Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0348321 (Haemophilus)
 15,372 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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)
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PMID:Azithromycin. A review of its antimicrobial activity, pharmacokinetic properties and clinical efficacy. 128 May 67

Upper and lower respiratory tract infections are the most frequently reported pathologies both in children and in adults. In particular, the most common clinical pictures are otitis media, principally chronic, and acute and chronic sinusitis. The microbiology of otitis media, which has been investigated thoroughly in the last year, confirmed a bacterial origin in 90% of the cases (while the incidence of the viral form is low). The etiologic agents responsible for chronic infections are Gram-negative bacteria, staphylococci and anaerobic bacteria, while in the acute forms, which are rare in adults but frequent in children, the responsible pathogens are principally Haemophilus influenzae, Streptococcus pyogenes and Branhamella catarrhalis. Among the etiologic agents of chronic sinusitis, which, from a clinical point of view, is the most frequently observed, there are staphylococci, Streptococcus pyogenes and many anaerobic bacteria. As regards lower respiratory tract infections, chronic bronchitis is the most frequent pathology in adults. But, in this case, the etiologic agents are more difficult to identify. Analysing the above-mentioned clinical pictures and their relevant etiologic agents, among the different therapeutic proposals, one of the most innovative and recent is represented by azithromycin. Azithromycin is the first of a new class of macrolides termed "Azalides" which shows particular microbiological and pharmacokinetic characteristics. As compared to other macrolides, it has an higher distribution volume, a longer half-life, a deeper intracellular penetration and a wider spectrum of action. It is rapidly concentrated in leukocytes PMN, monocytes, macrophages and fibroblasts and slowly released by these cells to the infected tissues. Azithromycin concentrations in tissues and sites of infection can be increased by the phagocyte uptake.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[The etiology of bacterial respiratory infections in adulthood]. 129 1

The chemistry, mechanism of action, antimicrobial spectrum, pharmacokinetics, clinical efficacy, adverse effects, drug interactions, and dosage and administration of clarithromycin and azithromycin are described. Clarithromycin and azithromycin are new macrolide antibiotics that are similar in structure to erythromycin. Compared with erythromycin, clarithromycin demonstrates increased activity against Staphylococcus aureus, streptococci, Legionella pneumophila, Moraxella catarrhalis, and Chlamydia trachomatis. Clarithromycin also has in vitro activity against Mycobacterium avium complex (MAC) and Toxoplasma gondii. Azithromycin has increased gram-negative activity compared with erythromycin, including activity against Haemophilus influenzae, while maintaining activity against gram-positive organisms. Azithromycin also has activity against sexually transmitted organisms including Chlamydia trachomatis. The pharmacokinetic profiles of clarithromycin and azithromycin are characterized by good oral bioavailability, excellent tissue penetration and persistence, and long elimination half-lives, which allow for once-daily or twice-daily dosing. Initial data show that clarithromycin and azithromycin are effective for the treatment of upper-respiratory-tract and lower-respiratory-tract infections and infections of the skin and skin structures. Azithromycin has been shown to be effective for the treatment of sexually transmitted diseases caused by Chlamydia trachomatis. Clarithromycin and azithromycin have been used to treat MAC and Toxoplasma infections in patients with the acquired immunodeficiency syndrome. The most frequently reported adverse effects for both agents have been nausea, diarrhea, and abdominal pain. Oral formulations of clarithromycin and azithromycin have recently been approved by the FDA. Clarithromycin and azithromycin are new macrolide antibiotics that have potential advantages over erythromycin; however, the role of these agents will be better defined as results of more ongoing trials become available for evaluation.
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PMID:Clarithromycin and azithromycin: new macrolide antibiotics. 151 40

