < 0.029). On intention-to-treat analysis, the rates of eradication were (28 of 35 patients, 80% in the LAC group and 20 of 35 patients, 57% in the LAA group. Side-effects occurred in nine (26%) and six (18%) patients in the LAC and LAA groups, respectively. CONCLUSIONS: Low-dose lansoprazole plus amoxycillin and clarithromycin is more effective than low-dose lansoprazole plus amoxycillin and azithromycin, but it gave a greater incidence of side-effects.
BACKGROUND: The efficacy of H2-antagonists in combination with antibiotics in curing Helicobacter pylori infection remains controversial, and it is uncertain whether double dose H2-antagonist therapy is superior to standard dose. AIM: To determine the efficacy of two doses of nizatidine in combination with two antibiotics in the treatment of H. pylori. METHODS: A randomized controlled trial was conducted in 160 patients comparing nizatidine 150 mg with 300 mg b.d. (standard vs. double dose), in combination with clarithromycin (500 mg) and amoxycillin (1000 mg) b.d. for 14 days, in Australia and Taiwan. Compliance was based on a clinical assessment and pill count. H. pylori status was determined by histology (antrum and corpus) and CLO-test. RESULTS: Baseline clinical and endoscopic findings were similar in both arms of the study. Based on an intention-to-treat analysis, cure of H. pylori was achieved in 78% (95% CI: 70.4-85.4%) in the standard nizatidine dose arm and 70% (95% CI: 61.6-78.2%) in the double dose arm (P=0.2). Similar cure rates were observed in ulcer and non-ulcer patient groups. Compliance was excellent in the single and double dose arms (85 and 91%, respectively). CONCLUSIONS: The combination of nizatidine in standard or double dose with clarithromycin and amoxycillin is similarly efficacious in curing H. pylori infection.
BACKGROUND: A number of triple drug regimens using proton pump inhibitors and two antibiotics have been evaluated in the West and reported to achieve Helicobacter pylori eradication rates of over 90%. In developing countries however, these combinations have neither been well evaluated, nor the optimum treatment for H. pylori infection well defined. AIM: To compare the combination of a proton pump inhibitor with a nitroimidazole and another antibiotic in eradicating H. pylori infection and healing duodenal ulcer. METHODS: Sixty consecutive patients with active duodenal ulcer who were positive for H. pylori (by rapid urease test and 14C-urea breath test) were randomized into three treatments groups: (1) LAS (n=21): lansoprazole 30 mg o.m., amoxycillin 500 mg q.d.s. and secnidazole 2 g on alternate days for 2 weeks; (2) LCS (n=18): lansoprazole 30 mg o.m., clarithromycin 500 mg b.d. and secnidazole 2 g on alternate days for 1 week; (3) LPS (n=21): lansoprazole 30 mg o.m., pefloxacin 400 mg o.m. and secnidazole 2 g on alternate days for 2 weeks. Urease and breath tests were performed at 0, 6 and 12 weeks to check for H. pylori eradication. RESULTS: Intention-to-treat eradication rates were as follows: LAS 86%, LCS 83%, LPS 71%; the overall ulcer healing rate was 90% at 6 weeks. CONCLUSIONS: High H. pylori eradication rates were achieved using the amoxycillin- and clarithromycin-based therapies. Fewer side-effects, better compliance and low cost favoured the amoxycillin-based therapy.
BACKGROUND: Experience with proton pump inhibitor-based triple therapy is predominantly with omeprazole-containing regimens. AIM: To investigate the efficacy of a pantoprazole-based regimen, with either a 1 or 2-week course of antibiotic co-therapy, in eradicating H. pylori, healing duodenal ulcers and to assess the antibiotic sensitivity profiles of isolated H. pylori strains. METHODS: A single-blind, multicentre, parallel group comparison of patients with endoscopically proven, H. pylori associated, active duodenal ulceration. All patients received pantoprazole, 40 mg b.d. for 2 weeks. Patients were randomized to receive either 1 or 2 weeks of therapy with amoxycillin, 1 g b.d. and clarithromycin 500 mg b.d. Patients were endoscoped at entry, at 14 days and a minimum of 4 weeks after cessation of all therapy. H. pylori status was determined by urease reaction, histological assessment and culture from antral and body biopsies. Antibiotic sensitivity was determined using the agar dilution technique. RESULTS: Sixty-seven patients were randomized. One week co-therapy (n=33): eradication efficacy, ITT= 79% (95% CI: 61-91%); ulcer healing efficacy (at 6-week visit)=88% (95% CI: 72-97%). Two-week co-therapy (n=34): eradication efficacy, ITT=91% (95% CI: 76-98%: ulcer healing efficacy= 88% (95% CI: 73-97%). Both regimens were well tolerated and no primary antibiotic resistance was noted. CONCLUSION: Pantoprazole-based triple therapy, with either 1 or 2 weeks of co-therapy with amoxycillin and clarithromycin, is effective in eradicating H. pylori and healing duodenal ulceration.
