WASHINGTON — Veterans and their advocates slammed a new rule by the Department of Veterans Affairs for determining disability compensation, predicting it will lower their payments for service-related illnesses and injuries. The rule, effective immediately, states that a disability level must be based on how well a veteran functions while on medication and not on the underlying impairment itself. Titled “Evaluative Rating: Impact of Medication,” the interim final rule was published in the Federal Register and affects how the VA rates a veteran’s disability for new claims and when reevaluating disabilities through clinical