Cipro tendon ruptures can involve the Achilles heel, shoulder, hand, bicep or thumb and is especially increased in patients older than 60, or people who have received kidney, heart or lung transplants, as well as people on steroid therapy. This antibiotic is in a class of drugs called fluoroquinolones, a prescription drug used to treat common respiratory infections including bacterial sinusitis, bronchitis, and pneumonia in adults, but it has also been used "off-label".

Bayer AG developed Cipro--the first fluoroquinolone to be on the market—in 1987: since that time studies have shown that Cipro and other fluoroquinolones have been misprescribed and overprescribed and Cipro should only be used as a "last resort" antibiotic.
One study on lab rats found that the rodents' Achilles tendons underwent "degenerative alterations" shortly after Cipro therapy began and ruptures continued to occur even after the animals stopped receiving the drug. Researchers now believe that Cipro may cause a toxic effect on connective tissue structures, thereby explaining tendon ruptures. Researchers speculate that Cipro tendon rupture may be as high as 1 in 250.
On July 8, 2008 the FDA gave Cipro a black box warning after Public Citizen, a public interest watchdog organization, brought the issue to trial in 2006. Black box warnings are the strongest warnings the FDA issues. The warning appears in bold type, surrounded by a black box to make sure it stands out.
The FDA recommends that physicians should advise patients to stop taking Cipro at the first sign of tendon pain, swelling or inflammation, as these symptoms can precede tendon rupture.