Do not administer as bolus inj. Increased risk of PML. Do not perform anti-JCV Ab testing w/in 2 wk of plasmapheresis/plasma exchange due to removal of Ab from the serum or w/in 6 mth of IVIg. Consider more frequent MRI (eg, 3-6 mthly basis) in patients who have all 3 risk factors for PML (anti-JCV Ab positive, received >2 yr of therapy & prior immunosuppressant therapy) or those w/ high anti-JCV Ab index who have received >2 yr of therapy & w/o prior history of immunosuppressant therapy. Frequently monitor patients switching from DMTs w/ an immunosuppressant effect. Consider differential diagnosis in any patient w/ multiple sclerosis taking Tysabri, who presents w/ neurological symptoms &/or new brain lesions in MRI. Permanently discontinue treatment if PML develops. Monitor for development of immune reconstitution inflammatory syndrome. Discontinue use if infections including opportunistic infections (eg, encephalitis & meningitis) develops. Screen for acute retinal necrosis in patients presenting w/ eye symptoms eg, decreased visual acuity, redness & painful eye. Discontinue administration at the 1st symptoms or signs of hypersensitivity. Concurrent or prior treatment w/ immunosuppressants. Potential concomitant immune effects when switching patients from teriflunomide. Not recommended to initiate treatment after alemtuzumab therapy. Evaluate presence of Abs & discontinue treatment if these remain positive in a confirmatory test after at least 6 wk. Patients on controlled Na diet. Monitor for signs & symptoms of liver injury (eg, jaundice & vomiting). May affect ability to drive & use machines. Pregnancy. Discontinue use during lactation. Childn & adolescents ≤18 yr. Not recommended for use in elderly >65 yr.