A patient with RRMS (relapsing remitting multiple sclerosis) developed rhabdomyolysis and increased CK during IFNβ1a (interferonbeta1a) therapy.

Be aware of the possibility of rhabdomyolysis during IFNβ1a therapy.

CK (creatine kinase) activity should be measured to prevent rhabdomyolysis during IFNβ1a therapy.

If patients with MS complain of severe myalgia CK activity should be measured.

Increase in CK could be an adverse effect of IFNβ1a therapy.