An open-label, phase 3 study of the safety of the O’Neil Long Acting Naltrexone Implant treatment for substance dependence

The primary objective is the assessment of the safety of O'Neil Long-Acting Naltrexone Implants for the treatment of substance dependence both during and after its treatment effects have diminished. Patients will be treated with naltrexone implants. Naltrexone implants ("O'Neil Implant") consisting of naltrexone loaded poly [trans- (DL)lactide microspheres compressed into tablets with a poly(DL)lactide coating will be inserted into the lower abdomen through a small (approximately 7mm) incision under local anaesthetic as a one-off procedure at commencement of the 12-month study. Each implant’s total weight is approximately 3.1 g with a naltrexone drug loading of 60%. Patient retreatment during the 12-month study is allowed following return to regular heroin use defined as greater than 3 times per month, or in the event of attendance to accident and emergency or hospitalisation for accidental opioid overdose. Persons weighing under 63 kg will be treated by insertion of two, and those over 63kg by insertion of three naltrexone implants.