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Dr. Mark
Dr. Mark, Physician / Surgeon
Category: Medical
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Experience:  U.S. Surgeon / Neurological Surgery
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How long does Naltrexone 50 mg stay in your system I am on

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How long does Naltrexone 50 mg stay in your system? I am on this medication for a medical condition. I am having a pre-employment drug test done and have read that naltrexone can cause a false positive result for opiates. I want to ensure I schedule the drug screening appropriately so I do not receive a false positive result. Thank you.
If you have a valid prescription for the medication, you can let the people doing the drug test know, so they can alert the lab that you are taking the medication -- thus a "false" positive screen would be recognized.

Regardless, the detection of drugs relies on the amount of drugs that are left in the system. Naltrexone has a half-life of 4 hours, or every 4 hours, 50% of the drug is eliminated. So at 24 hours, over 95% of the drug has been eliminated. So holding off a couple of days should essentially eliminate the drug from your system.

Of course, if you're taking it for a medical condition, it's best to get a letter from your doctor stating this, so that there is no problem with the drug screen.
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