Review of reviews.
D000700:Analgesics / Q000494:pharmacology; D000818:Animals; D055598:Chemical Phenomena; D002621:Chemistry; D004723:Endorphins; D006801:Humans; D010600:Pharmacology; D008517:Phytotherapy; D019966:Substance-Related Disorders
D000700:Analgesics; D004723:Endorphins