Buprenorphine + naloxone: new combination. Opiate dependence: no proof of reduced risk of self-administered injection.

(1) Two drugs with similar efficacy are available in France for heroin replacement therapy: methadone and buprenorphine. (2) Buprenorphine is sold in the form of sublingual tablets, but some patients dissolve and inject them. Methadone is the main alternative for these patients. Other intravenous opiate derivatives can also be tried, although they have not been approved for this indication. (3) In order to help prevent patients from injecting themselves with buprenorphine, a sublingual combination of buprenorphine + naloxone is to be marketed in France. (4) From a pharmacological point of view, this combination makes sense. Naloxone, an opiate antagonist, is very poorly absorbed with sublingual administration, but if it is injected intravenously, it will antagonise the effects of buprenorphine. However, clinical studies are needed to determine whether or not this prevents injection. (5) A double-blind trial in 326 patients compared replacement therapy with buprenorphine 16 mg + naloxone 4 mg/day versus buprenorphine 16 mg + placebo. The addition of naloxone did not reduce the efficacy of sublingual buprenorphine, but the frequency with which patients injected the drugs was not studied in this trial. (6) This combination of buprenorphine + naloxone has not been directly compared with methadone. (7) In addition to the classical adverse effects of opiates, buprenorphine can cause hepatic adverse effects. (8) Little evidence is available on the effects of intravenous injection of buprenorphine + naloxone. According to an epidemiological survey conducted in Finland, where the combination is also marketed, about 8% of patients regularly inject it intravenously. (9) Patients who are likely to inject buprenorphine should be switched to methadone.