Year 2013-The FDA has added a new black box warning to 2 drugs, rituximab (Rituxan) and ofatumumab (Arzerra) for the potential of either drug to cause reactivation of hepatitis B virus (HBV) as well as fulminant and fatal HBV infection in HBV carriers who have not had any prior instances of HBV virus activation.   The mac contractor may tell you this is not reasonable and necessary for rheumatoid arthritis and autoimmune encephalitis.