BACKGROUND: Ranitidine bismuth citrate (RBC) co-prescribed with clarithromycin and metronidazole for 1 week has been shown to be an effective eradicating regimen for Helicobacter pylori. AIM: To determine the optimal duration of this regimen. METHODS: A series of 165 dyspeptic patients were recruited for this randomized, open, parallel-group study. They were subdivided into three groups receiving RBC 400 mg b.d. plus clarithromycin 250 mg b.d. and metronidazole 500 mg b.d. for three different periods (4, 7 and 10 days). H. pylori infection was assessed by the concomitant positivity of CLO-test and histology performed at the pre-entry endoscopy. The bacterium was considered eradicated on the basis of a negative 13C-urea breath test performed at least 28 days after the completion of treatment. RESULTS: The three subgroups were well matched and 16 patients dropped out of the study for many reasons (six in the 4-day, five in the 7-day and five in the 10-day treatment regimens). Intention-to-treat cure rates were 60%, 84% and 85%, and the per-protocol rates 67%, 92% and 94% in the 4-day, 7-day and 10-day treatment regimens, respectively. There was a significant difference, P = 0.003-0.006 on intention-to-treat and P = 0.001-0. 002 on per protocol analysis between the 4-day and the 7-day and the 4-day and the 10-day periods, respectively. The 7-day and 10-day periods did not differ from each other. Side-effects were reported in 9%, 14% and 20% of the 4-, 7- and 10-day regimens. They led to stopping treatment in four cases (one in the 7-day and three in the 10-day period). There was no statistical difference among them. CONCLUSIONS: Reducing the duration of RBC-based triple therapy to 4 days provides a low and unacceptable rate of H. pylori eradication. As there is no difference between 7 and 10 days of treatment, 1 week represents the optimal time period for this kind of treatment, based on RBC plus two antibiotics.
BACKGROUND: The impact of metronidazole resistance on the efficacy of proton pump inhibitor based triple therapies remains unclear. AIM: To study whether metronidazole resistance affects Helicobacter pylori eradication rates in patients treated for 1 week with either omeprazole 20 mg b.d., metronidazole 400 mg b.d. and clarithromycin 250 mg b.d. (OMC), or omeprazole 20 mg b.d., amoxycillin 1000 mg b.d. and clarithromycin 500 mg b.d. (OAC). METHODS: A randomized, single blind, single centre study with parallel groups was conducted. H. pylori positive patients were enrolled in a metronidazole-resistant (MR; MIC > 8 microgram/mL) or a metronidazole-susceptible group (MS; MIC < 4 microgram/mL), as determined by E-test. Within the strata patients were randomized to either OAC or OMC. RESULTS: One hundred and twenty-two patients were included. The per protocol cure rate for OAC was 52 out of 57 (91%) (MS 23 out of 26 (89%); MR 29 out of 31 (94%)) and for OMC 46 out of 55 (84%) (MS 19 out of 22 (86%); MR 27 out of 33 (82%)). CONCLUSIONS: One-week OAC and OMC are effective therapies. OAC and OMC were equally effective in patients with metronidazole-susceptible strains of H. pylori. Using the OMC regimen, neither equality nor significant differences in treatment outcome could be shown between patients with metronidazole-resistant or -susceptible strains of H. pylori.
BACKGROUND: Ranitidine bismuth citrate (RBC)-based triple therapies for a period of 7 days have proved to be an effective treatment for Helicobacter pylori. AIM: To investigate the eradication efficacy, safety profile and patient compliance of two RBC-based triple therapies given for 5 days. METHODS: Eighty H. pylori-positive patients with dyspeptic symptoms, referred to us for gastroscopy, were consecutively enrolled in this prospective, randomized, open-label study. These patients were randomly assigned to receive a 5-day course of RBC 400 mg b.d. plus clarithromycin 500 mg b.d. and either tinidazole 500 mg b.d. (RBCCT group) or amoxycillin 1 g b.d. (RBCCA group). The H. pylori status was assessed by means of histology and rapid urease test at entry, and by 13C-urea breath test 8 weeks after the completion of treatment. RESULTS: All enrolled patients completed the study. Thirty-seven of 40 patients treated with RBCCT (both PP and ITT analysis: 93%; 95% CI: 80-98%) and 35 of 40 in the RBCCA group (both PP and ITT analysis: 88%; 95% CI: 73-96%) returned H. pylori-negative. Slight or mild side-effects occurred in 4/40 patients (10%) in the RBCCT group and in 5/40 (12%) in the RBCCA group. CONCLUSIONS: This is the first study demonstrating the efficacy of RBC-based triple therapies given for only 5 days. RBC regimens containing high-dose clarithromycin and either amoxycillin or tinidazole prove to be well tolerated, safe and preserve good eradication rates even when administered for a shorter than conventional duration.