soporific
Concise Oxford English Dictionary © 2008 Oxford University Press:
soporific /ˌsɒpəˈrɪfɪk/
▶adjective inducing drowsiness or sleep.
■ sleepy.
▶noun a soporific drug or other agent.– derivatives
soporifically adverb.
soporifically adverb.
'soporific' also found in these Oxford entries:

