Related Clues:

• Endorphin, basically
• Den drug
• Medication
• H, e.g.
• Sedative substance
• Mind duller
• Smuggler's stock
• Anesthetize
• Religion, in an oft-quoted metaphor
• Stimulant's opposite
• Addictive stuff
• Painkiller since ancient times
• Doctor's prescription
• FDA part
• Psilocybin, for one