The structurally related neuropeptides, substance P (SP), neurokinin A (NKA
), and neurokinin B (NKB), which belong to a family of molecules termed tac
hykinins and are widely distributed in the central and peripheral nervous s
ystems, influence the function of many tissues. SP and NKA have links to th
e following chronic diseases: asthma, inflammatory bowel disorders, rheumat
oid arthritis, pain and psychiatric disorders. These peptides exert their e
ffects through three G-protein coupled receptor subtypes, namely, the NK1,
NK2, and NK3 receptors. Non-peptide antagonists of these receptors may prov
ide opportunities for disease treatments. In this review, the very recent a
dvances in nonpeptide neurokinin receptor antagonists will be described wit
h an emphasis on structure-activity relationships which have been developed
.