RT Book, Section A1 Katzung, Bertram G. A1 Kruidering-Hall, Marieke A1 Tuan, Rupa Lalchandani A1 Vanderah, Todd W. A1 Trevor, Anthony J. SR Print(0) ID 1180556894 T1 Opioid Analgesics & Antagonists T2 Katzung & Trevor's Pharmacology: Examination & Board Review, 13e YR 2021 FD 2021 PB McGraw-Hill Education PP New York, NY SN 9781260117127 LK accesspharmacy.mhmedical.com/content.aspx?aid=1180556894 RD 2024/03/28 AB The opioids include natural opiates and semisynthetic alkaloids derived from the opium poppy, pharmacologically similar synthetic surrogates, and endogenous peptides. On the basis of their interaction with several opioid receptors (μ [mu], δ [delta], and κ [kappa] receptors), individual drugs are classified as agonists, mixed agonist-antagonists, and antagonists at one or more of these receptors. Because of their euphoric effects, μ-opioid agonists are important drugs of abuse and are responsible for severe personal and social problems.Opioid peptides released from nerve endings modulate neurotransmission in the brain, spinal cord, and in primary afferents via their interaction with one or more of the above opioid receptors.