Behind the FDA's strictest advisory

Two GROUPS of drugs were under the Food and Drug Administration spotlight last month. Both have been associated with rare but serious side effects, and both were candidates for a "black box" warning, the strongest the FDA issues short of taking a drug off the market. Although one was hit with this safety advisory, the other may have escaped. We look at these drugs and their different fates.

Fluoroquinolones

This class of powerful antibiotics had a black box warning added to its resume. The best-known is probably Cipro, produced by Bayer, which won fame in 2001 as an anthrax treatment, although it's mostly used for urinary tract infections. Another in wider use is Levaquin by Ortho-McNeil, used for respiratory infections.

The risks: Fluoroquinolones are associated with tendon problems, including tendinitis and, more seriously, ruptured tendons (usually the Achilles) that may require surgery and extensive rehab.

The connection is "not exactly intuitive," says Dr. Sidney Wolfe, director of health research at the consumer advocacy group Public Citizen, which campaigns actively on drug safety issues. Although no one can explain why the connection exists, evidence for it has been adding up for years, with problems often reported by patients who are over 60 or have had kidney, heart or lung transplants. This is a different group from those most apt to experience tendon troubles -- namely, thirtysomething jocks.

In the years that these drugs have been marketed, 407 ruptures were reported as of the end of 2007, as were 341 cases of tendinitis, according to Public Citizen. Adverse drug reactions are generally reported about 10% of the time, and in a case like this, where the drug is not a natural suspect, reporting may be even lower.

What happened: Public Citizen petitioned the FDA two years ago to require black box warnings on the professional labels for fluoroquinolones. The group also asked the agency to require medication guides highlighting the warning for consumers as well as "Dear Doctor" letters, alerts sent from drugmakers to doctors, advising them of the new warning. Since the FDA had not acted by January, the organization sued the agency.