Opioid Blocker Shot: A Monthly Injection to Overcome Addiction


If you, or someone you know, are suffering from opioid addiction, and daily pills aren’t a viable option, a monthly opioid blocker shot might be a better alternative.

These shots can be helpful in treating opioid addiction, especially for patients who may not be able to keep taking pills at fixed times every day. Here’s everything you need to know about naltrexone and buprenorphine monthly opioid blocker shots.

What Is an Opioid Blocker Shot?

An opioid blocker shot is an injection that doctors administer to help patients with Opioid Use Disorder (OUD). Often, this is a monthly intramuscular injection administered in private in a hospital or a clinic.

This allows for privacy if the patient doesn’t want anyone to know that they’re undergoing opioid addiction therapy.

Such an injection is highly convenient because the patient has to schedule it once a month. Compared to oral daily pills, which must be taken every day at specific times, injectable blocker shots are less of a commitment.

Examples of Opioid Blocker Shots

We’ll focus on the two most popular injectable drugs used to block opioid action: Naltrexone (Vivitrol) and Buprenorphine (Suboxone).

The reason why opioids are addictive is because of the feeling of pleasure and pain relief they provide upon usage. This has good medical potential because it helps in severe pain where other medications aren’t effective.

However, prolonged or abused usage can lead to addiction. Not every patient who suffers from OUD is an actual drug addict who intentionally obtained the drug illegally. Many of them are just patients who were prescribed the medication but got used to its effects.

The mechanism of action for both opioid blockers involves “blocking” the addictive opioids from binding to their receptors in the nervous system. They stop the opioids from achieving their effects by preventing them from binding to their receptors, helping the patient to overcome the addiction.

Naltrexone and buprenorphine have a similar mechanism, but they’re used in different stages of the treatment. Here’s how they’re used:


As mentioned earlier, naltrexone binds to opioid receptors in the brain, stopping opioids from achieving their effect.

The unique aspect of naltrexone is that it doesn’t cause addiction. That’s because, despite binding to the opioid receptors, it doesn’t activate them.

In other words, it doesn’t provide any of the good feelings one would get from taking opioids. This discourages the patient from using any opioids during therapy.

This drug is available in both pill and injectable forms.

Naltrexone Side Effects

Naltrexone is a safe drug. It rarely has any severe side effects. Most side effects are mild, and the body often overcomes them during therapy.

Some of the most common side effects include:

  • Loss of appetite
  • Constipation
  • Muscle cramps
  • Random body pains
  • Nausea and vomiting

These side effects can be handled at home by most people as long as they don’t have any allergy to the drug.

Some of the uncommon side effects include:

  • Pain around the liver area under the stomach
  • Dark urine
  • At the injection site: open wounds, blisters, rashes, hard areas, or lumps.

If the patient experiences any of these side effects, they should inform their doctor to evaluate the condition and potentially change the medication.

The injection site side effects, in particular, usually arise from faulty injection and/or allergic reactions. Typically, the doctor should have already ruled out allergic reactions by performing allergy skin tests.

Considerations While Taking Naltrexone

There are a few things the patient should be aware of if they want to undergo naltrexone therapy:

This Drug Assists, But Doesn’t Treat

Naltrexone is a part of Medication Assisted Treatment or MAT. It doesn’t stop the patient from craving opioids, and since it doesn’t activate the receptors, it doesn’t provide any good feelings either. If anything, patients may still crave opioids while taking naltrexone.

The patient should be clearly informed that naltrexone’s primary effect is to make the impact of opioids less desirable, which can help them overcome their opioid dependence. Naltrexone is used along with other medications and counseling to help the patient become opioid-free.

Naltrexone May Indirectly Lead to a Fatal Opioid Overdose

Naltrexone’s therapeutic index is high. If you’re taking the 50 mg pills, you’ll need three pills a day to start overdosing on the drug. This risk is even less with injectable naltrexone since you go to your doctor once a month to get the injection.

There’s no risk of overdose even when accidentally taking the pill twice a day. However, there’s still potential to overdose from taking opioids. If the patient relapses during therapy and starts taking opioids, they’ll likely get nothing from their regular dose.

Since vulnerable moments can lead to impaired judgment, they might resort to doubling up on the opioid, leading to a fatal overdose.

Naltrexone Should Never Be Taken During Withdrawal Symptoms

When the patient stops taking opioids, they’ll start experiencing withdrawal symptoms a couple of days after the last dose. Depending on the patient, type of opioid, and how long it has been taken, these symptoms can last 7-10 days, and sometimes more.

Naltrexone therapy should not begin during that period, as it can elongate that already difficult period even more.

The Patient Has to Provide an Accurate Medical History

Naltrexone may not be dangerous, but it can interact with many drugs, some of which are standard prescription and OTC medications. These drug interactions can lead to unpredictable results, which could be dangerous.


Much like naltrexone, buprenorphine is used to treat opioid addiction. Besides pills and monthly injections, it also comes as a film placed under the tongue.

However, unlike naltrexone, which is used after the withdrawal symptoms have lessened, buprenorphine can be used immediately after the last opioid dose.

The reason behind this is its mechanism of action.

Buprenorphine attaches to the opioid receptors to prevent other opioids from binding to them, just like naltrexone. However, the difference here is that buprenorphine partially activates those receptors.

It produces a feeling of pleasure and relief, but because of its partial activation, the feeling isn’t as strong as with opioids.

This allows the medication to be used as a tool to help the patient through the withdrawal period.

Buprenorphine Side Effects

Buprenorphine has a list of side effects that are pretty close to naltrexone. Here are some of the side effects:

  • Nausea and vomiting
  • Generalized muscle aches
  • Decreased appetite
  • Constipation
  • Sleeplessness or insomnia
  • Fatigue and sweating

Fortunately, most people get used to the side effects quickly, while some others experience none of them. Buprenorphine therapy is generally easier than naltrexone, as it provides a slight relief to the patient.

However, the dose will be gradually reduced until the end of therapy, after which the patient may start naltrexone therapy (or any other opioid blocker).

Considerations While Taking Buprenorphine

Buprenorphine is often safer than naltrexone, but there are a few things to keep in mind.

It Can Be Addictive

Buprenorphine partially activates the opioid receptors it binds to. This partial activation has a far lower risk of addiction than regular opioids.

However, as long as there’s activation, there’s a chance of addiction.

Fortunately, doses are often controlled and monitored, reducing such a risk as much as possible.

It Can Interact With Other Drugs

Any medication that acts on the body’s opioid receptors can interact with other medicines that perform the same function. That’s why the patient needs to let their doctor know if they’re currently taking any opioids for any reason.

Some prescription and OTC drugs can interact with buprenorphine as well. An accurate medical history is paramount.

It Likely Shouldn’t Be Used During Pregnancy or Lactation

Doctors should weigh the risks vs benefits before prescribing injectable buprenorphine to pregnant women due to insufficient studies. It can also pass into the breast milk, which is why it’s not recommended for lactating mothers.

Final Words

Many medications can be used as opioid blocker shots, but naltrexone and buprenorphine are the most common ones.

Both medications are parts of medical-assisted therapies, and they both work on the opioid receptors in the brain.

Buprenorphine can be used during the withdrawal effect period as it provides partial activation of the receptors, which can cause addiction.

Naltrexone, on the other hand, binds to the receptors without activating them, reducing the addiction risk to the minimum. Still, it can’t be used during the withdrawal period, or it will prolong the symptoms.

Both medications should be used under the doctor’s supervision, and the patient should report any side effects.


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