I admit to some pre-existing bias against the medication. I’m not certain, to be honest, whether that bias was based upon sound clinical reasoning, or whether it was based on personal, negative reactions to naltrexone in my past. Or maybe, as a recovering opioid addict, I have negative feelings about anything that blocks mu receptors!
Vivitrol consists of naltrexone in a long-acting matrix that is injected into the gluteal muscle each month. The medication is expensive, costing about $1000 per dose (!) That cost is usually covered by insurance, and like with Suboxone, Wisconsin Medicaid picks up the tab save for a $3 copay. Alkermes, the company that makes Vivitrol, also has a number of discounts available to reduce or even eliminate any copays required by insurance companies.
I’ll leave the indication of Vivitrol for alcoholism for another post. The indication for opioid dependence came more recently, and appears more obvious, given the actions of naltrexone at the mu opioid receptor.
In short, naltrexone blocks the site where opioids—drugs like oxycodone, heroin, and methadone—have the majority of their actions. Blockade of that site prevents opioids from having any clinical effect. There is some dose, of course, where an agonist would regain actions— an important feature in the case of surgery or injury. But even in those high doses, the euphoric effects of addictive opioids would be muted. People on Vivitrol, essentially, are prevented from getting high from opioids.