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Opiate-Blocking Drugs: What They Are & How They Work

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Last Updated - 06/19/2024

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Key Takeaways

  • Most drugs that block opioids work by binding to opioid receptors, thereby preventing opioids from binding to the receptors. 
  • Drugs that block opiates can be useful for treating ongoing substance use disorders, addressing some of the side effects of opioids, and for the emergency treatment of opioid overdoses. 
  • There are a variety of different opioid-blocking drugs available, though the majority are only available by prescription. 
  • Opiate blockers have well-documented efficacy but also carry potential side effects and contraindications.
  • Research into opiate blockers is ongoing, focusing on novel medications and personalized treatment approaches.

What Are Opiate Blockers?

Opiate blockers, also known as opioid antagonists, are medications that bind to opioid receptors in the brain. 

Normally, when opioids are ingested, they bond to these opioid receptors. Once bonded, they trigger any of several effects, including euphoria, pain relief, and respiratory depression. 

However, while opiate blockers bind to these receptors, they do not activate them or elicit the effects that opioids do. But by occupying these receptors, opiate blockers prevent opioids from producing their typical effects.  

How Are Drugs That Block Opiates Helpful?

Opiate-blocking drugs provide a number of potential benefits, and they can not only help save lives but also serve as important tools in the pathway to recovery for individuals with substance abuse disorders. 

A few of the key benefits opiate-blockers provide include:

  • They can help reverse opioid overdoses. Opioid blockers like naloxone (Narcan) can be used in emergency situations to rapidly reverse the life-threatening effects of opioid overdose, such as respiratory depression and loss of consciousness. By displacing opioids from their receptors, some of these medications quickly restore normal respiration in individuals experiencing an overdose.
  • They can provide support for individuals suffering from opioid dependence. Medications such as naltrexone (Vivitrol, Revia) are used to help individuals who are recovering from opioid addiction by blocking the euphoric and rewarding effects of opioids. This reduces the incentive to use opioids and helps maintain sobriety.
  • They can address some of the side-effects opioids cause. There are a few medications available that help to address the constipation opioids often trigger. Most of these do not block the pain-relieving effects of opioids, as they specifically target opioid receptors found in the gastrointestinal tract. 
  • They can prevent misuse of opioid medications. In formulations of certain pain medications, opioid blockers can be included to deter abuse. If the medication is taken as prescribed, the opioid blocker has no effect. However, if the medication is tampered with (e.g., crushed and injected), the opioid blocker can prevent the euphoric effects, reducing the potential for abuse.

Are There Risks Associated with Opiate-Blocking Drugs?

While opiate blockers (opioid antagonists) are essential tools in managing opioid overdoses and supporting recovery from addiction, they also come with certain risks and considerations. 

Here are some of the potential risks associated with opiate blockers:

  • Withdrawal Symptoms: Individuals who are physically dependent on opioids can experience sudden and severe withdrawal symptoms.
  • Reduced Pain Relief: For individuals who require opioids for pain management, such as those with chronic pain or undergoing surgery, the use of opioid blockers can interfere with the effectiveness of pain-relief medications.
  • Risk of Overdose After Treatment: After a period of abstinence or treatment with opioid blockers, an individual’s tolerance to opioids decreases. If they relapse and use the same dose of opioids they previously used, there is a higher risk of overdose because their body can no longer handle the same amount.

