Abstract: Certain peptides which exhibit high selectivity for the kappa opioid receptor (KOR) versus the mu opioid receptor and little or no CYP3A4 inhibitory activity including tetrapeptides of four D-isomer amino acid residues having a C-terminus which is an N-oxide-substituted amide such, as H-D-Phe-D-Phe-D-Nle-D-Arg-NH-4-picolyl-N-oxide.

Abstract: Peptides which exhibit high selectivity for the kappa opioid receptor (KOR) and long duration of peripheral action without significant entry into the brain are created which are sequences of four D-isomer amino acid residues having a C-terminus which is a mono or di-substituted amide. Representative compounds, which have an affinity for the KOR at least 1,000 times their affinity for the mu opioid receptor and an ED.sub.50 of not greater than about 0.5 mg/kg, includeH-D-Phe-D-Phe-D-Nle-D-Arg-NHEt,H-D-Phe-D-Phe-D-Nle-D-Arg-morpholinyl,H-D-Phe-D-Phe-D-Nle-D-Arg-NH-4-picolyl,H-D-Phe-D-Phe-D-Nle-D-Arg-NHPr,H-D-Phe-D-Phe-D-Nle-D-Arg-thiomorpholinyl,H-D-Phe-D-Phe-D-Nle-D-Arg-NEt.sub.2,H-D-Phe-D-Phe-D-Nle-D-Arg-NHMe,H-D-Phe-D-Phe-D-Leu-D-Orn-morpholinyl,H-D-Phe-D-Phe-D-Nle-D-Arg-NHhEt,H-D-Phe-D-Phe-D-Nle-D-Arg-NH-cyclopropyl,H-D-Ala(2Thi)-D-4Cpa-D-Leu-D-Arg-morpholinyl,H-D-Phe-D-Phe-D-Nle-D-Arg-piperidinyl,H-D-Phe-D-Phe-D-Leu-D-Orn-NHEt,H-D-Phe-D-Phe-D-Leu-D-Lys-morpholinyl,andH-D-Phe-D-Phe-D-Nle-D-Arg-piperazinyl.

Abstract: Novel vasotocin derivatives having an inhibitory effect on uterine contractions, pharmaceutical compositions containing these derivatives, and the use thereof in the therapeutical treatment of excessive muscle contractions in the uterus and described. The derivatives differ from vasotocin in that the structure of the original hormone has been modified at positions 1, 2 and, optionally, 4 and/or 8. The vasotocin derivatives thus have the formula ##STR1## wherein Mpa is a 3-mercaptopropionoyl residue (--S--CH.sub.2 --CH.sub.2 --CO--);A is the peptide residue of L- or D-tyrosine-O-ethyl ether (in other words, 4-ethoxy-L or D-phenyl alanine, i.e.