(1) Research into macrolide immunomodulation for chronic pulmonary disorders demonstrates consistent positive effects, although of types other than seen with diffuse panbronchiolitis. These effects, together with their inhibitory activity on biofilms, have the potential to make them a useful option. (2) The benefits for CAP are consistent, and higher when a macrolide is given with another atypical agent than if the other atypical agent is given alone, suggesting a non-antibacterial benefit. (3) Recent research of the immunomodulatory properties of azithromycin imply that azithromycin may have a previously unknown short-term biphasic effect on inflammation modulation: enhancement of host defence mechanisms shortly after initial administration followed by curtailment of local infection/inflammation in the following period. (4) Additional in vivo research is needed prior to developing any firm conclusions.

There is no doubt that owing to the prolific use of the macrolides and azithromycin over the past several years, resistance has developed and is increasing in incidence. I believe we should re-evaluate the use of these antibiotics for our patients and consider parameters other than the negative in-vitro results. Firstly, microbiology laboratories should return to the habit of providing the clinician with MIC values for pathogenic isolates rather than generic susceptibility reports ((S)usceptible, (I)ntermediate, (R)esistant) that are based on standard disc diffusion testing. Although agar dilution MIC testing is a bulky and labour intensive practice, it provides the best data when conducted in the appropriate environment. Secondly, and more importantly, these MIC values need to be compared with in-vivo antibiotic pharmacokinetics and pharmacodynamics. Although it is possible to compare MIC values directly with serum concentrations of beta-lactams and aminoglycosides, this is not a valid practice for azithromycin or the macrolides. MICs of azithromycin and the macrolides must be compared with the infection site and phagocytic cell concentrations to determine the utility, or lack thereof, of one of these agents. Whereas azithromycin cellular penetration allows maximal pharmacodynamics potentially even against moderately or highly resistant pneumococci, the macrolides do so less optimally. Although there are no reports of widespread clinical failures resulting from macrolide/azalide resistance in pneumococci, it is expected that such reports will appear once the isolates become consistently highly resistant. This is likely to affect the macrolides, erythromycin and clarithromycin, before the azalide, azithromycin owing to the differences in pharmacokinetics of these drugs. Until then, it will be important to determine the MICs of not just one macrolide, but of all macrolides and azalides for the isolates. This will allow the clinician to make a pharmacokinetically and pharmacodynamically sound choice. By choosing clinical MIC breakpoints of 4-8 mg/L for oral macrolides and < or = 32 mg/L for oral azithromycin, rather than the present standard breakpoints, the clinician can make a macrolide/azalide choice that will optimize the pharmacodynamics of the drug against the isolated pathogen and result in the best possible clinical outcome. Once data concerning the cellular penetration of intravenous formulations of these drugs becomes available, it will be possible to develop clinical breakpoints for these formulations as well. Only through utilizing good antibiotic prescribing practices and by using the drugs appropriately when they are used, can resistance trends be stemmed. In this way, not only does a clinician treat the patient more effectively, but they also extend the antibiotic's useful life.

The addition of twice-weekly azithromycin significantly decreased the incidence of exacerbation and 24-hour sputum volume and may have stabilized the PFTs and PFs in this 11-patient pilot study. The results of this study justify further investigation of adding azithromycin to the treatment regimens of patients with bronchiectasis for its disease-modifying effects.

No abstract

Azithromycin is a critical component of an integrated disease elimination program against trachoma. This study was conducted to evaluate whether azithromycin has a pharmacokinetic interaction with the combination of ivermectin and albendazole. Eighteen healthy volunteers were administered single doses of azithromycin, ivermectin/albendazole, and the combination of the three agents in random, crossover fashion. To assess the presence of interactions, test (combination) and reference (single dose) data were compared using an estimation approach. Compared with reference phases, the geometric mean values for the combination arm's azithromycin AUC(0-t) and C(max) were increased approximately 13% and 20%, respectively, albendazole AUC(0-t) decreased by approximately 3% and C(max) increased approximately 3%, and ivermectin AUC(0-t) and C(max) were increased 31% and 27%, respectively. Albendazole sulfoxide AUC(0-t) and C(max) were decreased approximately 16% and 14%, respectively. All treatments were well tolerated. The interactions for azithromycin and albendazole were minimal although the increase in ivermectin exposure requires further study.