Antibiotics May Prevent Lyme Disease

From the WebMD Archives

June 12, 2001 -- New findings released Tuesday show that an antibiotic taken within 72 hours of being bitten by a deer tick carrying Lyme disease can prevent people from developing the illness.

Only about 3% of people who are bitten by ticks will develop Lyme disease, which is characterized by persistent fatigue and pain. But the new study confirms that the risk is highest for people bitten by ticks that haven't yet reached the adult stage and are at least partially engorged with blood. Although the study will not be published until next month, The New England Journal of Medicine released it early because of the treatment potential.

"The important thing I think is that Lyme disease can be prevented," says the study's author Robert B. Nadelman, MD, of New York Medical College and the Lyme Disease Diagnostic Center at Westchester Medical Center in Valhalla, N.Y.

He tells WebMD that although antibiotics won't be recommended for everyone with tick bites this summer, knowing they work gives doctors and patients a much-needed addition to their prevention methods.

The best-known ways to prevent Lyme disease are avoiding areas known to be infested with deer ticks; wearing clothing that covers your skin when you are potentially going to be exposed to ticks; and checking your body, hair, and clothes carefully for any signs of a tick after being in the woods or other areas where ticks are prevalent.

In Nadelman's study of nearly 500 adults, a single dose -- two pills -- of the antibiotic doxycycline taken within 72 hours of being bitten was 87% effective in preventing Lyme disease.

But because the antibiotic treatment causes side effects like nausea and vomiting in about 30% of people, experts say doctors shouldn't give it unless the person is fairly certain the tick that bit them was fat -- as opposed to flat, meaning it was somewhat engorged -- and that it was indeed a tick.

"Many persons living in areas where there is a lot of Lyme disease are experts at identifying ticks," says Nadelman. "But on the other hand there are many people ... bringing in what they think are ticks but which many times are debris, dirt, spider mites, or perhaps other kinds of ticks that are not deer ticks."


If you've been infected with Lyme disease without realizing it, a characteristic 'bulls-eye' rash will develop at the site of the bite within days to weeks. At that point, a 10- to 21-day course of antibiotics will be started and the success rate of treatment is about 95% or better, according to Eugene D. Shapiro, MD, of Yale University School of Medicine in New Haven, Conn.

"There's a myth that Lyme disease produces these horrible, intractable symptoms," he says. "But the therapy is extremely effective."

He says although it's good to know the antibiotic prevention works for people at highest risk, he worries that anxiety over the threat of Lyme disease will drive some people to want to take preventive antibiotics every time they think they spot something that could be a tick on themselves, their spouse, or their children.

A small percentage of people who do contract Lyme disease will continue to have symptoms such as fatigue, arthritis, muscle and joint pain, and mood and memory problems after undergoing the standard 10- to 21-day course of antibiotics. Some doctors treat this "chronic" Lyme disease with long-term antibiotics, but few studies have shown the treatment to be effective.

Another study in the same issue of the journal confirms that taking antibiotics for longer than the standard 21-day course doesn't significantly improve how people feel or their quality of life.

Study author Mark S. Klempner, MD, reports little difference in physical or mental symptoms among people with chronic Lyme disease symptoms given 90 days of intravenous and oral antibiotic treatment or a placebo. The study included people who still had evidence of the bug that causes Lyme disease in their blood and those who did not.

Klempner, of the New England Medical Center in Boston, says although some patients will continue to have symptoms after their initial treatment with antibiotics, continuing the same treatment for months or years does not appear to be the best way to help these patients.

WebMD Health News Reviewed by Gary D. Vogin, MD
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