It was included in an anthology I read in the 90’s.
Basically Bela Lugosi is filming Dracula and at the end of a long day, he gets high on morphine and hallucinates meeting Vlad Tepes.
This sounds very much like Much at Stake, a short story by Kevin J. Anderson first published in 1991. It has been anthologised various times, notably in The Ultimate Dracula (also published in 1991).
The story begins with Lugosi filming Dracula at Universal Studios. After a long day he takes some morphine to relax:
After making certain he had closed his dressing room door, Lugosi filled the syringe with morphine. His legs tingled, trembled, aching for the relief the drug would give him.
but instead finds himself transported to meet the original Vlad the Impaler (Vlad Tepes).
Startled, Lugosi turned around, then back to face the stranger who had frightened him. "Who are you?" he asked. The Hungarian words fit naturally in his mouth...
The haunted stranger took a hesitant step toward Lugosi. "I am . . . Vlad Dracula. I bid you welcome. I have waited for you a long time."