Azithromycin is an azalide antimicrobial agent. Structurally related to the macrolide antibiotic erythromycin, its mechanism of activity (similar to erythromycin) is interference with bacterial protein synthesis by binding to the 50S component of the 70S ribosomal subunit. Although slightly less potent than erythromycin against gram-positive organisms, azithromycin demonstrates superior activity in vitro against a wide variety of gram-negative bacilli, including Haemophilus influenzae. Absorption is approximately 37% after a 500-mg oral dose. The large volume of distribution (23 L/kg) and low peak serum level (0.4 micrograms/ml) are consistent with data demonstrating extensive tissue distribution and intracellular accumulation. Metabolism is predominantly hepatic (to inactive metabolites), with biliary excretion a major pathway of elimination. Drug elimination is biphasic, with a terminal half-life of up to 5 days. Published trials have examined the efficacy and safety of azithromycin in the treatment of adults with upper and lower respiratory tract infections, skin and skin structure infections, streptococcal pharyngitis, and sexually transmitted diseases. Many used a 5-day course of 250 mg once daily, supplemented with a 250-mg dose on the first day of therapy. Selected trials in sexually transmitted diseases examined single 1-g doses. Promising results also were obtained with oral daily doses of 500 mg in patients with human immunoviral infection who also had Mycobacterium avium complex infection and in animals with toxoplasmosis. Adverse reactions are primarily gastrointestinal (nausea, diarrhea, abdominal pain), with minimal laboratory abnormalities reported. Gastrointestinal tolerance is better than that of erythromycin. Drug interactions have not been observed to date, although coadministration of azithromycin with a large meal may reduce absorption by up to 50%.
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PMID:Azithromycin--spectrum of activity, pharmacokinetics, and clinical applications. 131 48

The in vitro susceptibility of Actinobacillus actinomycetemcomitans to azithromycin, a new macrolide antibiotic of a new class known as azalides, was compared with that of erythromycin by the agar dilution method on Mueller-Hinton Haemophilus test medium. Eighty-two A. actinomycetemcomitans strains, 79 recent clinical isolates obtained from 40 periodontally healthy or diseased subjects, and 3 type strains were included in the study. Erythromycin showed poor in vitro activity against A. actinomycetemcomitans. Azithromycin, however, was highly effective against A. actinomycetemcomitans: all strains were inhibited at 2.0 micrograms/ml. Azithromycin exhibited the best in vitro activity against the serotype a subpopulation of A. actinomycetemcomitans: 100% of the strains were inhibited at 1.0 micrograms/ml. The lowest MICs were, however, recorded by serotype b strains. Since azithromycin has favorable pharmacokinetic properties, including excellent distribution into tissues, it could be expected to pass into gingival crevicular fluid at levels sufficient to inhibit A. actinomycetemcomitans in vivo. Therefore, it is a good candidate for future clinical trials in A. actinomycetemcomitans-associated periodontitis.
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PMID:In vitro activity of azithromycin compared with that of erythromycin against Actinobacillus actinomycetemcomitans. 132 17

The accumulation of azithromycin in phagocytic cells was studied both in vitro by using a radiolabelled drug and a bioassay and in vivo for 12 volunteers receiving 1.5 g (total dose) orally within 3 days. In vitro, neutrophils and unfractionated blood leukocytes accumulated azithromycin up to 160-fold the extracellular concentration within 1 h at 37 degrees C but less than 3-fold at 4 degrees C. Dead cells accumulated up to 30-fold azithromycin, whereas NaF-treated cells accumulated up to 60-fold arithromycin. The mean efflux from preloaded cells was at most 31.0% +/- 10.6% (standard error of the mean) of the cell-associated concentration within 4 h of incubation at 37 degrees C in drug-free buffer. In vivo, the azithromycin concentration was 45.2 +/- 6.1 mg/liter of intracellular fluid at 2 h after the third dose and 36.6 +/- 8.3 mg/liter at 1 week thereafter. The corresponding concentrations in serum were 0.2 +/- 0.1 (2 h) and less than 0.05 (1 week). The luminol-enhanced chemiluminescence response induced by phorbol myristate acetate, opsonized zymosan, and two opsonized strains of Haemophilus influenzae (a type b capsulated strain and a noncapsulated strain) was also studied ex vivo by using the blood leukocytes from the 12 test volunteers and 4 control volunteers at 2 and 6 h after the third oral dose of azithromycin and at 2, 4, and 7 days thereafter. Azithromycin did not influence this response despite high levels of cellular accumulation.
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PMID:In vitro and in vivo intraleukocytic accumulation of azithromycin (CP-62, 993) and its influence on ex vivo leukocyte chemiluminescence. 132 19

