US consumer group, Public Citizen, is on the warpath again and in its line of sight this time are the fluoroquinolone antibiotics Levaquin and Cipro, which it says have been linked to ruptured tendons.

Public Citizen has petitioned the US Food and Drug Administration along with the attorney general for the State of Illinois, Lisa Madigan, saying there were around 260 cases each of tendon ruptures, tendonitis and other tendon disorders in an eight-year period to the end of 2005. The large majority, 61%, were linked to the use of Johnson & Johnson's Levaquin (levafloxacin) while a large proportion of the remainder - 23% - were associated with Bayer's Cipro (ciprofloxacin)'s use (although the latter is also available generically).

“The numbers are startling. Tendon ruptures associated with these drugs continue to occur at a disturbing rate but could be prevented if doctors and patients were more aware of early warning signals, such as the onset of tendon pain, and switched to other antibiotics,” argued Sidney Wolfe, director of Public Citizen's Health Research Group. It believes that the fluoroquinolone group of drugs are toxic to tendon fibres and may cut the supply of blood causing the tendon to rupture. Most commonly, the Achilles' tendon has ruptured in patients taking the antibiotics, leading to severe pain and difficulty walking, but other sites reported include the biceps, the hand and the thumb.

Although the labelling already does warn of tendon ruptures following a 1996 Public Citizen petition, it is “buried in the list of possible adverse reactions,” said the consumer group, “and so has been inadequate.” The Illinois attorney general followed this up in 2005 with a call for a black box warning - the strongest available - but said the FDA “has never responded substantively.”

If more doctors and patients were aware of the early warning signals - such as the onset of tendon pain - they could be switched to other antibiotics, the group says. “The numbers are startling. Tendon ruptures associated with these drugs continue to occur at a disturbing rate, but could be prevented. The FDA must act and require black box warnings and patient information guides,” Public Citizen finishes. Some 45% of all prescriptions for fluoroquinolone antibiotics over the last four years were written for Levaquin.

Meanwhile, the FDA this week said it has given the first nod of approval to “several” injectable generic versions of Bayer's Cipro. In 2005, according to the online magazine, Drug Topics, Cipro iv injection was on the top 200 list of highest-selling brand-name drugs in the USA, with wholesale acquisition costs used in hospitals totalling $115.3 million. Cipro lost its principal patent protection in the USA in 2004, but Levaquin's is in place until 2010.