additional drugs, not specifically licensed for psoriasis, have been found to be effective . These include the antimetabolites tioguanine , mercaptopurine and fluorouracil , the cytotoxic agents hydroxyurea and paclitaxel , alkylating agents chlorambucil and cyclophosphamide , some DMARDs like sulfasalazine , colchicine , dapsone , the immunosuppressants mycophenolate mofetil ,