This invention relates to cocrystals of naloxone and of naltrexone and thier use as opioid antagonists. The cocrystais of the invention include naloxone isonicotinamide cocrystal, naloxone hydrochloride piperazine cocrystal, naltrexone menthol cocrystal, naltrexone thymine cocrystal, naltrexone 2,5-dihydroxybenzoic acid cocrystal, naltrexone salicylic acid cocrystal, naltrexone hydrochloride piperazine cocrystal and naltrexone hydrochloride sulfathiazole cocrystal. A drug-in¬ adhesive transdermal patch con taining the opioid analgesic fentanyl or an analog thereof and a cocrystal 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. Also disclosed is an improved transdermal patch for administering fentanyl or an analog thereof, or for administering a mu opioid agonist, the improvement wherein the transdermal patch contains a cocrystal of the invention in an abuse limiting amount. The improved transdermal patch may be a drug-in-adhesive transdermal patch or a reservoir transdermal patch.La présente invention concerne des co-cristaux de naloxone et de naltrexone et leur utilisation comme antagonistes des opioïdes. Les co-cristaux de l'invention comprennent un co-cristal de naloxone et d'isonicotinamide, un co-cristal de chlorhydrate de naloxone et de pipérazine, un co-cristal de naltrexone et de menthol, un co-cristal de naltrexone et de thymine, un co-cristal de naltrexone et d'acide 2,5-dihydroxybenzoïque, un co-cristal de naltrexone et d'acide salicylique, un co-cristal de chlorhydrate de naltrexone et de pipérazine et un co-cristal de chlorhydrate de naltrexone et de sulfathiazole. L'invention concerne un timbre transdermique avec un médicament inclus dans l'adhésif, contenant l'analgésique opioïde fentanyle ou un analogue de celui-ci et un co-cristal de naloxone ou de naltrexone. L'
