This invention relates to crystalline salts of naloxone and of naltrexone and their use as opioid antagonists. The crystalline salts of the invention include naloxone saccharinate, naltrexone succinate and a methanol solvate of naltrexone succinate. A drug-in-adhesive transdermal patch containing the opioid analgesic fentanyl or an analog thereof and a crystalline salts of naloxone or naltrexone is disclosed. Also disclosed is a method of treating pain, such as acute, chronic or intermittent pain, by applying a drug-in-adhesive transdermal patch of the invention to the skin of a patient in need thereof.
