"I could." Slowly. "But it would be a bad way to do it, both in terms of effectiveness in alleviating the symptoms and in terms of the dependency that's causing them. Treating them with morphine would ... well, it'd be counterproductive in the long run."

If the conversation were less charged with tension, he might try saying something like have you ever tried drinking more to cure a hangover? As it is ... lightness doesn't seem appropriate.