A once-a-month injection for opioid addiction is more convenient, but it’s not the best option for everyone.

Withdrawal is only a first step toward recovery for someone addicted to opioids.

Once the worst of the withdrawal symptoms are over, people still need to stay drug-free.

This is where maintenance treatments, such as methadone and buprenorphine, come in.

These once-a-day medications — known as opioid agonists — activate the same receptors in the brain as heroin, oxycodone, and other opioids do.

When administered correctly, they reduce cravings for, and the use of, other opioids.

But a new study shows that a medication that blocks the opioid receptors — known as an opioid antagonist — may be just as effective for ongoing addiction treatment.

And it only requires a monthly injection.

In the first head-to-head comparison of an opioid agonist and antagonist, Norwegian researchers randomly assigned 159 people addicted to opioids to drug counseling, and one of two maintenance treatments.

One group received daily pills of buprenorphine-naloxone (Suboxone). The other group received injections of extended-release naltrexone (Vivitrol).

After 12 weeks, the majority of people receiving either medication hadn’t used heroin or other illegal opioids during the previous month.

So in terms of helping people avoid relapsing during those three months, treatment with extended-release naltrexone was similar — or “noninferior,” as the researchers wrote — to buprenorphine-naloxone.

The study was published online last month in JAMA Psychiatry.

Researchers also found that people taking extended-release naltrexone were more satisfied with their treatment, compared to those on buprenorphine-naloxone.

The researchers wrote that this may be due to people on extended-release naltrexone feeling like they’re better protected against relapse and overdose.

Because naltrexone blocks the opioid receptors, it keeps other opioids from binding there. This tamps down on the euphoria, or “high,” that people get when they use opioids.

This makes drug use less rewarding. But it also reduces a person’s risk of overdosing if they’re tempted to use opioids.

“One of the biggest risk factors for people when they detox is that in the 30 days after, they are no longer physically dependent on opiates. They have a very high risk of relapsing to opiates,” Kelly Dunn, PhD, an associate professor of psychiatry and behavioral sciences at Johns Hopkins Medicine, told Healthline.

If they do relapse, they’re at a high risk of overdosing because their body can no longer tolerate the dose that they were accustomed to before withdrawal.

If they can’t get high, they may be less likely to keep using.

A monthly injection may also make it easier for people to stick with their medication.

“If you just have to take a shot once a month, compliance goes up significantly. That’s true in every area of medicine,” Dr. Joseph Garbely, chief medical officer at Caron Treatment Centers, told Healthline.

This may be why some drug courts favor the use of extended-release naltrexone for people whose crimes stem from an opioid addiction.

“The reason many drug courts picked Vivitrol is that they can manage people much easier,” said Garbely. “Basically, if someone doesn’t show up for their next monthly shot, then they’re out of compliance with drug court.”

Vivitrol’s manufacturer, Alkermes, has been criticized for marketing directly to drug court judges.

“I certainly don’t think that it’s appropriate for Alkermes to lobby or advocate like that. That was particularly negative press when this came out,” said Dunn. “It was unfortunate, because I think it could give people a negative impression about the medication.”

Like other medications, though, extended-release naltrexone isn’t without its downsides.

One of these is sudden withdrawal symptoms if a person taking naltrexone is still physically addicted to opioids.

“In order to be transitioned onto naltrexone,” said Dunn, “you have to go through a detox, and show evidence of no physical dependence on opiates.”

This detox, or supervised withdrawal, can be done in different ways. It can include using lower and lower doses of buprenorphine-naloxone, or using medications like ibuprofen to reduce withdrawal symptoms.

The need for a strict detox before starting naltrexone, though, means that this medication may not work for everyone.

“One of the primary reasons that patients continue to use opiates despite negative consequences is because they can’t tolerate the cravings and the withdrawal,” said Dunn.

For them, methadone or buprenorphine can help them get the cravings under control so they can move forward.

“Over time, these people can use counseling services and other things that are provided to them to get their life in order,” said Dunn. “Then they can decide to taper down if they want to.”

Some people on methadone may choose not to taper because of withdrawal or fear of relapsing.

For them, methadone may be the best option.

“They come in early, they get their dose, they go to work and nobody really knows that they’re maintained on methadone,” said Dunn. “They’re fully functional members of the community.”

Other people don’t want to be physically dependent on opioids, so they’re willing to detox. For them, the safety net of naltrexone can be reassuring.

Everyone is different. That’s why having options for treating opioid addiction is important.

“We need choices in medicine,” said Garbely. “Not everyone can take Vivitrol. Not everyone can take Suboxone maintenance. So we have to figure out what is the right medication for the patient.”

These drugs also don’t work in isolation.

“It’s medication-assisted treatment (MAT) — that ‘a’ is not silent,” said Garbely. “The medication just gets the cravings to quiet down, the relapse risks to go away — not entirely, but to go down.”

People being maintained on any of these drugs may also go to counseling, receive psychiatric care for other mental illnesses, or enroll in a 12-step program.

“All these things together, in addition to the medication, gives someone the best chance of progressive recovery,” said Garbely, “and sustaining that recovery.”