Azithromycin ( Zithromax ) and erythromycin resistant Neisseria gonorrhoeae following treatment with azithromycin ( Zithromax ).

A pre-treatment and a 3-week post-treatment isolate of Neisseria gonorrhoeae from a 13-year-old boy treated with azithromycin ( Zithromax ) in a single 1 g oral dose were characterized microbiologically. Both isolates were of the same serovar/auxotype (1B6/non-requiring) and had similar antibiograms apart from erythromycin and azithromycin ( Zithromax ): the pre- and post-treatment MICs (minimum inhibitory concentrations) were: 1 mg/L and 32 mg/L to erythromycin and 0.125 mg/L and 3 mg/L to azithromycin ( Zithromax ). The finding that both isolates were 1B6/NR, had similar antibiograms (other than azithromycin ( Zithromax ) and erythromycin), and no other 1B6/NR isolates were resistant to erythromycin supports the view that macrolide resistance developed following treatment. A high overall level of azithromycin ( Zithromax ) susceptibility was confirmed by testing 67 clinical isolates: MIC90 0.5 mg/L (range 0.023-0.75 mg/L). We conclude that the long half-life of azithromycin ( Zithromax ) which is beneficial in treating chlamydial infection may result in increased selective pressure for resistance in gonococci. This report also highlights the importance of antibiotic susceptibility surveillance of gonococci and stresses the need for appropriate treatment of gonococcal infection, particularly when it is prescribed outwith departments of genitourinary medicine.

Pimozide is often coprescribed with serotonin reuptake inhibitor (SSRI) antidepressants to treat depression in patients with Tourette's syndrome. In human liver microsomes (HLMs), the inhibition of the primary route of pimozide metabolism, N-dealkylation to 1,3-dihydro-1-(4-piperidinyl)-2H-benzimidazol-2-one (DHPBI), by four SSRIs (fluoxetine, sertraline, paroxetine, and fluvoxamine) and azithromycin ( Zithromax ) was tested. Inhibition constants (K(i) values) were estimated from Dixon plots (three HLMs for each inhibitor) using the appropriate enzyme inhibition model by nonlinear regression. At 10 microM paroxetine, sertraline, fluoxetine, or fluvoxamine, the formation of DHPBI from pimozide (10 microM) in HLMs was inhibited by an average (three HLMs) of 7%, 7.7%, 8%, and 16%, respectively, whereas this inhibition did not exceed 55% at the maximum concentrations (100 microM) of the SSRIs tested. Azithromycin ( Zithromax ) had negligible effect on pimozide (10 microM) N-dealkylation (19% at 100 microM azithromycin ( Zithromax )). These inhibition data were compared with ketoconazole, which was included as a positive control of CYP3A inhibition. At 0.1 microM and 0.5 microM ketoconazole, the formation of DHPBI from 10 microM pimozide was inhibited by 32% and 62%, respectively. The K(i) values (+/- SD) of ketoconazole, sertraline, fluvoxamine, azithromycin ( Zithromax ), fluoxetine, and paroxetine were 0.07 microM, 89 +/- 44 microM, 89 +/- 24 microM, 103 +/- 52 microM, 117 +/- 27 microM, and 129 +/- 33 microM, respectively. These values are least 100-fold higher than the expected plasma concentrations after the usual daily doses of the SSRIs and azithromycin ( Zithromax ), suggesting that coadministration of SSRIs and azithromycin ( Zithromax ) are unlikely to markedly diminish the elimination of pimozide in patients. However, in vivo predictions from in vitro data are not always perfect. In vivo, the SSRIs or azithromycin ( Zithromax ) may concentrate in the liver relative to plasma. In addition, the possibility that these drugs could alter pimozide disposition through effects on transport proteins or via promoter repression cannot be ruled out.

Azithromycin ( Zithromax ) for ocular toxoplasmosis.

AIMS: To investigate the efficacy of azithromycin ( Zithromax ) in patients with ocular toxoplasmosis. METHODS: 11 immunocompetent patients with ocular toxoplasmosis were treated with azithromycin ( Zithromax ) (500 mg the first day, followed by 250 mg/day for 5 weeks). Ocular and systemic examinations were performed during active retinitis episodes and all patients were followed for at least 1 year. RESULTS: The intraocular inflammation disappeared within 4 weeks in seven patients, including two cases with progressive retinitis despite previous treatment with pyrimethamine, sulphadiazine, and folinic acid. Recurrence of retinitis occurred in three patients (27%) within the first year of follow up. No systemic side effects of azithromycin ( Zithromax ) were encountered. CONCLUSION: These results indicate that although azithromycin ( Zithromax ) cannot prevent recurrent disease it may be an effective alternative for patients with ocular toxoplasmosis who cannot tolerate standard therapies.

The activity of azithromycin ( Zithromax ) on the infectivity of Chlamydia trachomatis in human amniotic cells.

The effects of azithromycin ( Zithromax ) on the infectivity and growth of Chlamydia trachomatis were investigated in primary human amniotic epithelial cells. Infection was prevented when cultures were exposed to the drug 6 h after inoculation and growth was completely inhibited when the drug was added to cultures 24, 48, 72 h or 7 days after infection. The same inhibition was observed at 0.5, 1.0 and 5.0 mg/L. Ultrastructural observations depicted interruption in the growth cycle of the chlamydia and ghost-like envelopes were present in the near empty inclusions. Azithromycin ( Zithromax ) is effective in inhibiting chlamydial growth no matter when treatment is initiated after infection.