Naltrexone and naloxone are often confused due to their similar-sounding names and shared classification as opioid antagonists. Both medications interact with opioid receptors in the body, but they serve very different purposes in medical practice. Understanding their distinct roles is important for those seeking information about opioid-related treatments and emergency interventions.
Understanding Naloxone
Naloxone is a medication that rapidly reverses the effects of an opioid overdose. As an opioid antagonist, it binds strongly to opioid receptors in the brain, displacing existing opioids. This action quickly restores normal breathing to a person whose respiration has slowed or stopped due to an opioid overdose, typically within 2 to 3 minutes.
Its effects are short-lived, generally lasting between 30 and 90 minutes. Because many opioids remain in the body longer than naloxone, multiple doses may be necessary to prevent re-sedation and allow for continuous monitoring. It is commonly available as a nasal spray (e.g., Narcan or Kloxxado) and as an injectable solution (intramuscularly, intravenously, or subcutaneously).
Understanding Naltrexone
Naltrexone is used in the long-term management of opioid use disorder (OUD) and alcohol use disorder (AUD). It blocks the euphoric and sedative effects of opioids by binding to opioid receptors, particularly the mu-opioid receptor. This blockade helps reduce cravings for both opioids and alcohol, supporting individuals in their recovery.
Unlike naloxone, naltrexone has a longer-lasting effect. It is available as an oral tablet, often taken daily, or as an extended-release injectable form (e.g., Vivitrol), administered once a month. Individuals with OUD must be opioid-free for at least 7 to 10 days before starting naltrexone to avoid precipitating severe withdrawal symptoms. Naltrexone does not cause physical dependence and is not an opioid itself.
Key Distinctions Between Them
The fundamental difference between naloxone and naltrexone lies in their primary purpose and duration of action. Naloxone is an emergency medication for acute opioid overdose reversal, quickly restoring breathing and consciousness. Its rapid, short-lived effects necessitate immediate medical follow-up, as opioids can outlast its duration.
Naltrexone, conversely, is for ongoing treatment of substance use disorders, not an emergency intervention. It prevents the euphoric effects of opioids and reduces cravings over extended periods, taken daily as oral tablets or monthly via injection. While naloxone is given as a single dose in an emergency, naltrexone is part of a sustained regimen to support long-term recovery and prevent relapse. Naloxone can induce immediate opioid withdrawal symptoms upon administration to an opioid-dependent individual.
Applications of Each Medication
Naloxone’s primary application is in emergency situations to reverse an opioid overdose. First responders, healthcare professionals, and trained laypersons use it to counteract life-threatening respiratory depression caused by opioids. Its widespread availability, including as an over-the-counter nasal spray, has made it an important tool in reducing opioid overdose fatalities. It is administered when signs of overdose, such as slowed breathing or unresponsiveness, are observed.
Naltrexone is applied in comprehensive treatment plans for individuals recovering from opioid use disorder and alcohol use disorder. For OUD, it helps maintain abstinence by blocking the effects of consumed opioids, thereby removing the “reward.” In AUD treatment, naltrexone reduces cravings and the pleasurable effects of alcohol, assisting individuals in cutting back or achieving abstinence, especially when combined with counseling and support programs.