The dermorphin-derived peptide [Dmt1] dermorphin analog labels m-opioid receptors with high affinity and selectivity in receptor binding assays. In mice, radiant heat tail-flick assays, [Dmt1] dermorphin analog produces profound spinal and supraspinal analgesia, being approximately 5000 and 100 times more potent respectively than morphine in causing these analgesia on a molar basis. When administered systemically, [Dmt1] dermorphin analog has been shown to be over 200 times more potent than morphine.