CHICAGO — A single 2-g dose of azithromycin cures early syphilis as effectively as injected penicillin G benzathine, Dr. Edward W. Hook III said at a conference on sexually transmitted disease prevention sponsored by the Centers for Disease Control and Prevention.
However, Dr. Hook cautioned that the federally sponsored randomized controlled trial did not include any HIV-positive patients, so its results can't support the use of azithromycin in this population.
“This is the very group in which macrolide-resistant Treponema pallidum mutations have emerged in association with azithromycin treatment,” said Dr. Hook of the University of Alabama, Birmingham. “I would certainly not recommend treating these patients with azithromycin for early syphilis.”
Neither should the drug be used for syphilis in pregnant women. “In light of the history of macrolide treatment failures among pregnant women, I would caution very, very strongly against treating them with azithromycin for syphilis,” Dr. Hook said.
The trial compared the efficacy and safety of 2 g of azithromycin given orally with those of 2.4 million U of penicillin G benzathine in 517 patients with early syphilis. Most of the patients (80%) were in Madagascar; the rest were seen at U.S. clinics.
The patients' mean age was 24 years; 26% had primary syphilis, 46% had secondary syphilis, and 28% had presumed early latent syphilis (a sexual partner in the past 12 months with confirmed syphilis).
Serologic cure rates at 3 months were similar in both groups in the intent-to-treat analysis (74% azithromycin vs. 76% penicillin). At 6 months, the cure rates were still not significantly different (77% azithromycin vs. 78% penicillin). Results at 3 and 6 months in the per-protocol analysis were almost identical, Dr. Hook said.
U.S. patients exhibited slightly, but not significantly, higher cure rates than did patients in Madagascar.
Serious adverse events were slightly more common in the penicillin group than they were in the azithromycin group (10 vs. 8, respectively). However, none of these was considered related to the study medication. Nonserious adverse events, especially gastrointestinal distress, were significantly more common among the patients taking azithromycin (61% vs. 46% for penicillin).
The most common adverse events were gastrointestinal, with 24% of the azithromycin group experiencing some upset, compared with 7% of the penicillin group. However, only three patients taking azithromycin vomited.
Cutaneous reactions were more common among those taking penicillin (4% vs. 1%), as were administration-related adverse events (10% vs. 5%).