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...

The US Food and Drug Administration (FDA) recently approved the marketing of clarithromycin (Biaxin - Abbott), a macrolide antibiotic, and omeprazole (Prilosec - Astra Merck), a proton pump inhibitor, for concurrent use in treatment of duodenal ulcers associated with Helicobacter pylori.

Dirithromycin (Dynabac - manufactured by Lilly, distributed by Bock), an oral macrolide antibiotic chemically similar to erythromycin, clarithromycin (Biaxin) and azithromycin (Zithromax), has been approved for marketing by the US Food and Drug Administration (FDA).

The FDA has required the manufacturer of the secondgeneration antipsychotic quetiapine (Seroquel) to add a warning to the labeling saying that use of the drug should be avoided in combination with other drugs that prolong the electrocardiographic QTc interval (Table 1). The warning is based only on postmarketing reports of QT-interval prolongation in patients who overdosed on the drug, had concomitant illness, or were taking other drugs known to cause electrolyte imbalances or increase the QT interval. QT prolongation can lead to torsades de pointes, a potentially fatal cardiac...

Telithromycin (Ketek - Aventis) has been approved by the FDA for oral treatment of mild to moderate community-acquired pneumonia, acute exacerbations of chronic bronchitis and acute bacterial sinusitis in patients age 18 and older. The drug is the first in a new class of antibiotics, the ketolides, derived from the macrolide erythromycin. Telithromycin has been marketed in Europe since 2001.

Clarithromycin (Biaxin - Abbott) and azithromycin (Zithromax - Pfizer), two macrolide antibiotics chemically related to erythromycin, have been approved by the US Food and Drug Administration for treatment of respiratory, skin, and skin structure infections. Azithromycin has also been approved for treatment of nongonococcal urethritis and cervicitis caused by Chlamydia trachomatis.

Serious adverse interactions between drugs continue to be reported. Many of these are due to inhibition or induction of cytochrome P450 (CYP) enzymes, particularly CYP3A4. CYP3A is thought to be involved in the metabolism of more than 50 percent of currently prescribed drugs.2 CYP3A4, which is more abundantly expressed than CYP3A5, accounts for most CYP3A activity in vivo.

Cefdinir (Omnicef - Parke-Davis), a third-generation oral cephalosporin, has been approved by the FDA for treatment of acute sinusitis, otitis media, acute exacerbations of chronic bronchitis, pharyngitis, community-acquired pneumonia and skin infections. Other drugs available for these indications are reviewed in The Medical Letter Handbook of Antimicrobial Therapy, 1998.

The FDA has warned that use of the macrolide antibiotic clarithromycin (Biaxin, and generics) may increase the risk of cardiovascular morbidity and mortality in patients with heart disease.

Fexofenadine (fex oh fen' a deen) hydrochloride (Allegra - Hoechst Marion Roussel) has been approved by the US Food and Drug Administration for treatment of seasonal allergic rhinitis. An active metabolite of terfenadine, fexofenadine is being heavily advertised as "nonsedating...without 'black box' warnings."