How Long Do the Effects of Naltrexone Last?
The length of time naltrexone’s opioid-blocking effects last depends on whether you are prescribed oral or injectable naltrexone.
Oral Naltrexone
Oral naltrexone is typically prescribed as a once-daily tablet. The most common dosage is one 50 mg tablet daily, with effects that can last 24 to 36 hours. In some cases, your provider may determine that you need a higher dose of naltrexone, either 100 mg or 150 mg. The former will have effects lasting 48 hours, and the latter will last up to 72 hours.
Injectable Naltrexone
Injectable naltrexone is an extended-release formula that delivers opioid-blocking effects for four weeks.
Factors That Affect the Effectivity of Naltrexone
Naltrexone treatment can be highly effective, but it isn't necessarily the best treatment option for everyone. Some factors that can affect how effective naltrexone treatment is for you include:
How long ago opioids were last used
Naltrexone treatment should only be administered seven to 10 days after the last use of short-acting opioids and 10 to 14 days after the last use of long-acting opioids. If you take naltrexone too soon after opioid consumption, you can experience precipitated opioid withdrawal symptoms such as headache, nausea, vomiting, abdominal pain, and agitation.
Taking high doses of opioids
Although Naltrexone is effective at blocking the effects of other opioids, that effect can be overridden with high doses of opioids.
Whether naltrexone treatment is paired with therapy
Naltrexone was found to be more effective when paired with coping skills therapy that includes relapse prevention strategies and support for medication compliance.
How Long Does Naltrexone Stay in Your System?
When you receive treatment for opioid or alcohol use disorder, you may have concerns about traces of your naltrexone medication showing up in tests if your employer or another organization requires you to undergo drug or alcohol testing.
Although the effects of oral naltrexone last for one to two days, traces of your prescription can be detected in your system after the effects have worn off. How long naltrexone stays in your system depends on the type of test:
Urine
Naltrexone can only be detected in urine for four to six hours after you take your medication.
Saliva
A test can detect naltrexone in your saliva up to 24 hours after ingestion.
Blood
A blood test will show traces of naltrexone approximately three to four days after your last consumption.
Hair Follicle
Naltrexone can be found in a hair follicle test up to 90 days after use.
Several other factors can also impact how long naltrexone remains in your system:
- Age
- Physical activity
- Hydration
- Metabolism
- Weight
- Overall health
Generally, employers and other entities are looking for traces of alcohol or opioid drugs when administering drug tests. Naltrexone will not appear on these tests unless the test is specifically looking for naltrexone. If you have any concerns about your medication appearing on a mandatory drug test, you may wish to inform the organization beforehand about your treatment. You can also obtain a note from your provider regarding your prescription.
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