Kinetics of a naltrexone sustained-release preparation

Area of Science:

• Pharmacology
• Biomaterials Science
• Drug Delivery Systems

Background:

• Naltrexone is an opioid antagonist used in addiction treatment.
• Developing sustained-release formulations can improve patient compliance and therapeutic efficacy.
• Biodegradable polymers offer a promising matrix for controlled drug delivery.

Purpose of the Study:

• To evaluate the pharmacokinetic profile of a biodegradable sustained-release naltrexone bead preparation.
• To assess the safety and tolerability of the naltrexone bead formulation.
• To determine the absorption characteristics of naltrexone following subcutaneous implantation of the beads.

Main Methods:

• Three male subjects received intravenous naltrexone hydrochloride and subcutaneous implantation of naltrexone beads.
• Plasma and urine naltrexone and naltrexol levels were monitored over time.
• Pharmacokinetic parameters including clearance and half-life were estimated.

Main Results:

• Intravenous naltrexone kinetics showed a plasma clearance of 3.1–3.4 L/min and a half-life of 1.7–3.7 hours.
• Following bead implantation, plasma naltrexone levels were maintained at 0.3–0.4 ng/mL for approximately one month.
• Estimated absorption after bead implantation ranged from 70% to 77% with minor tissue irritation observed in two subjects.

Conclusions:

• The biodegradable naltrexone bead preparation provides sustained drug release for approximately one month.
• The formulation appears to be well-absorbed and generally well-tolerated, with potential for long-term naltrexone delivery.
• Further studies are warranted to confirm efficacy and safety in a larger population.