For Rhabdomyolysis; baseline creatinine phosphokinase (CPK) and creatinine should be measured before starting treatment. Treatment should be interrupted if rhabdomyolysis, any symptomatic CPK elevation or grade 4 asymptomatic CPK elevation occur. If they do not improve within 4 weeks discontinue treatment. If severity improves by at least 1 grade in 4 weeks restart treatment at 20mg daily. Vemurafenib can be continued during any changes to cometinib therapy.