 Serious rashes can develop in rare cases, and require immediate medical attention due to the possibility of Steven's-Johnson Syndrome, or other hypersensitivities to armodafinil.The mechanism of action of armodafinil is unknown.Armodafinil ("R"-(−)-modafinil) has pharmacological properties almost identical to those of modafinil (a mixture of "R"-(−)- and ("S")-(+)-modafinil).