Too much of a good thing?

Experts worry about antibiotic resistance as Cipro use increases

From Elizabeth Cohen
CNN Medical Unit

(CNN) -- The anthrax scare has forced thousands of Americans to begin taking the powerful antibiotic ciprofloxacin to combat the bacteria because they may have been exposed to it.

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While taking the drugs may give some patients peace of mind, it is causing concern among public health officials.

They worry that increased use of Cipro could exacerbate an already serious problem of antibiotic resistance.

"It's very alarming," said Dr. Barry Kreiswirth of the Public Health Research Institute, "because I don't think we know how many people are actually taking it at the moment.

"We also don't really know what is going to be the downstream effect of so many people taking an antibiotic for such a long period of time."

But it is not the anthrax they are worried about. Experts say the anthrax seen so far will not become resistant to antibiotics because it is not contagious from person to person.

Cipro is in a class of antibiotics often used to kill bacteria that do not respond to other drugs. Experts worry that the more Cipro gets used, the greater the chance that harmful bacteria other than anthrax will learn how to outsmart it.

If that happens, Cipro and the other antibiotics in its class could be rendered useless.

"For cancer patients, for transplant patients, for very, very sick patients, ciprofloxacin and members of that same family are critically, critically needed," said Dr. Stuart Levy, director of the Center for Adaptation Genetics and Drug Resistance at Tufts University medical school in Boston, Massachusetts.

"They are often the drug of last resort. We don't want to lose them."

How do bacteria become resistant to antibiotics? Prolonged exposure is the culprit.

When a person is taking an antibiotic -- Cipro for instance -- it works because the bacteria do not have any defenses against the drug.

Over time, though, the bacteria develop ways to fight off the medicine -- they become resistant to it.

The person taking Cipro can sneeze and pass the resistant bacteria along to someone else. When that person gets sick, Cipro will not work.

The cycle continues until eventually the problem spreads across the nation.

So as thousands of Americans line up for their doses of Cipro, why aren't public health officials using other drugs?

The Centers for Disease Control and Prevention has determined that doxycycline works just as well against anthrax, and concerns about resistance to the drug aren't as great because it isn't as powerful or useful as Cipro. In fact, the CDC is already giving out doses of doxycycline as well as Cipro.

The problem may be a psychological one. People have been hearing so much about Cipro, they do not want to take anything else.

"Until we educate people that doxycycline is as effective as Cipro, we don't want to create concern in people that they're not getting the best drugs," said Dr. David Fleming, the CDC's deputy director for science and public health.

"So we're doing this education right now to help people understand that these two drugs are equally as effective."