SOPORIFIC

causing drowsiness

tending to induce sleep

/NOUN a drug that induces sleep
SYN - hypnotic

ADJ - sleep inducing
SYN - hypnogic, somniferous

Inducing mental lethargy
SYN - narcotic
ANT - stimulative

"Knowing that he would need to be on top of his game later in the day he made sure to stay away from anything soporific."

"He purposely didn't eat turkey because of its soporific qualities."

"It was rare that she understood or took in anything when she attended the teacher's soporific lectures."