Recently published results of a large, carefully conducted retrospective study indicated that use of the antibiotic azithromycin (Zithromax, and others) may increase the risk of cardiovascular death, especially in patients with a high baseline risk of cardiovascular disease.1 One possible mechanism is prolongation of the QT interval, which is known to occur rarely with azithromycin and more frequently with the other macrolide antibiotics erythromycin (Erythrocin, and others) and clarithromycin (Biaxin, and others).

Among the patients who received 347,795 prescriptions for azithromycin, there were 29 cardiovascular deaths, a significantly higher rate than the 42 that occurred among the patients who received 1,348,672 prescriptions for amoxicillin (which does not prolong the QT interval) or the 41 that occurred among the 1,391,180 patients who took no antibiotics. Among patients with the highest baseline risk of cardiovascular disease, treatment with azithromycin, compared to amoxicillin, would have resulted in 245 additional cardiovascular deaths per million courses of the antibiotic.

As with any retrospective study, there could have been some undetected differences between the patients who received one drug or the other, but use of an appropriate non-macrolide alternative2 instead of azithromycin might be reasonable in patients with cardiovascular disease or in those who are taking other drugs that can prolong the QT interval (www.azcert.org).

1. WA Ray et al. Azithromycin and the risk of cardiovascular death. N Engl J Med 2012; 366:1881.

2. Drugs for bacterial infections. Treat Guidel Med Lett 2010; 8:43.

Download complete U.S. English article

The pathogenesis of acne is multifactorial: follicular hyperkeratinization, bacteria, sebum production, androgens and inflammation all play a role. The gram-positive microaerophilic bacteria Propionibacterium acnes promote development of acne lesions by secreting chemotactic factors that attract leukocytes to the follicle, causing inflammation.

A recent letter to the editor of the Annals of Internal Medicine documented a single case of myopathy apparently due to an interaction between simvastatin (Zocor, and others) and green tea. Since it became available generically, simvastatin has surpassed atorvastatin (Lipitor) as the best selling statin. As such, it is probably the most common cause of statin-induced myopathy, which is often a result of drug interactions.

Changes caused by one drug in the absorption, distribution, metabolism or excretion of another may lead to a pharmacokinetic adverse drug interaction (DN Juurlink et al, JAMA 2003; 289:1652). Additive drug interactions, such as vasodilation caused by both sildenafil (Viagra) and nitrates, can also have adverse effects.

Lyme disease, a multisystem bacterial transmitted by Ixodid ticks, particularly in early summer, continues to be a common problem in the USA and many other countries. Since last year (Medical Letter, 30:65, 1988), some new information has become available, but data on the choice, dosage and duration of antibiotic therapy are still available, but data on the choice, dosage and duration of antibiotic therapy are still limited.

A penicillin is the drug of choice for treatment of many infections, but allergic reactions to these drugs occur frequently and, rarely, can be fatal. From 5% to 20% of patients have a history of a rash or some other reaction while taking a penicillin, but maculopapular rashes with ampicillin or amoxicillin, especially in children with infectious mononucleosis, are probably not allergic.

Lyme Disease, a multisystem inflammatory disorder transmitted by lxodid ticks and caused by the spirochete Borrelia burgdorferi, is now the most common tick-transmitted illness in the USA. It has been reported in 32 states and on all other continents except Antarctica. Infected ticks have been found not only in wooded areas, but also on well-maintained suburban lawns (RC Falco and D Fish, Am J Epidemiol, 127:826, April 1988). Optimal treatment for this newly discovered disease is still being determined, but some recommendations based on published experience and work in progress can be made.

Mupirocin (Bactroban - Beecham), a topical antibiotic formerly called pseudomonic acid, was recently approved by the US Food and Drug Administration for treatment of impetigo. It will be sold as a 2% ointment available only by prescription.