The Food and Drug Administration (FDA) sometimes issues a Boxed Warning on prescription medications, usually known as a Black Box Warning, for drugs that have a potentially serious side effect. Here is the Boxed Warning for Naltrexone:
Hepatotoxicity: Naltrexone has the capacity to cause hepatocellular injury when given in excessive doses. Naltrexone is contraindicated in acute hepatitis or liver failure, and its use in patients with active liver disease must be carefully considered in light of its hepatotoxic effects. The margin of separation between the apparently safe dose of naltrexone and the dose causing hepatic injury appears to be only five-fold or less. Naltrexone does not appear to be a hepatotoxin at the recommended doses. Patients should be warned of the risk of hepatic injury and advised to stop the use of naltrexone and seek medical attention if they experience symptoms of acute hepatitis.
Well, that certainly sounds concerning, doesn’t it? It’s important to know that this warning is based on one study in which 26 obese subjects were given naltrexone at five times the recommended dose for three weeks. Five of the 26 subjects showed elevations in liver enzymes associated with damage.
Of note, all of the enzymes returned to normal once the naltrexone was stopped. So, yes, like most substances, including water, things can go wrong if taken in excessive amounts.
This is the relevant question, and what anyone considering Naltrexone should want answered. Here’s what you’ll see a little further down on the same official FDA package insert (Caps are in the original):
NO CASES OF HEPATIC FAILURE HAVE EVER BEEN REPORTED.
NALTREXONE DOES NOT APPEAR TO BE A HEPATOXIN AT THE RECOMMENDED DOSES.
On one hand, there are all of the well-established dangers of alcohol and opioid dependence, and on the other hand there is the potential for reversible liver damage caused by taking an enormous and unheard of dose of a prescription drug intended to reduce alcohol and opioid use.
Does this Black Box Warning result in greater public safety or less?
If this warning discourages anyone from using naltrexone for his or her addiction, then the warning does more harm than good.