Possible increased risk of infections, including reactivation of latent chronic infections. Avoid use in clinically important infections (use with caution in chronic infection or history of recurrent infections). Risk of malignancies may be increased in patients receiving immunosuppressive agents (use cautiously in patients at high risk for malignancy or in those with history of malignancy). Patients receiving other immunosuppressive agents should not receive concurrent therapy with efalizumab. Risk of thrombocytopenia or hemolytic anemia. Progressive multifocal leukoencephalopathy reported with efalizumab use. Worsening of psoriasis can occur during or following discontinuance of efalizumab therapy. Hypersensitivity reactions (e.g. angioedema, asthma, dyspnea, maculopapular rash, urticaria) reported. Arthritic episodes reported, including new-onset or recurrent severe arthritis and psoriatic arthritis. Do not administer acellular, live, or live-attenuated vaccines during efalizumab therapy. Possible development of predominantly low-titer antibodies to efalizumab or other protein components of the preparation. Use with caution in geriatric individuals due to increased incidence of infections. Produced in a Chinese hamster cell medium.