Only a few of these patients had a history of prior hypersensitivity reactions. Allergic reactions of varying severity, including anaphylactic shock and anaphylactoid reactions, have occurred in patients receiving grepafloxacin. Grepafloxacin should be discontinued if an allergic reaction or any other sign of hypersensitivity appears. Serious acute hypersensitivity reactions require immediate treatment. Serious and sometimes fatal events of uncertain etiology have been reported in patients receiving therapy with quinolones.
Serious events are extremely rare and generally occur following administration of multiple doses.
The efficacy of grepafloxacin for treatment of syphilis is not known. Antimicrobial agents used in high doses for short periods of time to treat gonorrhea may mask or delay the symptoms of incubating syphilis. All patients with gonorrhea should have a serologic test for syphilis at the time of diagnosis. Patients treated with grepafloxacin should have a follow-up serologic test for syphilis 3 months after treatment for gonorrhea. Pseudomembranous colitis has been reported with nearly all antibacterial agents, including quinolones, and may range in severity from mild to life-threatening.