Wednesday, 21 September 2005 00:00

Oral Antibiotic As Good As Penicillin Shot For Syphilis

WEDNESDAY, Sept. 21 (HealthDay News) -- Just one dose in pill form of the antibiotic azithromycin, better known as Zithromax, treats early-stage syphilis as well as a shot of penicillin.

"Single-dose oral azithromycin is effective in treating syphilis, and may be particularly useful in developing countries in which the use of penicillin G benzathine injections is problematic," wrote the authors of a recent study comparing the two drugs.

"However, recent reports of azithromycin-resistant Treponema pallidum in the United State indicate the importance of continued monitoring for resistance," they added.

Results of the study appear in the Sept. 22 issue of the New England Journal of Medicine.

The U.S. Centers for Disease Control and Prevention report that as many as 32,000 Americans are infected with syphilis each year. The disease, which is caused by the bacterium T. pallidum, can only be spread through direct person-to-person contact, such as sexual intercourse or oral sex. It cannot be contracted through toilet seats, swimming pools or hot tubs, according to CDC.

The first symptom of infection is generally a single sore, called a chancre. Eventually, the chancre disappears, and the infection enters the secondary and then late phase. In the early phase, a single injection of penicillin can easily eradicate the infection. If the disease has progressed to the secondary or late stage, a longer course of antibiotics is usually needed.

The current study included 328 people from Mbeya, Tanzania, who were diagnosed with early syphilis. The average age of the study participant was 27, and almost 72 percent were female.

The study volunteers were randomly assigned to receive either 2 grams of oral azithromycin (163 people) or 2.4 million units of penicillin G benzathine by injection (165 people).

Nine months after treatment, almost 98 percent of those in the azithromycin group were cured vs. 95 percent in the penicillin group.

"This is a well-carried out study that adds options for treatment, but not options we hadn't already thought of," said Dr. Charles Gonzalez, an infectious disease specialist at New York University Medical Center.

"We already use Zithromax for penicillin-allergic patients. There are also logistical benefits to a pill. It's actually a little bit less expensive, because you don't have to have a pharmacist mix it, and a nurse to administer it. It's also easier to keep a pill stored on a shelf," he said.

But, he added, "The difficulty is, with large-scale distribution, we worry about a resistance pattern."

"The presence of resistance in North America and Ireland makes the routine use of azithromycin a very risky proposition," said Sheila Lukehart, a professor of medicine at the University of Washington in Seattle.

Last year, Lukehart published a study in the New England Journal of Medicine that found almost 90 percent of samples taken in Dublin, Ireland, and nearly 40 percent of samples of T. pallidum taken in San Francisco contained a genetic mutation making it resistant to azithromycin.

"The decision about using azithromycin needs to be based carefully on what you know about the strains in that community, which means we need to be doing surveillance. So far, there's no concerted surveillance effort ongoing in most of this country and worldwide," she explained.

"There are macrolide-resistant T. pallidum spreading along the West Coast right now. We don't know whether this was a single resistant strain that is now spreading, or if it's new resistance that is developing. We don't know which of those two is occurring," she added. "If it's a new resistance that is developing, it could doom azithromycin for treatment of syphilis," Lukehart said. "If it's a limited numb