Welcome Back, Kotter S03E22 - What Goes Up

Freddie is prescribed painkillers to treat a nagging injury he suffered playing basketball ... and soon becomes hooked. His friends become concerned about Freddie's increasingly scary behavior, but "Boom-Boom" tries to brush them off - after all, it's just "vitamins." What becomes even more scary is that Horshack blindly believes his friend's explanation, even though it becomes clear that Freddie needs help before something goes horribly wrong.