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Naltrexone disposition in man after subcutaneous administration.
Drug Metabolism and Disposition: the Biological Fate of Chemicals
|November 1, 1984
Summary
This study tracked naltrexone metabolism and pharmacokinetics in males after subcutaneous administration. Results showed rapid absorption and excretion patterns similar to intravenous administration, with key metabolites identified.
Area of Science:
- Pharmacology
- Pharmacokinetics
- Drug Metabolism
Background:
- Naltrexone is an opioid antagonist used in addiction treatment.
- Understanding its pharmacokinetic profile after subcutaneous administration is crucial for therapeutic applications.
Purpose of the Study:
- To investigate the metabolism, excretion, and pharmacokinetics of [15,16-3H2]naltrexone following subcutaneous administration in human males.
- To compare these parameters with those observed after intravenous administration.
Main Methods:
- Six healthy human males received subcutaneous administration of naltrexone hydrochloride.
- Biological fluids were analyzed using high-performance liquid chromatography and liquid scintillation counting to measure radioactivity.
- Pharmacokinetic parameters including absorption and elimination rates, and half-lives were determined for naltrexone and its major metabolite, 6 beta-naltrexone.
Main Results:
- Naltrexone was rapidly absorbed, with a mean absorption half-life of 7.6 minutes.
- The elimination half-life for naltrexone was 1.68 hours, and for 6 beta-naltrexone was 8.8 hours.
- Approximately 76% of the administered dose was recovered in urine within 72 hours, with naltrexone and 6 beta-naltrexone found in both free and conjugated forms.
Conclusions:
- Subcutaneous administration of naltrexone leads to rapid systemic absorption.
- The metabolic and pharmacokinetic profiles are comparable to those seen with intravenous administration.
- Urinary excretion is a significant route of elimination for naltrexone and its primary metabolite.