A substance or medication that relieves pain; a pain-relieving agent or analgesic.
From Greek a- (without) + algos (pain) + -gen (producing). An analgen is something that produces a state without pain.
This is a somewhat archaic term for painkillers—you're more likely to hear 'analgesic' today, but 'analgen' appears in older medical texts and shows how terminology for drugs has evolved.
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