Adverse effects of rifamycin
No severe adverse effects were observed in clinical trials with rifaximin. There have been a few postmarketingeports of hypersensitivity reactions, including allergic dermatitis, rash, angioneurotic edema, urticaria and pruritus. The drug is contraindicated in patients who are allergic to rifamycins. It has not been studied in pregnant women, but was teratogenic when given orally to animals at doses 2 to 33 times the usual human oral dose adjusted for body surface area.