The Other Opioid Dependence Medication

Today I met with representatives from Alkermes who were promoting Vivitrol, a long-acting mu opioid antagonist that is indicated for treatment of alcoholism and opioid dependence.

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.
Back in my using days, I took naltrexone, thinking that doing so would help me get ‘clean.’  I didn’t wait long enough, however, and so I became very sick with precipitated w/d.  The makers of Vivitrol recommend waiting at least a week, after stopping opioids, before getting an injection of Vivitrol.  I suspect that a week is not long enough to prevent w/d, but I realize that it would be very difficult to expect patients to last longer, without using anything.  I would expect that any precipitated w/d could be reduced through use of comfort medications, at least for a day or two until the symptoms are mostly gone. This requirement, though, to be clean for a week or more is one of my problems with the medication.
As an aside, I was also prescribed naltrexone (oral tabs) at the end of my three months in residential treatment, and I took the medication for another three months.  I had no withdrawal or other side effects to naltrexone at that time.
Another issue was the concern that naltrexone has been connected to hepatic toxicity.  We discussed that issue today, including the studies that led to that connection—which are not compelling.  The discussion allayed most of my concerns about liver problems from Vivitrol.
Finally, I have always recommended buprenorphine over naltrexone because of the anti-craving effects of buprenorphine that result from the ‘ceiling effect’ of the medication.  I worried that naltrexone, by blocking the actions of endorphins, would actually increase cravings.  But that is not what the data shows.  In the studies with Vivitrol, cravings for opioids were dramatically reduced by the medication.  The mechanism of that effect is not entirely clear;  some of the anti-craving effect may be psychological, as addicts stop wanting something when they know there is no way to get it.  But there may be other complicated neurochemical effects at presynaptic opioid receptors that are not fully understood.
The bottom line is the result of treatment;  the very sick opioid addicts treated in the studies used by Vivitrol to gain FDA approval showed a profound reduction in opioid-positive urines, over a span of 6 months.
I suspect that I will continue to favor buprenorphine.  I do not buy into the ‘need’ some people describe to ‘get of buprenorphine as fast as possible.’  Buprenorphine is a very effective, safe, long-term treatment for inducing remission of opioid dependence.  But because of the cap, I am glad that another option is available to treat this potentially-fatal condition.  And I admit to perhaps being too quick to judge Vivitrol, which appears to be a safe alternative—particularly for people who have a lower opioid tolerance that do not want to push it higher, or for people who have been free of opioids for a week or two.
I would invite local people who are on my buprenorphine waiting list to consider Vivitrol as an option.