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PubMed2006

Pharmacokinetic/pharmacodynamic modeling of in vitro activity of azithromycin against four different bacterial strains.

The bacterial time-kill curves of azithromycin against four bacterial strains (Streptococcus pneumoniae/penicillin-intermediate, S. pneumoniae/penicillin-sensitive, Haemophilus influenzae and Moraxella catarrhalis) were determined by in vitro infection models. Eighteen different pharmacokinetic/pharmacodynamic models were fitted to the time-kill data using non-linear regression and compared for best fit. A simple, widely used E(max) model was not sufficient to describe the pharmacodynamic effects for the four bacterial strains. Appropriate models that gave good curve fits included additional terms for saturation of the number of bacteria (N(max)), delay in the initial bacterial growth phase and/or the onset of anti-infective activity (1-exp(-zt)) as well as a Hill factor (h) that captures the steepness of the concentration-response profile. Azithromycin was highly effective against S. pneumoniae strains and M. catarrhalis while the efficacy against H. influenzae was poor. Applications of these pharmacokinetic/pharmacodynamic models will eventually provide a tool for rational antibiotic dosing regimen decisions.

Anti-Bacterial Agents↗

PubMed2006

The effect of treatment with moxifloxacin or azithromycin on acute bacterial rhinosinusitis in mice.

OBJECTIVE: Acute bacterial rhinosinusitis, which is a major health problem, is treated with antibiotics. We developed a mouse model of acute bacterial rhinosinusitis to gain a better understanding of the pathophysiology of the disease. Our goal was to investigate the response to acute rhinosinusitis when treated with either a bactericidal or a bacteriostatic antibiotic. METHODS: C57BL/6 mice were infected intranasally with Streptococcus pneumoniae. One day after inoculation, the mice were treated with either moxifloxacin (bactericidal) or azithromycin (bacteriostatic). Different groups were euthanized during the first five days post-inoculation. Bacterial counts from nasal lavage culture and the cell markers GR1, CD11b, CD3, CD4, and CD8 in sinus tissue were evaluated by flow cytometry. RESULTS: Azithromycin led to rapid clearance of the bacteria and of the inflammation in contrast to placebo. Surprisingly, moxifloxacin showed a limited effect. Investigations of this limited effect of moxifloxacin suggested a high metabolic clearance, a low concentration at the site of infection, and low persistent post-antibiotic effects of moxifloxacin in mice. CONCLUSION: Our animal model of acute sinusitis has great utility for studying the disease, but the difference between mice and man must always be considered in making extrapolations from animal experiments to the human experience.

Acute Disease↗

PubMed2004

Identification of 5-aminosalicylic acid, ciprofloxacin and azithromycin by abrasive stripping voltammetry.

Solid microparticles of 5-aminosalicylic acid, ciprofloxacin, and azithromycin were mechanically immobilized on the surface of the paraffin impregnated graphite electrode and investigated by square-wave and cyclic voltammetry in order to develop a method for their qualitative determination. 5-Aminosalicylic acid is oxidized at 0.540 V in the quasireversible electrode reaction, which is followed by the chemical transformation of the product, while ciprofloxacin and azithromycin are oxidized at 1.2 V and 0.94 V, respectively, in totally irreversible electrode reactions. The detection of these drugs in commercial dosage formulations is reported.

Azithromycin↗

PubMed2006

Tissue disposition of azithromycin after intravenous and intramuscular administration to rabbits.

Tissue disposition of azithromycin after intravenous (IV) or intramuscular (IM) injection at a single dose rate of 10mg/kg bodyweight were investigated in rabbits using a modified agar diffusion bioassay for determining tissue concentrations. The pharmacokinetic behaviour of azithromycin was characterized by low and sustained plasma concentrations but high and persistent tissue concentrations. Kinetic parameters indicated a high retention of the drug in peripheral compartments. The plasma half-lives after IV and IM administrations were similar being 21.8h and 23.1h, respectively, while the half-lives obtained in tissues after IV and IM administration were at least 1.4 and 1.9 times longer than in plasma, respectively. The highest tissue concentrations were found in bile, liver and spleen whereas the lowest ones were found in skeletal muscle (although they were higher than those in plasma). From the results of the single administration in this study an IM dosage regimen can be proposed that achieves minimum concentrations over 2mg/L in rabbits: three doses of 4-5mg/kg/day would provide suitable therapeutic concentrations in pulmonary tissues over seven days.