Azithromycin is a newly developed azalide antibiotic which is very active against microbes causing respiratory tract infections; tissue concentrations remain elevated for a long time after discontinuation of treatment. A clinical study was conducted to compare azithromycin (10 mg/kg administered as a single daily dose for 3 days) with amoxycillin/clavulanic acid (50 mg/kg/day given b.i.d. for 10 days) in 30 children with otitis media. Sensitivity testing demonstrated good azithromycin activity against beta-haemolytic streptococci, Moraxella catarrhalis, Haemophilus influenzae and Staphylococcus aureus. By day 12, clinical cure was recorded in 14/15 children treated with azithromycin and this was maintained at day 30. In the day 12 and 13/15 children by day 30. It was concluded that a 3-day azithromycin regimen produces a satisfactory clinical response and the eradication of key pathogens, and was acceptable for children.
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PMID:Azithromycin in upper respiratory tract infections: a clinical trial in children with otitis media. 133 92

Azithromycin is a new azalide antimicrobial agent which has a broad spectrum of activity against common lower respiratory tract pathogens including pneumococci, staphylococci, Legionella species, Mycoplasma and Chlamydia species. In particular, it is more active against Haemophilus influenzae than other macrolides. In comparison to other new macrolides, azithromycin achieves higher tissue and intracellular concentrations and these concentrations are sustained for several days after dosing due to a long elimination half-life. The efficacy of azithromycin against lower respiratory tract infections has been proven in several clinical studies. Once-daily dosing with azithromycin, over a 3- or 5- day period was as effective as a 10-day course of other commonly used antibiotics such as amoxycillin/clavulanic acid, erythromycin or cefaclor in lower respiratory tract infections. Azithromycin short-course therapy may offer an advantage in terms of patient compliance and the duration of treatment.
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PMID:Azithromycin in lower respiratory tract infections. 133 93

After almost forty years of its introduction, erythromycin will not be the exclusive member of the macrolide group of antibiotic agents, but a new generation of its derivatives which surpass it in pharmacological properties and clinical efficacy will also be available. Clarithromycin, a 14-membered derivative, has shown acid stability, longer half-life, lower protein binding and higher lung tissue penetration. Its exceedingly high activity against erythromycin-susceptible gram-positive cocci, Mycoplasma pneumoniae, and Legionella pneumophila makes it and important alternative choice in the therapy of respiratory tract infections. Also, it has shown high activity against Chlamydia trachomatis, and high urinary clearance of this unmetabolized molecule, important properties which would render it a special role in the treatment of genitourinary tract infections. Azithromycin, a 15-membered derivative has shown enhanced basicity (due to the nitrogen atom in its lactone ring), longer half-life and lower protein bindings. Its exceptional activity against Hemophilus influenzae, Branhamella catarrhalis, Neisseria gonorrhoeae, Ureaplasma urealyticum and gram-negative bacteria, and its high concentration in tonsillar, pulmonary, prostatic and female reproductive tract tissues, assigns it an honorific place among the macrolides in the therapy against respiratory tract and genitourinary tract infections. Its role against T. gondii deserves further study, but points out this agent as a promise against this parasite.
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PMID:The new macrolides: expanding the ways in antibiotic treatment. 150 85

Azithromycin contains an aza-methyl substitution in the 15-membered aglycone ring and as such it is the prototype antibiotic of the azalide class, similar in mechanism of activity to the macrolides. It demonstrates a broad spectrum of activity against many aerobic and anaerobic Gram-positive species, and also inhibits a number of important aerobic and anaerobic Gram-negative bacteria. Significantly, azithromycin shows good activity against Haemophilus influenzae, an organism against which older macrolide antibiotics have proved disappointing. It is highly effective in inhibiting clinically significant intracellular pathogens such as Chlamydia trachomatis and Legionella. Bactericidal activity is seen for certain streptococci and for H. influenzae. Closely linked with azithromycin's microbiologic activity are its novel pharmacokinetics. Azithromycin moves rapidly from blood to tissue compartments where it remains for prolonged periods. Although serum concentrations remain low, the levels attained in the tissues (often greater than 2 mg/kg) are higher than the minimum inhibitory concentration for many common pathogens, and delivery of drug to infection sites by phagocytic cells contributes to these concentrations. This penetration into eukaryotic and prokaryotic cells may be responsible for azithromycin's expanded spectrum of activity, particularly against intracellular organisms. The use of antibiotic blood levels as breakpoints for susceptibility would appear to be inappropriate in the case of azalides. Rather, levels of drug at the tissue site of infection should be considered as guides to predicting efficacy. The in vitro activity of azithromycin, together with its unique tissue pharmacodynamics, define an agent that should demonstrate utility in infections of the respiratory tract, skin and skin structures, and certain sexually transmitted diseases.
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PMID:Clinical microbiology of azithromycin. 165 36


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