Common Drugs That Block Opiates

There are a variety of drugs that block opiates available, though they are used in different ways and for different purposes. A few of the most common opiate blocking drugs include:

  • Naloxone (Narcan, Evzio): Used to reverse opioid overdoses, Naloxone can be injected or administered as a nasal spray. It rapidly displaces opioids from their receptors, reversing life-threatening effects like respiratory depression and sedation. It acts quickly, often within minutes, making it essential in emergency overdose situations.
  • Naltrexone (Vivitrol, Revia): Naltrexone is used for the long-term treatment of opioid and alcohol dependence. It is available as an oral tablet (Revia) and a monthly injectable (Vivitrol). Naltrexone blocks the euphoric and sedative effects of opioids, reducing the risk of relapse in individuals who have stopped using opioids. It also helps in managing alcohol dependence by reducing cravings and effects of alcohol.
  • Methylnaltrexone (Relistor): Methylnaltrexone is a bit different from some other drugs that block opiates; it is used to treat opioid-induced constipation. It is available as an injectable or oral tablet, and it works by specifically targeting opioid receptors in the gastrointestinal tract without affecting pain relief provided by opioids.
  • Naloxegol (Movantik): This is another medication used to treat opioid-induced constipation. It is available as an oral tablet, and it largely works the same way methylnaltrexone does. It targets opioid receptors in the gut to relieve constipation without crossing the blood-brain barrier, thus not interfering with central pain relief.
  • Alvimopan (Entereg): Alvimopan is used to accelerate the recovery of bowel function following bowel resection surgery. Available as an oral capsule, this medication acts as a peripheral opioid receptor antagonist to counteract the effects of opioids on the gastrointestinal tract without affecting pain relief.

There are two other drugs that warrant discussion. These medications are not always considered opiate-blocking drugs, but they are often used in the treatment of substance abuse disorders. 

  • Methadone (Dolophine, Methadose): When used for Opioid Use Disorder (OUD), methadone reduces withdrawal symptoms and drug cravings without causing the “high” associated with addiction. It is available as a tablet and liquid.  
  • Buprenorphine (Sublocade, Butrans, Subutex): An opioid medication, buprenorphine is used to treat opioid use disorder (OUD), acute pain, and chronic pain. Unlike other opioids, it reduces cravings and withdrawal symptoms without causing euphoria or dangerous side effects. Buprenorphine acts as a substitute for the drug being abused, allowing patients to focus on recovery. It is available as sublingual tablets, skin patches, and injections.

Understanding the different types of opiate blockers and their mechanisms is crucial for healthcare professionals, as well as patients suffering from opioid dependence and their loved ones.   

Are Drugs That Block Opiates Safe?

Opiate blockers are a critical component in the treatment of opioid addiction and overdose prevention. However, it’s important to consider the safety of any potential medication, including opiate blockers.

Opiate blockers can certainly cause adverse effects such as constipation, nausea, vomiting, and drowsiness. But the benefits of these drugs are often judged to be sufficient to outweigh these relatively minor risks. 

However, more serious side effects are also possible. For example, the primary side effect of opiate blockers is precipitated opioid withdrawal. This can manifest as symptoms including runny nose, watery eyes, yawning, hyperventilation, and hyperthermia.  

Additionally, when opiate blockers are administered in emergencies, they can rapidly reverse the effects of opioids, leading to immediate withdrawal symptoms. This abrupt onset of withdrawal can be both uncomfortable and dangerous for the individual.

Accordingly, the FDA emphasizes the importance of prescribing these drugs appropriately, and only after weighing all the important factors, such as any other medications the patient is taking. The FDA also cautions physicians to be aware of the risks of undertreatment, which can lead to illicit substance use for self-treatment.  

Ultimately, appropriate safety protocols, including regular reassessments and education on the risks and goals of therapy, are crucial for mitigating the risks associated with opiate blockers.  

The Future of Opioid-Blocking Drugs

While opioid-blocking drugs have proven very helpful in addressing opioid dependency, there still exists significant room for improvement. For example, concerns have been raised about their efficacy against highly potent synthetic opioids like fentanyl. 

This, as well as the general desire to increase the number of treatment options available, has led researchers to investigate other potential medications. One such experimental drug, VX-548, has shown promise in clinical trials for treating moderate-to-severe acute pain without the same safety risks associated with opioids. 

Unlike opioids, which act on the brain, VX-548 targets pain at its source in the peripheral nervous system, potentially sidestepping the addictive properties and other negative side effects of opioids.

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