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WARNING— Increased Risk Of Tendinitis And Tendon Rupture With All Fluoroquinolone Antibiotics Public Citizen’s Health Research Group successfully petitioned the Food and Drug Administration (FDA) to add a warning for doctors to the labeling, or package, for all fluoroquinolone antibiotics about the risk of tendinitis, including the possibility of complete tendon rupture. The fluoroquinolone antibiotics includes drugs such as ciprofloxacin (CIPRO). This adverse reaction most... |
WARNING— Increased Risk Of Tendinitis And Tendon Rupture With All Fluoroquinolone Antibiotics Public Citizen’s Health Research Group successfully petitioned the Food and Drug Administration (FDA) to add a warning for doctors to the labeling, or package, for all fluoroquinolone antibiotics about the risk of tendinitis, including the possibility of complete tendon rupture. The fluoroquinolone antibiotics includes drugs such as ciprofloxacin (CIPRO). This adverse reaction most frequently involves the Achilles tendon, the tendon that runs from the back of the heel to the calf. Rupture of the Achilles tendon may require surgical repair. Tendons in the rotator cuff (the shoulder), the hand, the biceps, and the thumb have also been involved. This reaction appears to be more common in those taking steroid drugs, in older patients, and in kidney transplant recipients but cases have occurred in people without any of these risk factors. The onset of symptoms is sudden and has occurred as soon as 24 hours after starting treatment with a fluoroquinolone. Most people have recovered completely after one to two months. If you experience unexpected tendon pain while taking a fluoroquinolone antibiotic stop the drug immediately, call your doctor, and rest. |
The July 2004 issue of the Canadian Adverse Drug Reaction Newsletter highlighted drug interactions between of a number of the fluoroquinolone antibiotics and the anticoagulant (blood thinner) warfarin (COUMADIN). The combination of these drugs can enhance the effect of warfarin that can result in an increased risk of bleeding.
The fluoroquinolone antibiotics marketed in the U.S. are listed in the table below. These antibiotics are primarily used to treat respiratory and urinary tract infections; prostate infection; blood infection; and skin, soft-tissue, bone and joint infections. The fluoroquinolones as a family of antibiotics are often prescribed when they are not needed (see Worst Pills, Best Pills News June 2004 and June 2003).
Fluoroquinolone Antibiotics Available In The U.S. Ciprofloxacin (CIPRO) |
Through January 15, 2004, Health Canada, the Canadian equivalent of the Food and Drug Administration (FDA), received 57 reports of suspected interactions associated with fluoroquinolones and warfarin. The table below lists the fluoroquinolone antibiotic, its U.S. brand name, and the number of cases associated with each drug:
Canadian Drug Interaction Reports Of Interactions Between Fluoroquinolones And Warfarin
Fluoroquinolone Antibiotic CASES
Ciprofloxacin (CIPRO) 10
Gatifloxacin (TEQUIN) 13
Levofloxacin (LEVAQUIN) 16
Moxifloxacin (AVELOX) 12
Norfloxacin (NOROXIN) 6
Ofloxacin (FLOXIN) (marketed in Canada in December 1990) 0
These 57 reports involved 46 patients, 60 years of age and older. Forty-nine reports were considered serious, with 16 involving adverse effects resulting in hospitalization. Four patients between the ages of 70 and 90 died. One of these patients was taking ciprofloxacin, two were on gatifloxacin, and one on levofloxacin. A direct cause-and-effect relationship is difficult to assess because of the complexity of the medical conditions of the patients.
A previous study, based on data from the FDA, found 64 reports of bleeding events had been reported in people using warfarin and ciprofloxacin.
The standard blood test used to assess anticoagulation, or blood thinning, in patients taking warfarin is called the international normalized ratio (INR). The lower the number the less the likelihood of abnormal bleeding. A therapeutic INR is between 2.0 and 3.0. In this group of 46 patients, the INRs reported were as high as 50. In 15 of the reports, the INR had been stabilized with warfarin treatment before the fluoroquinolone antibiotic treatment was started.
The interaction warning between fluoroquinolone antibiotics and warfarin is in the official Canadian product monographs, the equivalent of the FDA- approved professional product labeling (or package insert) for these drugs. These government-approved documents are written for physicians and pharmacists and, in general, are not routinely distributed to patients at the time a prescription is filled in either country.
The U.S. professional product labels for the fluoroquinolones warns that an interaction does exist with warfarin for ciprofloxacin, levofloxacin, norfloxacin, and ofloxacin. The professional information for gatifloxacin and trovafloxacin indicates that no interaction exists between these drugs and warfarin. For the rest of the fluoroquinolones available in the U.S., enoxacin, gemfloxacin, lomefloxacin, and moxifloxacin, the professional labels say that there is no interaction with warfarin but that the status of blood clotting (bleeding potential) should be monitored with a blood test.
What You Can Do
You should consider that all fluoroquinolone antibiotics have the potential to interact with warfarin and your physician should be ordering blood tests to monitor the status of your blood clotting if one of these antibiotics is needed and you are using warfarin. This is the safest thing to do.
