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Discontinued Warning IconPlease Note: This Brand Name drug is no longer available in the US.
(Generic versions may still be available.)

Revex Side Effects Center

Medical Editor: John P. Cunha, DO, FACOEP

Last reviewed on RxList 1/22/2016

Revex (nalmefene hydrochloride injection) is an opioid antagonist used to treat a narcotic overdose or other situation in which opioid side effects may be harmful. The brand name Revex is discontinued, but generic versions may be available. Common side effects of Revex (nalmefene hydrochloride injection) include nausea, vomiting, fast heart rate, stomach pain, muscle or joint pain, chills, fever, dizziness, headache, low blood pressure (hypotension), or feeling anxious or depressed.

The recommended dose of Revex for reversal of postoperative opioid depression is 100 g/mL dosage strength (blue label). For management of known or suspected opioid overdose, use 1.0 mg/mL dosage strength (green label). Revex may interact with other drugs. Tell your doctor all medications and supplements you use. Revex is not expected to be harmful to a fetus. However, opioid medications are not recommended for use during pregnancy. This drug may pass into breast milk and could harm a nursing baby. Consult your doctor before breastfeeding. Withdrawal symptoms may occur if you suddenly stop taking this medication.

Our Revex (nalmefene hydrochloride injection) Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What is Prescribing information?

The FDA package insert formatted in easy-to-find categories for health professionals and clinicians.

Revex FDA Prescribing Information: Side Effects
(Adverse Reactions)


Adverse event information was obtained following administration of REVEX to 152 normal volunteers and in controlled clinical trials to 1127 patients for the treatment of opioid overdose or for postoperative opioid reversal.

Nalmefene was well tolerated and showed no serious toxicity during experimental administration to healthy individuals, even when given at 15 times the highest recommended dose. In a small number of subjects, at doses exceeding the recommended REVEX dose, nalmefene produced symptoms suggestive of reversal of endogenous opioids, such as have been reported for other narcotic antagonist drugs. These symptoms (nausea, chills, myalgia, dysphoria, abdominal cramps, and joint pain) were usually transient and occurred at very low frequency.

Such symptoms of precipitated opioid withdrawal at the recommended clinical doses were seen in both postoperative and overdose patients who were later found to have had histories of covert opioid use. Symptoms of precipitated withdrawal were similar to those seen with other opioid antagonists, were transient following the lower doses used in the postoperative setting, and more prolonged following the administration of the larger doses used in the treatment of overdose.

Tachycardia and nausea following the use of nalmefene in the postoperative setting were reported at the same frequencies as for naloxone at equivalent doses. The risk of both these adverse events was low at doses giving partial opioid reversal and increased with increases in dose. Thus, total doses larger than 1.0 µg/kg in the postoperative setting and 1.5 mg/70 kg in the treatment of overdose are not recommended.

Relative Frequencies of Common Adverse Reactions With an Incidence Greater than 1% (all patients, all clinical settings)

Adverse Event Nalmefene Naloxone Placebo
N=1127 N=369 N=77
Nausea 18% 18% 6%
Vomiting 9% 7% 4%
Tachycardia 5% 8% -
Hypertension 5% 7% -
Postoperative pain 4% 4% N/A
Fever 3% 4% -
Dizziness 3% 4% 1%
Headache 1% 1% 4%
Chills 1% 1% -
Hypotension 1% 1% -
Vasodilatation 1% 1% -

Incidence less than 1%

CARDIOVASCULAR: Bradycardia, arrhythmia

DIGESTIVE: Diarrhea, dry mouth

NERVOUS SYSTEM: Somnolence, depression, agitation, nervousness, tremor, confusion, withdrawal syndrome, myoclonus

RESPIRATORY: Pharyngitis

SKIN: Pruritus

UROGENITAL: Urinary retention

The incidence of adverse events was highest in patients who received more than the recommended dose of REVEX.

Laboratory findings

Transient increases in CPK were reported as adverse events in 0.5% of the postoperative patients studied. These increases were believed to be related to surgery and not believed to be related to the administration of REVEX. Increases in AST were reported as adverse events in 0.3% of the patients receiving either nalmefene or naloxone. The clinical significance of this finding is unknown. No cases of hepatitis or hepatic injury due to either nalmefene or naloxone were observed in the clinical trials.

Drug Abuse And Dependence

REVEX is an opioid antagonist with no agonist activity. It has no demonstrated abuse potential, is not addictive, and is not a controlled substance.

Read the entire FDA prescribing information for Revex (Nalmefene Hydrochloride)

Report Problems to the Food and Drug Administration


You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.

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