Animals↗

PubMed2000

In vivo uptake of azithromycin in human coronary plaques.

Ten patients with symptomatic coronary artery disease received oral azithromycin for 3 days and underwent directional atherectomy on the third day. Azithromycin was found in all plaque samples with a median concentration of 284 ng/ml (95% confidence interval 163 to 517 ng/ml).

Anti-Bacterial Agents↗

PubMed1994

Presence of azithromycin breast milk concentrations: a case report.

We describe a case of breast milk concentrations of azithromycin, an azalide antibiotic, in a woman with postpartum bilateral tubal ligation incisional cellulitis. Azithromycin appears to demonstrate a time-dependent versus time-accumulation profile in breast milk.

Adult↗

PubMed1993

Azithromycin for treatment of severe Cryptosporidium diarrhea in two children with cancer.

Two children with cancer received azithromycin for Cryptosporidium-associated diarrhea that was unresponsive to supportive care. One child had choleriform diarrhea requiring daily fluid replacement of up to 65% of his total body weight; the other had protracted diarrhea and wasting. In both cases, administration of azithromycin was followed by prompt clinical improvement.

Administration, Oral↗

PubMed2000

The newer macrolides: azithromycin and clarithromycin.

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.

Anti-Bacterial Agents↗

PubMed2002

Disposition and intracellular activity of azithromycin in human THP-1 acute monocytes.

Uptake of [14C]-azithromycin into THP-1 human monocytes was determined at pH 7.4, 6.8 or 5.5 over 4-log antibiotic concentrations for 24 h under a number of conditions. Stimulation of cells was with bacteria, latex beads, lipopolysaccharide (LPS), or zymogen A. Subcellular organelle disposition was determined after isolation by ultracentrifugation or sucrose gradients. Hydrolytic enzyme activities and mediators of intracellular inflammation (IL-1, IL-6, IL-8, and TNFalpha) were assessed. Azithromycin uptake into human THP-1 monocytes was initially linear achieving approximately 2% of the extracellular concentration. At pH 7.4, uptake was both passive- and carrier-mediated, but as the pH became more acidic, the uptake was exclusively passive. The intracellular concentration was not pH-dependent over 24 h. Uptake was dependent upon temperature but not the presence of foetal calf serum. Intracellular disposition in zymogen A-stimulated and unstimulated cells was throughout all compartments of the cell, but was higher in the nucleus and cell sap. Phagosomes of stimulated cells contained higher level of the antibiotic. Efflux from THP-1 monocytes was complete between 3 and 4 h. After 1 h treatment with zymogen A, THP-1 monocytes demonstrated an increase in intracellular acidity, protein kinase C, SOD and NAG activities, and NO, H(2)O(2), TNFalpha and IL-1 release over the 1st h. After 2-4 h the pH became alkaline, activities of NADPH reductase, NAG and cathepsin were reduced, and the release of NO, H(2)O(2), TNFalpha and IL-6 were suppressed. Protein synthesis and killing of the bacteria was evident in bacteria kept in monocyte-free medium and those phagocytized by the THP-1 monocytes moderately at 2 h, but more significantly at 24 h. The early killing of the bacteria appears to be a cidal mechanism whereas later, a standard bacteriostatic mechanism was evident. Nevertheless, suppression of these chemical mediators and hydrolytic enzyme activities would reduce the infection and the spread to adjacent areas.

Anti-Bacterial Agents↗

PubMed2003

Comparative analysis of azithromycin and ciprofloxacin in the treatment of chronic prostatitis caused by Chlamydia trachomatis.

A total of 89 patients, (>18 years), with symptoms of chronic prostatitis and inflammatory findings as well as the presence of Chlamydia trachomatis confirmed by DNA/RNA DIGENE hybridization method and/or by isolation, McCoy culture and Lugol stain in expressed prostatic secretion or in voided bladder urine collected immediately after prostatic massage, were examined. The patients were randomized to receive a total of 4.5 g of azithromycin for 3 weeks, given as a 3-day therapy of 1 x 500 mg weekly or ciprofloxacin 500 mg b.i.d. for 20 days. Patients' sexual partners were treated at the same time. Clinical and bacteriological efficacy were evaluated 4-6 weeks after the end of therapy. Significantly higher eradication (36/45: 17/44; P=0.0002) and a significantly higher clinical cure (31/45: 15/44; P=0.0021) were achieved in the group of patients treated with azithromycin than in the ciprofloxacin group.

