WASHINGTON (AP) - The government will soon publish the exact doses of medicines other than Cipro that people exposed to anthrax can take to ward off infection.

The federal government is aiming to inform panicked Americans that other widely available - and cheaper - antibiotics than Cipro can also fight anthrax.

The generic antibiotics doxycycline and penicillin have long been approved by the Food and Drug Administration as treatments for anthrax, while the newer Cipro was approved just last year.

But as worries spread, Cipro is the drug disappearing from pharmacy shelves. Americans are citing concerns there might not be enough treatment, even though numerous manufacturers churn out millions of doxycycline and penicillin tablets each year.

“It seems as if in the minds of some people, that's the only drug,” FDA drug chief Dr. Janet Woodcock said of Cipro Wednesday. “That actually isn't the case.”

So within a week, the FDA will publish specific instruction on what dose of doxycycline and penicillin can be used, and for how long, to ward off infection among people exposed to anthrax spores.

These older antibiotics are “relatively inexpensive and readily available,” Health and Human Services Secretary Tommy Thompson told Congress Wednesday.

The information is important because Cipro, like all medications, can cause some serious side effects. Therefore, health officials stress it should be used only by those who really need it - not worried people who haven't been exposed to anthrax.

All antibiotics can cause allergic reactions. Cipro can cause central nervous system side effects such as dizziness, confusion and depression, as well as ruptures of tendons. Doxycycline's main warnings mention permanently staining children's teeth and making the skin sensitive to sunlight.

“Doxycycline is better tolerated,” said Dr. Jeffrey Koplan, director of the Centers for Disease Control and Prevention.

Indeed, people who were exposed to anthrax but show no symptoms after a few days should expect their doctors to switch them from Cipro to doxycycline, Koplan said.

Days after anthrax was first discovered in a Florida tabloid office, the CDC privately sent state health departments dosage instructions for Cipro, doxycycline and a penicillin relative called amoxicillin for anyone exposed to anthrax.

For adults, the CDC-recommended doses are 500 milligrams of Cipro twice a day for 60 days; or 100 mg of doxycycline twice a day for 60 days; or 500 mg of amoxicillin three times a day for 60 days.

The CDC recommendations warned that pregnant women were recommended to take only amoxicillin, not the other drugs; doxycycline was the first choice for the elderly; and children need special doses based on their weight.

The FDA didn't object to the CDC's recommendations but will also publish a penicillin dose.

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