Acamprosate vs naltrexone: How do they compare?

Medically reviewed by Philip Thornton, DipPharm. Last updated on Oct 30, 2024.

Official answer

by Drugs.com

Acamprosate and naltrexone are two different medications that are used in the treatment of alcohol use disorder. They work in different ways to help people who are dependent on alcohol to abstain from drinking it. Naltrexone is also used for the treatment of opioid use disorder.

Acamprosate was thought to be slightly more effective at helping people with alcohol use disorder remain off alcohol, while naltrexone was thought to be slightly more effective at helping reduce heavy drinking and cravings, according to the results of a meta-analysis which used data from 64 trials.

Results from a small study comparing the two drugs, however, indicates that naltrexone was more effective than acamprosate in a number of areas. The study was conducted in 157 men who had recently undergone alcohol detoxification,

The study found there was no difference in the average time to first drink, but naltrexone recipients had a significantly longer time to relapse (five or more drinks in a day) than acamprosate recipients (63 vs 42 days; p = 0.02). Also, more naltrexone recipients had not relapsed after one year compared with acamprosate recipients (41% vs 17%; p = 0.0009). The number of days participants remained sober was also higher in the naltrexone group, while the number of drinks they had at one time and the severity of their cravings was significantly less (p = 0.038). More participants in the acamprosate group than the naltrexone group were started on disulfiram during the study period.

Another study conducted in 160 participants with alcoholism also noted that naltrexone treatment tended to result in longer times to first drink and relapse compared with acamprosate treatment.

Key facts - acamprosate vs naltrexone
	Acamprosate	Naltrexone
Dosage Form	Delayed-release oral tablet	Oral tablet Extended-release intramuscular injection
Generic / brand names	Generic versions only of the delayed-release oral tablet (Campral brand discontinued)	Generic versions only of the oral tablet (Revia and Depade brands discontinued) Brand name only (Vivitrol) of the extended-release intramuscular injection
FDA approval date	2004	1984 (tablet) 2006 (extended-release intramuscular injection)
Administration	Tablets are taken by mouth (orally)	Tablets are taken by mouth (orally) Extended-release intramuscular injection is administered by gluteal injection into the buttocks
Dosing schedule	Delayed-release oral tablet - three times a day	Oral tablet - once daily, or flexible dosing schedules may be used where tablets are taken on weekdays, or every other day or every third day Extended-release intramuscular injection - every 4 weeks or once a month
Indication / usage	Alcohol use disorder - used for the maintenance of abstinence from alcohol in patients with alcohol dependence who are abstinent at treatment initiation Acamprosate should be used as part of a comprehensive management program that includes psychosocial support. Acamprosate is not used to help the symptoms of alcohol withdrawal.	Alcohol use disorder - used to treat alcohol dependence Opioid use disorder - used for the blockade of the effects of exogenously administered opioids You should stop drinking alcohol or using opioids before starting naltrexone.
Drug type	A small molecule analog of gamma-aminobutyric acid (GABA) and taurine	A small molecule opioid antagonist
Mechanism of action	The exact mechanism is unclear, but it’s thought to work by targeting GABA and N-methyl-D-aspartate (NMDA)	Opioid antagonist
Side effects / adverse effects	Common adverse events that occurred in 3% or greater (and greater than the placebo group in controlled clinical trials) of patients include: Accidental injury Asthenia Pain Anorexia Diarrhea Flatulence Nausea Anxiety Depression Dizziness Dry mouth Insomnia Paresthesia Pruritus Sweating	Common adverse events that occur in more than 10% of patients being treated for alcohol use disorder with naltrexone tablets include: Anxiety Sleeplessness Headache Restlessness Nervousness Abdominal pain Nausea Vomiting Joint Muscle pain Feebleness Common adverse events that occurred in more than 10% of patients being treated for opioid addiction with naltrexone tablets include: Difficulty sleeping Anxiety Nervousness Abdominal pain/cramps Nausea and/or vomiting Low energy Joint and muscle pain Headache Common side effects of naltrexone extended-release intramuscular injection include: Nausea. Nausea may happen after your first injection and usually improves within a few days. Nausea is less likely with future injections Sleepiness Headache Dizziness Vomiting Decreased appetite Painful joints Muscle cramps Cold symptoms Trouble sleeping Toothache
Warnings and precautions	Dose reduction is required for patients with moderate renal impairment Monitor patients for depression or suicidal ideation and prompt patients, families, and caregivers to report such symptoms to the health care provider	Vulnerability to opioid overdose - alert patients they may be more sensitive to opioids after treatment with naltrexone. Life-threatening intoxication can occur Precipitated opioid withdrawal can occur if treatment is initiated while on opioids. A minimum 7-10 day Hepatotoxicity - discontinue use if signs of acute hepatitis develop Depression and suicidality Injection site reactions can occur and may be severe and require surgical management Regional analgesia or use of non-opioid analgesics may be needed for emergency pain management in patients treated with a naltrexone extended-release intramuscular injection Eosinophilic pneumonia has been reported in patients treated with naltrexone extended-release intramuscular injection. Watch for progressive shortness of breath and signs of low blood oxygen levels Hypersensitivity reactions including urticaria, angioedema and anaphylaxis have been reported in patients treated with naltrexone extended-release intramuscular injection
Special patients populations	Only use in pregnancy if the potential benefits outweigh the risks Use with caution in people who are breastfeeding Dose reduction required for moderate renal impairment; contraindicated in severe renal impairment	Only use in pregnancy if the potential benefits outweigh the risks Not recommended in breastfeeding people Use with caution in people with renal impairment

Should I take naltrexone in the morning or at night?

The manufacturer does not specify if you should take naltrexone tablets in the morning or at night. Take naltrexone exactly as your doctor orders it. Many patients take their medication in the morning to help affirm their continued treatment success for either opioid use disorder or alcohol use disorder. Taking naltrexone tablets after a meal (for example: breakfast) may help to lessen any stomach side effects such as nausea or pain. Continue reading

Does naltrexone cause weight gain?

Weight gain is not a common side effect with oral naltrexone treatment. When used in combination with bupropion, naltrexone is approved to help promote weight loss. Naltrexone is known to frequently cause stomach side effects like nausea and vomiting, stomach pain or cramping, and loss of appetite which could contribute to weight loss. Weight gain and increased appetite have been reported as a possible side effect, but is not common. Continue reading

How long does naltrexone take to work?

Oral naltrexone is well absorbed and will usually begin working within one hour after a dose. Intramuscular naltrexone is an extended-release formulation and has two peaks, first at 2 hours then again 2 to 3 days later, although its therapeutic effect lasts for one month Continue reading

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