A Case of Atypical Delayed Anaphylaxis to Rifampin

Rifampin is a mainstay in anti-tuberculosis therapy and is generally well tolerated and safe to take at therapeutic dosing. While anaphylactic reactions to rifampin are exceedingly rare, prompt recognition and awareness is vital to patient safety, and alternative medications should be considered desensitization has been associated with significant morbidity. Here we report a case of a severe anaphylactic reaction to rifampin. A 65-year-old Asian woman was diagnosed with active tuberculosis and initiated on rifampin, isoniazid, pyrazinamide, and ethambutol (RIPE). A couple of weeks after initiating RIPE therapy, she developed urticaria and angioedema and therapy was held. Upon resumption of RIPE, she developed emesis, fever, chills, perioral cyanosis, and hypotension within a few hours of the first dose. She was admitted to the intensive care unit for a rifampin graded dose challenge and subsequently developed a severe anaphylactic reaction to rifampin four hours after the final dose of the challenge. She tolerated desensitization to isoniazid and ethambutol well and was prescribed an alternative anti-tuberculosis regimen of isoniazid, ethambutol, levofloxacin, and pyridoxine for a total of 18 months to complete her treatment