Nonimmediate Hypersensitivity Reaction to Rifaximin Confirmed With a Drug Challenge Test

J Investig Allergol Clin Immunol 2021; Vol. 31(5): 446-460 © 2021 Esmon Publicidad pustules, mucosal involvement, skin hyperpigmentation, or desquamation. Her skin lesions resolved spontaneously 7 days after discontinuation of rifaximin. After obtaining the patient’s written informed consent, we performed an allergological work-up, including skin prick test (SPT) and a graded DCT with rifaximin. SPT was performed with rifaximin at 1 mg/mL on the volar aspect of the forearm and yielded a negative result [6]. On the same day, the patient underwent a DCT, consisting of a graded oral challenge starting at 50 mg and followed by 150 mg 30 minutes later, up to a final dose of 200 mg. One hour after the DCT, the patient felt nauseous, with diarrheic stool that resolved spontaneously without medication. The DCT was considered inconclusive and repeated 24 hours later. Three hours after completion of the second DCT, the patient again experienced diarrheic stools. Ten hours after the DCT, she developed a maculopapular erythematous and pruritic skin rash on her abdomen and left arm (Figure). She was treated with oral prednisone 0.5 mg/kg/d for 3 days and loratadine 10 mg/d for 7 days until the skin lesions resolved, without desquamation or residual lesions. The rationale for an allergological study with rifaximin was that the patient had a long history of gastrointestinal infections, in which rifaximin is an effective first-line therapy. Although reactions to rifamycins (eg, fever, rash, flu-like syndrome, acute renal failure, hemolytic anemia, thrombocytopenia, and anaphylaxis) have been reported [7], few reactions to rifaximin have been described since it was approved [3,4]. In the present case, the patient initially developed gastrointestinal symptoms 3 hours after receiving the first dose of rifaximin; these were considered a nonimmune adverse reaction to rifaximin. She continued treatment, developing a mild maculopapular Nonimmediate Hypersensitivity Reaction to Rifaximin Confirmed With a Drug Challenge Test