When a vampire drinks the blood of the dead, the effect is a reaction opposite to that of drinking the blood of the living. The dead blood sickens a vampire to the point of paralysis, making the vampire appear corpse-like. This happens to Lestat when Claudia, in an attempt to kill her maker, tricks him into drinking the dead blood of a young boy. He lies on the carpet of their Rue Royale townhouse, staring helplessly at the ceiling, shuddering, his eyes veiling, barely able to form a coherent cry for help to Louis, utterly susceptible to the kitchen knife that Claudia uses to cut his throat before plunging it into his chest.
The dead blood phenomenon appears in Interview with the Vampire (1976). For more perspectives on dead blood, read the Alphabettery entries Claudia, Lestat de Lioncourt, and Louis de Point du Lac.