Naltrexone is a narcotic antagonist used in opioid overdose. It is injected intravenously or intramuscularly. It travels through the blood to the target cells in the naltrexone pathway and to the liver. It is transported into the liver by an organic cation transporter. In the liver naltrexone is metabolized into 6-beta-naltrexol. It was predicted by biotransformer that Cytochrome P450 2C9 metabolizes naltrexone into 6-beta-naltrexol. However, it has also been found that Naltrexone in certain doses inhibits cytochrome enzymes. Only 2% of naltrexone remains as the original naltrexone while the remainder is metabolized into 6-beta-naltrexol and other minor metabolites. Naltrexone and 6-beta-naltrexol are transported out of the liver by organic cation transporters into the blood. It is then transported to the kidney where it is excreted renally. 53% to 79% of the dose is excreted as metabolites. A minor amount goes through bile to be excreted through the feces.

Naltrexone Metabolism References