Drugs online research references
Jpn J Antibiot. 1999 Jul;52(7):497-503.
[Tissue penetration properties of macrolide antibiotics--comparative tissue distribution of erythromycin-stearate, clarithromycin, roxithromycin and azithromycin in rats]
[Article in Japanese]
Yoshida H, Furuta T.
Pharmaceutical Research Laboratories, Taisho Pharmaceutical Co., LTD.
The ability of antibiotics to penetrate the target organs is an important factor for the clinical effects and side effects in the treatment of infection. In the present study, the comparative tissue distribution of 4 kinds of macrolide antibiotics was determined in rats. After oral administration of 20 mg/kg, roxithromycin (RXM) had the highest plasma concentration, and clarithromycin (CAM) has the second highest. The Cmax of RXM and CAM were 2.7 and 1.0 micrograms/ml, respectively. On the other hand, both levels of erythromycin-stearate (EM-S) and azithromycin (AZM) were extremely low, with a Cmax of 0.1 microgram/ml. Concentration of the 4 compounds were measurable in the liver, kidney, spleen, lung and heart. The concentration in all tissues for each compound were significantly higher than those in the plasma. AZM had the most sustained and the highest tissue levels. The distribution patterns of RXM and AZM were almost similar to the case of EM-S, in that the highest tissue concentration was observed in the liver, followed in descending order by concentration in the kidney, spleen, lung and heart. On the other hand, CAM had the highest concentration in the lung, and was moderated in the liver. Major clinical indications are infections of the respiratory tracts, and commonly reported side-effects are hepatotoxity. Therefore, it is worth noting that the lung levels of CAM were significantly higher than in the liver, as the separation of clinical effects and side-effects.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10516929&dopt=Abstract
word match zithromax online literature
Eur J Clin Microbiol Infect Dis. 1991 Oct;10(10):834-42.
Effects of environmental factors on the in vitro potency of azithromycin.
Retsema JA, Brennan LA, Girard AE.
Central Research Division, Pfizer Inc., Groton, CT 06340.
The effects of media, pH, cations, serum, CO2 or anaerobic atmosphere, inoculum size and time of incubation on the in vitro potency of azithromycin were determined. The potency of azithromycin against all genera was particularly sensitive to changes in pH. The MIC for Staphylococcus aureus strains ranged from 50 micrograms/ml at pH 6 to less than or equal to 0.025 micrograms/ml at pH 8; for erythromycin the MIC change was less (1.6 to 0.05 micrograms/ml). Incubation for 18 h in 5% CO2 or an anaerobic atmosphere (10% CO2, 10% H2, 80% N2) lowered the pH by approximately 0.8 units with gram-negative organisms and 0.4 units with gram-positive organisms. This resulted in an MIC eight times greater than the aerobic MIC. In addition, the MIC100 for azithromycin and erythromycin against Bacteroides strains growing in Wilkins-Chalgren broth fell from 3.1 micrograms/ml in the anaerobic atmosphere to 0.2 and 0.4 micrograms/ml, respectively, when using the Oxyrase enzyme system to remove oxygen. With the Oxyrase system, the pH of the medium at the MIC remained at 7.2, while it fell to 6.7 in the anaerobic gas mixture. An increase in potency for both agents was also observed with other anaerobic species when using the Oxyrase system. The addition of serum produced an increase in potency of azithromycin and erythromycin that correlated with an increase in pH during incubation, despite the use of buffered media. Adding cations to Mueller-Hinton broth resulted in increased MICs for gram-negative organisms; the highest increases observed were four-fold for Escherichia coli.(ABSTRACT TRUNCATED AT 250 WORDS)
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1662627&dopt=Abstract
word match zithromax online literature
Eur J Clin Microbiol Infect Dis. 1991 Oct;10(10):843-6.
Lack of emergence of significant resistance in vitro and in vivo to the new azalide antibiotic azithromycin.
Retsema JA, Girard AE, Brennan LA, Cimochowski CR, Faiella JA.
Central Research Division, Pfizer Inc., Groton, CT 06340.
In vitro experiments were performed in which 6 to 12 strains of Staphylococcus aureus, Streptococcus pyogenes, Haemophilus influenzae and Enterobacteriaceae were passaged nine times in sub-lethal concentrations of azithromycin or control antibiotics. Streptococcus pyogenes and Staphylococcus aureus quickly became resistant to rifampin as the MIC90 increased from 0.1 to greater than 50 micrograms/ml for both species. The MIC90 of azithromycin, erythromycin, amoxicillin and cefaclor increased by three dilutions for Staphylococcus aureus. The MIC values of azithromycin for Streptococcus pyogenes, Haemophilus influenzae and Enterobacteriaceae strains did not change significantly. However, for Haemophilus influenzae and the Enterobacteriaceae strains, the MIC values of erythromycin and oral cephalosporins increased four-fold. In the in vivo experiments, mice infected with Staphylococcus aureus or Escherichia coli contaminated sutures were administered azithromycin for three days, and on day 6 viable bacterial cells were recovered from the infection site. The sustained tissue concentrations of azithromycin indicated that the organisms would have been continuously exposed to azithromycin at the site of infection. Colonies isolated from azithromycin-treated and non-treated mice were cultured and their susceptibility to azithromycin compared. The azithromycin MIC values for Staphylococcus aureus cultures from treated and non-treated animals were identical. The azithromycin MICs for Escherichia coli recovered from treated animals were on average, less than one dilution higher than for control cultures. Emergence of significant resistance to azithromycin in the laboratory was not observed with the pathogens tested.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1662628&dopt=Abstract
word match zithromax online literature
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