soporiferous

adj

1. (archaic)soporific, sleep-inducing

   “And she poured from a golden urn, into a cup of the same metal, the sombre-coloured beverage which she had mingled with the soporiferous juice of the nepenthe.”

   “At last the soporiferous fumes of the wine lulled him into a gentle repose.”

   “All this I was told; for, while the whole operation was performing, I lay in a profound sleep, by the force of that soporiferous medicine infused into my liquor.”