For a drug that binds to the same receptors that addictive drugs and opioids bind to, a justifiable question can come to mind: is naltrexone addictive?

Fortunately, naltrexone isn’t addictive. It comes with a list of side effects, some of which can be serious. However, because of its mechanism of action, naltrexone won’t lead to physical dependence.

Understanding Naltrexone’s Mode of Action: Does It Make the Drug Addictive?

Naltrexone is a medication that doctors prescribe to their patients who suffer from opioid or alcohol addiction. It’s an opioid antagonist that blocks the effects of addictive opioids like heroin, oxycodone, and morphine.

Naltrexone blocks opioid receptors in the brain. These receptors are where addictive drugs bind to and cause the euphoric effects.

By attaching to these receptors and stimulating a transient euphoric and sedative effect, the patient may unnecessarily use this drug despite not having a medical problem just to get that sensation back.

When naltrexone binds to those opioid receptors, consuming the addictive opioid will have a drastically less potent effect on the patient.

Is Naltrexone Addictive?

Naltrexone stops opioids from binding to their receptors by binding itself to them. Doesn’t that make it addictive? The answer is no.

Despite binding to said receptors, naltrexone doesn’t fully activate them. Instead, it blocks them. In other words, taking naltrexone doesn’t produce the pleasurable sensation the patient gets from abusing opioids.

As such, the patient won’t feel the need to take naltrexone nor have any withdrawal side effects after stopping the drug use. Unlike opioids and other addictive drugs, naltrexone (under the doctor’s supervision) can be stopped abruptly without issues.

Can You Overdose on Naltrexone?

Consuming naltrexone doesn’t activate the opioid receptors, but can you overdose on it?

Unlikely. Naltrexone has a high therapeutic index, meaning the lethal dose is quite high. Patients also don’t get any pleasure from using naltrexone, which makes it unlikely for a patient to want more of it.

However, since naltrexone prevents the pleasurable effect of opioids, the patient might get an opioid overdose while trying to satisfy their opioid cravings.

Side Effects of Naltrexone

Despite not being addictive, naltrexone has a list of side effects that make it a drug to be handled with care.

Naltrexone’s common (but less severe) side effects include:

  • Toothache
  • Cold symptoms (pain in the head and joints)
  • Trouble falling asleep
  • Muscle cramps
  • Nausea and vomiting
  • Occasional dizziness
  • Loss of appetite

Except for nausea and vomiting, all of these side effects are somewhat bearable. Both nausea and vomiting will also subside gradually the more you get used to the drug.

Still, despite not being serious, you should report the side effects you’re experiencing to your doctor.

Unfortunately, naltrexone can cause some serious side effects that include:

  • Face and eye swelling
  • Skin rash, blisters, lumps, and open wounds at the site of injection
  • Yellowing of eyes
  • Persistent stomach pain
  • Dark urine

While these side effects are fairly less common, you should immediately inform your doctor if you experience any of them.

Note: Naltrexone treatment should start after the opioid withdrawal symptoms have subsided. Otherwise, it’ll increase the duration of these symptoms.


Naltrexone competes with opioids over the same brain receptors and doesn’t fully activate them when it binds to them. That’s why it reduces the effects of addictive drugs without being addictive itself.

However, care should be taken while taking naltrexone, as it has a considerable list of side effects. It’s important to keep track of such effects if possible and to keep your doctor in the loop.

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