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Doxycycline Now 'the Drug of Choice' Against Anthrax

Posted on: Thursday, 1 September 2005, 15:00 CDT

The antibiotic arsenal against anthrax infection has grown.

After a month of a national preoccupation with the antibiotic ciprofloxacin, also known as Cipro, as the first line of defense, the federal Centers for Disease Control and Prevention have declared the more common doxycycline as "the drug of choice'' for protection against infection after probable exposure to the bacteria.

Health officials had initially called for Cipro to be the first medical punch thrown at any anthrax exposure or infection, causing a run even before the first reports of anthrax by mail surfaced.

Cipro was considered the best protection because it is the newest drug, although it's been around for more than a decade, and thus the one that anthrax germs are least likely to have developed, or been genetically engineered, to have resistance against.

It took several weeks for scientists to identify the strain of anthrax used in the mail attacks and test its susceptibility to Cipro, doxycycline and other antibiotics.

"What we have done is figured out that the isolates so far have entirely been sensitive to doxycycline, so that, essentially, ciprofloxacin and doxycycline are interchangeable,'' said Dr. Pat Meehan, a senior scientist at the Centers for Disease Control and Prevention.

Public health officials who gave out limited supplies of Cipro to postal workers and others suspected of having been exposed are now shifting them to doxycycline. It has these advantages over Cipro: it is in greater supply, costs less, destroys a smaller spectrum of bacteria and has fewer side effects.

Federal guidelines for treating either the inhalation or skin form of the disease also recommend either antibiotic, plus one or two secondary antibiotics.

"I'm really hoping that with these new recommendations, all the people that went out and got stockpiles of Cipro won't be so inclined to take it, and that others won't think they need to do this for protection,'' said Dr. Stuart Levy, director of the center of adaptation genetics and drug resistance at Tufts University Medical School in Boston and a sharp critic of antibiotic misuse.

Levy said it's too early to tell what the long-term effects of such large-scale Cipro use might be, but said he doubted it would make the drug any less useful against anthrax. "The drug's so powerful, it probably won't leave much in the way of resistant bacteria. What I'm worried about is all the other microbes out there that will be exposed to it and become resistant.''

Dr. Lucy Shapiro, a microbiologist at Stanford University, agreed that "this is about the worst thing that can happen in our war on bugs. Our response is going to lead to a big jump in antibiotic resistance. That's the terror.''

Health officials said the new guidelines are intended to bring some balance to the anthrax response.

"It would certainly be healthier, from a broad community sensitivity antibiotic perspective, to have some better balance of folks on different antibiotics,'' said Jeffery Koplan, director of the Centers for Disease Control and Prevention. "Already a number of organisms are resistant to Cipro in part.''

"We won't know for some time what the impact of this will be on antibiotic resistance,'' said Dr. Timothy Flaherty, chairman of the board of the American Medical Association. "But the potential for this accelerating the problem is certainly there. ..."

"We have not put this many people on this number of concentrated antibiotics, if ever, in certainly a long period of time. This amounts to a large clinical trial,'' said Dr. Ivan Walks, chief of the health department in Washington, D.C., where as many as 10,000 people have gone on Cipro and now a doxycycline regimen that may last as long as 60 days.

"We have a lot more experience with people taking doxycycline, and the side effects (mainly a furry or discolored tongue, nausea and sun sensitivity) are more manageable,'' Walks said. "It's more likely that people will stay on it.''

On the Net: http://www.bt.cdc.gov

(Lee Bowman covers health and science for Scripps Howard News Service. E-mail at bowmanl(at)shns.com)

© 2005 Scripps Howard News Service.

All Rights Reserved.

Source: Scripps Howard

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