What is the Difference Between Naloxone and Naltrexone

Naloxone and Naltrexone are two types of opioid antagonists. Opioid antagonists are medications that block the effects of opioids. They work by attaching the opioid receptors in the brain, preventing opioids from binding and producing their effects. 

What is the difference between Naloxone and Naltrexone? Naloxone is mainly used as an emergency medication to rapidly reverse the effects of an opioid overdose, whereas Naltrexone is used as a management option for long-term opioid and alcohol addiction.

Key Areas Covered

1. What is Naloxone 
      – Definition, Use
2. What is Naltrexone
      – Definition, Use
3. Similarities Between Naloxone and Naltrexone
      – Outline of Common Features
4. Difference Between Naloxone and Naltrexone
      – Comparison of Key Differences
5. FAQ: Naloxone and Naltrexone
      – Answers to Frequently Asked Questions

Key Terms

Naloxone, Naltrexone, Opioid Antagonists 

What is Naloxone

Naloxone is a rapid-acting medication to reverse the effects of an opioid overdose. The mechanism of action of Naloxone involves binding to opioid receptors in the brain and displacing opioids, which blocks the opioid effects. Due to its rapid action, this medication is used as an emergency medication that promptly corrects critical clinical conditions. This restores normal breathing and consciousness in patients who experience an overdose.

Naloxone is administered to people showing signs of an opioid overdose, such as slowed or stopped breathing, very small or pinpoint pupils, slow heartbeats, and extreme drowsiness or unresponsiveness. It is administered as a nasal spray or injected through intramuscular, subconscious, or intravenous routes. The effects of Naloxone are usually apparent within minutes, but the medication works for only 30 to 90 minutes. Therefore, multiple doses may be necessary, according to the opioid type.

Figure 1: Naloxone Kit

However, administration of Naloxone may cause sudden withdrawal symptoms in opioid-dependent individuals, including nausea, vomiting, diarrhea, stomach pain, fever, sweating, body aches, weakness, tremors, shivering, fast heart rate, and pounding heartbeats.

What is Naltrexone

Naltrexone is a medication that acts as a management option for opioid and alcohol addiction. It is not used as an emergency medication for overdose situations. Naltrexone acts by blocking the euphoric and sedative effects of opioids and alcohol.

Figure 2: Structure of Naltrexone

Naltrexone can also help people with alcohol dependence maintain abstinence by reducing the craving for alcohol, as it blocks the effects of narcotics. It is available in oral tablet form and as an injection, which is an extended-release type. Moreover, its dosage depends on the medical condition of the patient and response to treatment. Naltrexone is generally a part of a comprehensive treatment program, which includes counseling and support. Furthermore, common side effects of this medication include nausea, dizziness, headache, anxiety, and fatigue.

Similarities Between Naloxone and Naltrexone

1. Both Naloxone and Naltrexone medications are opioid antagonists.
2. These medications block the effects of opioids by binding to opioid receptors.
3. Both Naloxone and Naltrexone play roles in treating opioid addiction in different contexts.

Differences Between Naloxone and Naltrexone

Definition 

• Naloxone is an emergency medication for the reversal of opioid overdose, acting rapidly to restore normal respiratory function and consciousness in critical conditions. Naltrexone, on the other hand, is a medication used for long-term management of opioid and alcohol addiction. 

Duration of Action

• Naloxone is short-acting, with effects lasting 30 to 90 minutes, requiring immediate medical follow-up, whereas Naltrexone is long-acting, with sustained effects that support ongoing abstinence from opioids and alcohol.

Route of Administration

• Naloxone can be administered as a nasal spray or injections (intravenous, intramuscular, subconscious), whereas Naltrexone is administered as an oral tablet or extended-release injectable.  

Side Effects

• Naloxone may cause immediate withdrawal symptoms in opioid-dependent individuals, which can be severe, whereas Naltrexone generally causes milder side effects but requires individuals to be opioid-free before starting treatment to avoid precipitated withdrawal.

Conclusion

Naloxone and Naltrexone are two types of opioid antagonists. The main difference between Naloxone and Naltrexone is that Naloxone is mainly used as an emergency medication to rapidly reverse the effects of an opioid overdose, whereas Naltrexone is used as a management option for long-term opioid and alcohol addiction.

FAQ: Naloxone and Naltrexone

1. What is Naloxone used for?

Naloxone is a medication used to rapidly reverse opioid overdoses. It blocks the effects of opioids on the brain, restoring breathing and preventing death.

2. Is Naloxone an antidote?

Yes, Naloxone is an antidote. Specifically, it’s an opioid antagonist that helps to rapidly reverse the effects of opioid overdoses. It blocks opioid receptors in the brain, restoring breathing and consciousness.

3. What is Naltrexone used for?

Naltrexone is a medication used to treat opioid and alcohol addiction. It blocks the effects of these substances, reducing cravings and preventing relapse. Furthermore, it’s often combined with therapy for optimal results.

4. What does Naltrexone do to the brain?

Naltrexone blocks opioid receptors in the brain. This prevents opioids, including alcohol, from producing pleasurable effects. It also reduces cravings by interfering with the brain’s reward system.

Reference: 

1. “Naltrexone HCL – Uses, Side Effects, and More.”  WebMD.
2. “Naloxone.” Drugs.com. 

Image Courtesy:

1. “NaloxoneKit” By James Heilman, MD – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Naltrexone skeletal” By Fvasconcellos (talk · contribs) – Own work using: ACD/ChemSketch 10.0, Inkscape and vim (Public Domain) via Commons Wikimedia