A 55-year-old man with severe depression is admitted after refusing food and fluids for several days. He understands that electroconvulsive therapy has been recommended because of the severity of his illness, can describe its likely benefits and memory-related adverse effects, and says repeatedly that he does not want it. He is not suicidal, psychotic or physically unstable, and his treating team considers medication and close nursing care acceptable alternatives for the present. Which one of the following is the most appropriate next step?