Adolescent↗

PubMed2002

Characterization of azithromycin hydrates.

Azithromycin (AZI) is a macrolide antibiotic with an expanded spectrum of activity that is commercially available as a dihydrate. This study was carried out to characterize hydrates of azithromycin. A commercial dihydrate sample was used to prepare monohydrate from water/ethanol (1:1) mixture. Hydrates were characterized using DSC, TGA, KFT, XRD, HSM, SEM and FT-IR. TGA showed that the commercial samples are dihydrate and the sample prepared from water/ethanol (1:1) was a monohydrate. Solubility studies revealed that monohydrate converted to dihydrate during solubility studies and as a result there was no significant difference in the equilibrium solubility of MH and DH. Thermal analysis under various conditions revealed that dehydration and melting took place simultaneously. Anhydrous AZI was found to be hygroscopic and converted to DH on storing at room temperature. Molecular modeling studies revealed the probable sites of attachment of water molecules to AZI.

Azithromycin↗

PubMed2003

Cell handling, membrane-binding properties, and membrane-penetration modeling approaches of pivampicillin and phthalimidomethylampicillin, two basic esters of ampicillin, in comparison with chloroquine and azithromycin.

PURPOSE: The purpose of this work was to examine and understand the cellular pharmacokinetics of two basic esters of ampicillin, pivaloyloxymethyl (PIVA) and phthalimidomethyl (PIMA), in comparison with lysosomotropic drugs (chloroquine, azithromycin). METHODS: Cell culture studies (J774 macrophages) were undertaken to study uptake and release kinetics and to assess the influence of concentration, pH, proton ionophore (monensin), and MRP and P-gp inhibitors (probenecid, gemfibrozil, cyclosporin A, GF 120918). Equilibrium dialysis with liposomes were performed to directly asses the extent of drug binding to bilayers. Conformational analysis modeling of the drug penetration in bilayers was conducted to rationalize the experimental observations. RESULTS: PIVA and PIMA showed properties in almost complete contrast with those of chloroquine and azithromycin, i.e., fast apparent accumulation and fast release at 4 degrees C as well as at 37 degrees C, saturation of uptake (apparent Kd 40 microM), no influence of monensin, MRP, or P-gp inhibitors; tight binding to liposomes (Kd approx. 40 microM); and sharp increase in calculated free energy when forced in the hydrophobic domain. CONCLUSIONS: Although they are weak organic bases, PIVA and PIMA show none of the properties of lysosomotropic agents. We hypothesize that they remain locked onto the pericellular membrane and may never penetrate cells as such in significant amounts.

Ampicillin↗

PubMed2004

Theoretical study of selective methylation in the synthesis of azithromycin.

Azithromycin is a 15-membered macrolide antibiotic which is active in vitro against clinically important gram-negative bacteria. In this study, the selectivity of the methylation mechanism was analyzed computationally on the 2'-OCbz-3'-NMeCbz derivative of azithromycin in vacuum and in DMF. We have shown that the methylation of the hydroxy group on C-6 is energetically unfavorable compared to the other hydroxy groups in vacuum; the softness values further showed that the C-6 anion is not reactive towards CH3I in the methylation mechanism. To understand the effect of the solvent on the methylation process, detailed molecular dynamics simulations were performed in DMF using the anions at the C-4", C-6, C-11 and C-12 positions. We find the conformations of the anions not to be affected by the presence of the solvent. The radial distribution functions of the solvent molecules around the O- of the anions demonstrate that DMF molecules cluster around the C-6 anion. The relative strength of the anion-solvent interactions reveal that the solvent molecules provide the largest stabilization to the C-6 anion and prevent the methylation at this position. The latter descriptor was found to be an important factor in explaining the experimentally observed selectivity towards the methylation of the C-4", C-6, C-11 and C-12 anions.

Azithromycin↗

PubMed2004

Azithromycin and dentistry - a useful agent?

