T he fluoroquinolone antibiotics are an important, fre- quently prescribed group of medications. Fluoro- quinolone adverse events involving the central nervous system (e.g., dizziness, headache, seizures, psychosis) are well known. 1-11 However, less recognized are fluoro- quinolone-associated peripheral neuropathies, and only a few reports 12-16 and one article 17 have been published in the medical literature regarding such events, which are usually described as mild and of short duration. In contrast, in recent years hundreds of reports involving fluoroquinolone-associated events involving the central nervous system (CNS), musculoskeletal system, and pe- ripheral nervous system (PNS) have been posted on Inter- net Web sites by patients or concerned family members. Many of these events are described as severe and long- lasting, causing substantial pain, impairment of function- ing, and, in some cases, long-term disability. In order to provide a central forum for these people, in February 1999 the Quinolone Antibiotics Adverse Reaction Forum was established at www.geocities.com/quinolones/ to provide a central forum for individuals to self-report adverse events experienced in association with fluoroquinolones. The Web site also offers links to the National Institutes of Health and other relevant medically oriented Web sites, and encourages people to use its link to the Food and Drug Administration’s (FDA’s) MedWatch program for filing official reports. As of October, 2001, the site received more than 73 000 visitors and 5000 posts. With the assistance of members of this Web site, a survey of cases involving PNS The Annals of Pharmacotherapy ■ 2001 December, Volume 35 ■ 1 Peripheral Neuropathy Associated with Fluoroquinolones Jay S Cohen RESEARCH REPORTS www.theannals.com Infectious Diseases Author information provided at the end of the text. OBJECTIVE: To survey cases of fluoroquinolone-associated adverse events that included peripheral nervous system (PNS) symptoms posted on Internet Web sites. METHODS: Cases were obtained with the assistance of members of Web sites formed by people sustaining fluoroquinolone-related events. Information obtained met the standards of MedWatch, and each reported case was assessed using the Naranjo probability scale. RESULTS: In contrast to previous reports suggesting that fluoroquinolone-associated PNS events are mild and short-term, 36 of the 45 cases reported severe events that typically involved multiple organ systems. Although many newer cases are still evolving, symptoms had lasted more than three months in 71% of cases and more than one year in 58%. Onset of adverse events was usually rapid, with 15 (33%) events beginning within 24 hours of initiating treatment, 26 (58%) within 72 hours, and 38 (84%) within one week. Sixty courses of fluoroquinolones were prescribed: levofloxacin (n = 33 cases), ciprofloxacin (n = 11), ofloxacin (n = 6), lomefloxacin (n = 1), trovafloxacin (n = 1); in eight cases the same antibiotic was prescribed twice. CONCLUSIONS: These cases suggest a possible association between fluoroquinolone antibiotics and severe, long-term adverse effects involving the PNS as well as other organ systems. The severity of these cases may reflect a different population than typically reported to drug companies or MedWatch, which often originate from healthcare providers. In contrast, Internet Web sites may provide a forum for patients experiencing adverse effects that have not resolved promptly. Further study is warranted. Meanwhile, the occurrence of PNS symptoms during fluoroquinolone therapy should prompt immediate discontinuation of the agent used. KEY WORDS: adverse events, ciprofloxacin, fluoroquinolones, levofloxacin, lomefloxacin, ofloxacin, trovafloxacin.