Naloxone-6α-spirohydantoin: A long-acting opiate antagonist

We have synthesized a novel derivative of naloxone, naloxyl-6α-spirohydantoin. The compound was rigorously purified and its stereochemical structure characterized. In tests in vivo in mice, it was less toxic than the parent compound and it showed weak anticonvulsive activity. It exerted antagonist effects comparable to those of naloxone but its effects were longer lasting, persisting for a week.