Implantable technology for long-term delivery of nalmefene for treatment of alcoholism

Pharmacotherapy treatment for alcoholism is limited by poor compliance, adverse effects, and fluctuating drug levels after bolus administration. A long-term delivery system would improve upon these limitations. The current study describes the characterization of a sustained release implant containing nalmefene, an opioid antagonist, for treatment of alcoholism. Nalmefene was blended with ethylene vinyl acetate (EVA), extruded into 2.8 mm x 27 mm rods, and coated with EVA to optimize release. In vitro release was determined by HPLC, and in vivo release characteristics after subcutaneous implantation into rats were determined by LC-MS/MS analyses. Extrusion produced rods containing 80.09 +/- 6.0 mg nalmefene. In vitro release was high from the uncoated rods, and they were depleted of drug fairly quickly; however EVA coatings maintained release over longer periods. The 25 wt.% coated rods provided in vitro release of 0.36 mg/day/rod, and in vivo release of 0.29 mg/day/rod over 6 months, and showed dose-dependent nalmefene plasma concentrations (one rod: 3.33 +/- 0.56 ng/ml, three rods: 10.19 +/- 2.31 ng/ml). After explantation, nalmefene plasma concentrations were undetectable by 6 h. A sustained release nalmefene rod provides 6 months of drug with no adverse effects.