Novel Endomorphin Analogs are More Potent and Longer Lasting Analgesics in Neuropathic, Postoperative, Inflammatory, and Visceral Pain Relative to Morphine.

•Novel endomorphin analogs with reduced adverse effects alleviated multiple forms of pain.•Neuropathic, inflammatory, postoperative, and visceral pain were effectively relieved.•Intrathecal injection produced more potent and longer-lasting relief than morphine.•Intravenous injection equal or greater potency and longer-lasting relief than morphine.