Naltrexone vs naloxone: the 30-second answer
They sound alike and both block opioid receptors, but they do opposite jobs on opposite timelines. Naloxone (Narcan) is the emergency rescue drug: sprayed or injected during an overdose, it works in minutes and wears off within about an hour or two. Naltrexone is the maintenance medication: taken daily as a pill or monthly as the Vivitrol shot, it blunts craving and blocks opioid effects for weeks at a time. One saves a life mid-overdose; the other protects recovery day after day. No, naltrexone is not the same as Narcan.
Is naloxone the same as naltrexone?
No. The confusion is understandable — both are opioid antagonists built to occupy mu-opioid receptors so opioids cannot activate them. The difference between naloxone and naltrexone is speed and duration by design: naloxone floods receptors almost instantly and clears fast, exactly what an overdose reversal requires; naltrexone binds durably with a long half-life, exactly what relapse prevention requires. They are separate prescriptions for separate moments in recovery.
Mechanism of action, side by side
Pharmacologically the naltrexone vs naloxone mechanism of action is the same class — competitive mu-opioid receptor antagonism — with different pharmacokinetics. Naloxone: onset in 2–3 minutes intranasally, duration roughly 30–90 minutes, negligible oral bioavailability (which is why it works as an abuse deterrent inside Suboxone). Naltrexone: oral 50 mg daily or 380 mg extended-release injection monthly, receptor blockade sustained for weeks, plus documented craving reduction in both opioid and alcohol use disorder, per NIDA and MedlinePlus.
When naloxone is the right tool
During a suspected opioid overdose — slowed or stopped breathing, unresponsiveness, pinpoint pupils. Give naloxone immediately, call 911, and stay until help arrives; a second dose may be needed for fentanyl. Anyone can carry it: naloxone is available at U.S. pharmacies without a personal prescription in nearly every state, and every household touched by opioid use should keep it within reach. Naloxone has no potential for misuse and does nothing in a person without opioids in their system.
When naltrexone is the right tool
After detox, as ongoing protection. For opioid use disorder, naltrexone requires 7–10 opioid-free days first (starting too early triggers precipitated withdrawal), then blocks the effects of any relapse use — the monthly Vivitrol shot removes the daily-pill adherence problem. For alcohol use disorder, naltrexone reduces heavy-drinking days and craving with no opioid-free window needed. It is one of three FDA-approved AUD medications alongside acamprosate and disulfiram.
Naltrexone vs naloxone vs Narcan vs Suboxone
Untangling the three-way searches: Narcan is simply the best-known brand of naloxone nasal spray — same molecule. Suboxone is different territory: it combines buprenorphine (a partial opioid agonist that treats withdrawal and craving) with naloxone as a tamper deterrent — see Vivitrol vs Suboxone. And versus methadone: methadone and buprenorphine activate receptors under control, while naltrexone blocks them outright — three different strategies within medication-assisted treatment, chosen by history, preference, and access.
Can you get both? Cost and access
Often you should. A person on naltrexone maintenance should still keep naloxone at home — blockade fades if doses lapse, and tolerance after abstinence makes relapse overdoses deadlier. Naloxone nasal spray is now over the counter (around $45 retail, frequently free through community programs and health departments); naltrexone is covered by Medicaid, Medicare, and most private plans — oral generics run modest cash prices, Vivitrol bills around $1,000–1,500 per injection and is usually covered as a medical benefit.
Sources
NIDA: Naloxone DrugFacts · MedlinePlus: Naltrexone · SAMHSA: Naltrexone · SAMHSA: Naloxone · FDA: Naloxone information · NIDA: Principles of Effective Treatment