OBJECTIVES: Azithromycin has recently replaced clindamycin oral suspension for prop hylaxis of infective endocarditis (IE) in children. It is also currently recommended by the American Heart Association as an alternative to penicillin, along with clindamycin for prophylaxis of infective endocarditis in adults. The objectives of this paper were to firstly, review the current literature on the efficacy of azithromycin as a suitable prophylactic agent in the prevention of infective endocarditis; and secondly, to review its pharmacological properties as a suitable therapeutic agent in the management of odontogenic infections. DESIGN: A review of the literature. CONCLUSIONS: The available evidence from animal models on infective endocarditis supports the efficacy of this drug as a prophylactic agent against oral streptococci. The pharmacological properties of this agent would make it a very promising therapeutic adjunct in the management of odontogenic infections. At present there are only a small number of studies available with valuable data on the efficacy of this relatively new drug. Further investigations comparing this compound with other commonly used adjuncts would be of great benefit.

Adolescent↗

PubMed1996

Helicobacter pylori eradication using one-week low-dose lansoprazole plus amoxycillin and either clarithromycin or azithromycin.

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.

2-Pyridinylmethylsulfinylbenzimidazoles↗

PubMed1993

In vitro activity of azithromycin against Chlamydia trachomatis, Ureaplasma urealyticum and Mycoplasma hominis in comparison with erythromycin, roxithromycin and minocycline.

The in vitro activity of azithromycin against 40 strains of Chlamydia trachomatis, Ureaplasma urealyticum and Mycoplasma hominis was investigated in comparison with erythromycin, roxithromycin and minocycline. All C. trachomatis strains were inhibited by azithromycin at a concentration < or = 0.5 microgram/ml. The initial minimum inhibitory concentration (MIC) of the drug for U. urealyticum was 4 microgram/ml, whereas some resistance against the drug was shown by M. hominis. Erythromycin and roxithromycin presented almost comparable activities, whereas minocycline was slightly more active than macrolides against C. trachomatis (MIC < or = 0.25) and more active against M. hominis (initial MIC < or = 1 micrograms/ml). Only 97% of U. urealyticum strains were susceptible to 8 micrograms/ml of minocycline.

Azithromycin↗

PubMed1994

Chlamydia trachomatis genitourinary infections: laboratory diagnosis and therapeutic aspects. Evaluation of in vitro and in vivo effectiveness of azithromycin.

Chlamydia trachomatis (C.t.) cell culture represents a sensitive method for the diagnosis of chlamydial infection and the only one which makes it possible to determine the susceptibility of an isolate to antibiotics so that an appropriate drug can be selected for individual treatment. In 11 patients, affected by urethroprostatitis and suspected of treatment failure with standard drug regimens, either due to lack of compliance with therapy or antibiotic resistance, C.t. was isolated in McCoy cell culture from urethral swabs, after prostatic massage. The in vitro activity of azithromycin against these isolates and the in vivo efficacy of the drug in the patients treated with a single 1 g dose have been evaluated. All the C.t. strains tested were susceptible to the action of azithromycin (MIC range 0.125-1.0 microgram/ml). Bactericidal values were one dilution higher (MBC range 0.25-2.0 microgram/ml). These in vitro results are consistent with clinical observations as all the patients treated had negative culture at a 4-week follow-up visit.

Azithromycin↗

PubMed2002

Effects of erythromycin, clarithromycin, roxithromycin and azithromycin on murine gut colonization by Candida albicans.

Male Crl:CD1(ICR) BR mice were fed either chow containing Candida albicans or regular chow. The gastrointestinal tract of the C. albicans-fed mice was permanently colonized by the yeast. Groups of C. albicans-colonized mice were subsequently treated either with a macrolide (erythromycin, clarithromycin, roxithromycin or azithromycin) for 10 days or a normal saline solution (controls). Other controls included non-colonized mice receiving the same antibiotics or a saline solution. Our data are as follows: (i) C. albicans-colonized mice treated with each macrolide had highly significant increase in colony counts of C. albicans in their stools compared to C. albicans-colonized mice treated with saline only; (ii) discontinuation of macrolide treatment showed a trend towards lower colony counts, which was not statistically significant (colony counts were sustained even after discontinuation of antibiotic treatment); (iii) dissemination of C. albicans did not occur; (iv) mice fed regular chow treated with the study drugs or saline did not have any yeasts in their stools. In conclusion, oral erythromycin, clarithromycin, roxithromycin and azithromycin cause a modest increase of the C. albicans concentration of the gastrointestinal tract. This increase is not associated with a higher risk of disseminated candidiasis.

Animals↗