Doctors can write off label what what they want and frequently do. However they do so at their and their patients peril. Sometimes an MD may write"do not substitute" and the pharmacists will take it upon themselves to substitute nevertheless many times with little knowledge of indications or medical reason. However whatever the legality or economics of doing so are, the moral issue are important. As a thinking physician and cardiologist I would NEVER mislead a patient who trusts me to do the "right" thing by abrogating my ideals and prescribing him a clinically untested product however chemically similar the FD may certify it as being (biological vs.chemical similarity). If a physician prescribed a generic EPA ( or a pharmacist substituted it without specific MD permission) instead of Vascepa “off label” after a vascular event and lets say the patient upped and died the next month of an MI, the physician could be sued for malpractice on the basis of using a non-approved drug off label dangerously when there was a perfectly good FDA-approved RI INDICATION to use Vascepa. I believe the case would not be defensible and whether the insurance approved or allowed generic EPA would hold no water....even if the FDA said the 2 were chemically similar because the level of impurities the attention to prevention of oxidation in preparation etc could only ever be really demonstrated by placebo controlled real world clinical trial..period. Science matters all the rest is legalese and profiteering.