Fentanyl withdrawal

Here we have to be honest about the limits of the evidence. No US public health agency publishes a firm, fentanyl-specific timeline.

Fentanyl is a short-acting opioid. General guidance for short-acting opioids puts the start of withdrawal at 8 to 24 hours after the last dose, lasting 4 to 10 days. Many people who use fentanyl daily report feeling sick sooner than that.

There is a second wrinkle. Researchers believe that with regular use, fentanyl builds up in body fat and is released slowly. So fentanyl can linger in the body after the last dose, even while withdrawal is under way.

In practice, this means your experience may not match the standard withdrawal timeline. It may start sooner, and it may drag on longer.

Buprenorphine is one of the main medicines for opioid use disorder. It works by attaching to the same receptors in the brain that other opioids use.

It holds on to those receptors very tightly, but it activates them only partly. If you still have a lot of another opioid in your system, buprenorphine pushes it off the receptors and replaces a strong signal with a weaker one.

Your body reads that sudden drop as withdrawal, all at once. This is precipitated withdrawal. NIDA describes it as a rapid onset of aches, nausea, vomiting, diarrhea and cramps that can occur within two hours of the first dose.

With heroin or pain pills, waiting until ordinary withdrawal has started is usually enough to avoid it. With fentanyl, because the drug may linger, some people get precipitated withdrawal even after waiting.

It is temporary and it can be treated. It is also frightening, and it puts some people off buprenorphine for good. That is a loss, because the medicine works.

The risk is real, but it should not be overstated. In a NIDA-funded study of about 1,200 people starting buprenorphine in emergency departments, most of whom used fentanyl, precipitated withdrawal happened in about 1 in 100.

Other studies in different settings have found higher rates, and many prescribers say starting buprenorphine has become harder. So clinicians have adapted. Options include:

• A low-dose start. Very small amounts of buprenorphine are given and built up gradually over several days, so the changeover is gentle.
• Closer monitoring. Some clinicians keep a closer watch on the first day, and researchers are studying other ways to start.
• Methadone. Methadone does not cause precipitated withdrawal and can be started without waiting. It is provided through opioid treatment programs.
• Comfort medicines. Lofexidine or clonidine and other medicines can ease symptoms during the changeover.

These are prescriber decisions. Please do not try to copy a low-dose schedule from the internet. The plan depends on your health and on how the first doses go.

More on each medicine is on the buprenorphine and methadone pages.

Two things make going it alone especially risky with fentanyl.

First, withdrawal is hard enough that many people return to use within days. Second, tolerance drops during that time, and fentanyl is so strong that a small misjudgment can stop your breathing.

Keep naloxone close. NIDA says standard naloxone still reverses most fentanyl overdoses, though some people need a second dose. Call 911 if someone is not breathing or cannot be woken.

When you speak to a prescriber, say that you use fentanyl, or that you think your supply contains it. That one sentence changes the plan. The treatment directory lists providers by state, and our fentanyl guide explains the drug itself.

For a crisis or thoughts of suicide, call or text 988. SAMHSA’s National Helpline, 1-800-662-4357, gives free referrals day and night.