The present invention provides peptides capable of sustaining antagonist activity against substance P for long periods of time. A peptide selected from (a) to (d) can sustain antagonist activity against substance P, analgesic activity, and anti-inflammation activity for a long period of time: (SEQ ID NO: 3) (a) Ala-Tyr-Gln-Leu-Glu-His-Thr-DTrp-Gln-Gly-Leu- Leu-NH2; (b) a peptide consisting of a partial sequence of (a), which consists of 6 to 11 consecutive amino acids comprising at least the C-terminal Thr-DTrp-Gln-Gly-Leu-Leu-NH2 (SEQ ID NO: 18); (c) Ala-Tyr-Gln-Leu-Glu-His-Thr-Phe-Gln-DTrp-Leu-Leu-NH2 (SEQ ID NO: 4); and (d) a peptide consisting of a partial sequence of (c), which consists of 6 to 11 consecutive amino acids comprising at least the C-terminal Thr-Phe-Gln-DTrp-Leu-Leu-NH2 (SEQ ID NO: 8).