Abuse deterrent opioid/opioid-antagonist transdermal patch

1. A transdermal patch comprising a multilaminate, said multilaminate comprising:

(i) a first layer comprising an opioid analgesic compound, or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable pressure sensitive adhesive;

(ii) a second layer comprising an opioid antagonist, or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable adhesive; and

(iii) a barrier layer disposed between the first and second layers, and wherein the barrier layer substantially prevents the opioid antagonist diffusing from the second layer to the first layer during use, and wherein the barrier layer is a microporous ultra high density polyethylene (UHDPE) material;

and wherein a proportion of the opioid antagonist in the second layer is present in the form of a pharmaceutically acceptable salt and a proportion of the opioid antagonist is present in a non-salt form.

2. A transdermal patch according to claim 1 , wherein 5-95% w/w or 30-70% w/w of the total opioid antagonist present in the second layer is in the form of a pharmaceutically acceptable salt and the remainder is in a non-salt form.

3. A transdermal patch according to claim 1 , wherein the opioid analgesic is selected from morphine, codeine, thebaine, diacetylmorphine (morphine diacetate; heroin), nicomorphine (morphine dinicotinate), dipropanoylmorphine (morphine dipropionate), desomorphine, acetylpropionylmorphine, dibenzoylmorphine, diacetyldihydromorphine, hydromorphone, hydrocodone, oxycodone, oxymorphone, ethylmorphine and buprenorphine, fentanyl, pethidine, levorphanol, methadone, tramadol and dextropropoxyphene.

4. A transdermal patch according to claim 1 , wherein the opioid analgesic is oxymorphone, or a pharmaceutically acceptable salt thereof.

5. A transdermal patch according to claim 1 , wherein the opioid analgesic is present at an amount of 1-10% w/w or 4-7% w/w in the first layer.

6. A transdermal patch according to claim 1 , wherein the opioid analgesic is present in a non-salt form.

7. A transdermal patch according to claim 1 , wherein the total amount of adhesive will constitute between 58 and 99% w/w of the first and second layers respectively.

8. A transdermal patch according to claim 1 , wherein the adhesive is selected from acrylate/polyacrylate materials, rubbers and silicones or mixtures thereof.

9. A transdermal patch according to claim 1 , wherein the adhesive is a mixture of an acrylate/polyacrylate adhesive and a silicone adhesive.

10. A transdermal patch according to claim 1 , wherein the first layer comprises a penetration enhancer.

11. A transdermal patch according to claim 10 , wherein the penetration enhancer is present in an amount of 2-12% w/w of the first layer.

12. A transdermal patch according to claim 10 , wherein the penetration enhancer is oleic acid.

13. A transdermal patch according to claim 1 , wherein the opioid antagonist in the second layer is selected from naltrexone (“NTX”), naloxone (“NLX”) or nalmefene.

14. A transdermal patch according to claim 1 , wherein the opioid antagonist is present in an amount of 1-20% w/w of the second layer.

15. A transdermal patch according to claim 1 , wherein the second layer further comprises polyvinylpyrollidinone in an amount of 0.5 to 15% w/w of the second layer.

16. A transdermal patch according to claim 15 , wherein the polyvinylpyrollidinone is polyvinylpyrollidone K30.

17. A transdermal patch according to claim 1 , wherein the second layer further comprises a cellulose component in an amount of 5 to 25% w/w of the second layer.

18. A transdermal patch according to claim 1 , wherein the second layer further comprises a hydrophilic material in an amount of 1 to 10% w/w of the second layer.

19. A transdermal patch according to claim 18 , wherein the hydrophilic material is propylene glycol or dipropylene glycol.

20. A transdermal patch according to claim 1 , wherein a proportion of the opioid antagonist in the second layer is present in the form of a pharmaceutically acceptable salt and a proportion of the opioid antagonist is present as a free base.

21. A method of treating a condition selected from the group consisting of opioid dependence, alcohol dependence, polydrug addiction, pain, cocaine addiction, eating disorders (e.g., binge eating) and treatment-resistant depression in a subject in need of such treatment, said method comprising administering a transdermal patch according to claim 1 to the skin of the subject.