nalmefene

Action and Spectrum

Actions and Spectrum:

nalmefene is an opioid receptor antagonist used primarily for the treatment of alcohol dependence. It is structurally similar to another opioid antagonist called naltrexone but has a longer duration of action.

• Opioid Receptor Antagonist: nalmefene acts as a competitive antagonist at opioid receptors, specifically the mu-opioid receptors, which are involved in mediating the effects of opioids and endorphins. By blocking these receptors, nalmefene inhibits the binding and activation of opioid substances, preventing their analgesic and euphoric effects.
• Alcohol Dependence Treatment: nalmefene is used as a pharmacological treatment for alcohol dependence in adults who have alcohol-related problems but do not require immediate detoxification. It helps reduce alcohol cravings and consumption by interfering with the brain’s reward pathway, reducing the pleasurable effects of alcohol consumption.
• Reduces Alcohol Consumption: nalmefene has been shown to reduce the amount of alcohol consumed and the number of heavy drinking days in individuals with alcohol dependence.
• Long-Lasting Action: nalmefene has a longer half-life compared to naltrexone, meaning it remains active in the body for an extended period, allowing for less frequent dosing. This feature may improve treatment adherence.
• Limited Withdrawal Symptoms: Nalmefene does not produce significant withdrawal symptoms when administered in alcohol-dependent individuals. This is an essential aspect of its use, as it allows for a safer and more manageable treatment process.

Spectrum: The spectrum of nalmefene is primarily related to its actions as an opioid receptor antagonist and its use in the treatment of alcohol dependence. It does not have significant agonistic effects on opioid receptors, meaning it does not produce opioid-like effects itself. Instead, it is used to counteract the effects of opioids and prevent the rewarding properties of alcohol, which can help in reducing alcohol consumption and dependence.

Drug Interaction

Adverse Reaction

Frequency defined

1-10%

Hypertension (5%)

Fever (3%)

Postoperative pain (4%)

Dizziness (3%)

Tachycardia (5%)

Chills (1%)

Headache (1%)

Vomiting (9%)

10%

Nausea (18%)

Black Box Warning

Black Box Warning:

None

Contraindication / Caution

Nalmefene is contraindicated in patients hypersensitive to the formulation’s active ingredient and other excipients. 

Pregnancy / Lactation

Pregnancy consideration:  

The drug should be given during pregnancy only when highly required. 

Breastfeeding warnings:  

Exercise caution while administering the drug during lactation. 

Pregnancy category: 

• Category A: well-controlled and Satisfactory studies show no risk to the fetus in the first or later trimester.        
• Category B: there was no evidence of risk to the fetus in animal studies, and there were not enough studies on pregnant women        
• Category C: there was evidence of risk of adverse effects in animal reproduction studies, and no adequate evidence in human studies must take care of potential risks in pregnant women.       
• Category D: adequate data available with sufficient evidence of human fetal risk from various platforms, but despite the potential risk, and used only in emergency cases for potential benefits.        
• Category X: Drugs listed in this category outweigh the risks over benefits. Hence these categories of drugs need to be avoided by pregnant women.        
• Category N: There is no data available for the drug under this category  

Pharmacology

Pharmacology:

nalmefene is a medication used in the management of alcohol dependence and to reduce alcohol consumption in individuals with alcohol use disorder. It belongs to a class of drugs known as opioid antagonists.

Pharmacology:

nalmefene acts as a competitive antagonist at opioid receptors, primarily targeting the mu-opioid receptors in the brain. By binding to these receptors, nalmefene blocks the effects of endogenous opioid peptides (endorphins and enkephalins) as well as exogenous opioid drugs. The mu-opioid receptors are involved in the brain’s reward system and play a role in the pleasurable effects of alcohol and other substances of abuse.

Pharmacokinetics:

Absorption:

nalmefene is well-absorbed after oral administration, and its peak plasma concentration is typically achieved within 1 to 2 hours.

Distribution:

nalmefene has a moderate volume of distribution, indicating that it distributes relatively well throughout the body tissues.

Protein Binding:

nalmefene binds extensively to plasma proteins, with approximately 45% to 55% of the drug being bound.

Metabolism:

nalmefene is extensively metabolized in the liver by various enzymes, including glucuronidation and N-dealkylation. The primary metabolite is nalmefene 3-glucuronide, which is inactive.

Elimination:

The elimination half-life of nalmefene is relatively long, ranging from 8 to 13 hours. This extended half-life contributes to the drug’s ability to block opioid receptors for an extended period, making it suitable for use in alcohol dependence treatment.

Excretion:

nalmefene and its metabolites are primarily eliminated through the urine, with only a small fraction being excreted in the feces.

Adminstartion

Administration:

The dosage of nalmefene varies depending on the patient’s condition and response to treatment. Typically, it is taken as an oral tablet and prescribed for a specific duration as part of a larger treatment plan.

Patient Information Leaflet

Patient information leaflet 

Generic Name: nalmefene 

Pronounced: nal-mef-ene 

Why do we use nalmefene? 

nalmefene is an opioid receptor antagonist, which means it blocks the effects of opioids by binding to opioid receptors without activating them. It is primarily used for the management of alcohol dependence, but it can also be used in certain cases of opioid overdose.

When a person overdoses on opioids, such as heroin, fentanyl, or prescription opioids, they may experience severe respiratory depression, which can be life-threatening. Opioids act on the central nervous system to depress respiratory drive, leading to slow and shallow breathing or even complete cessation of breathing. This condition is a medical emergency and requires immediate intervention.

nalmefene, being an opioid receptor antagonist, can rapidly reverse the effects of opioids, including respiratory depression. When administered during an opioid overdose, nalmefene competes with the opioid for binding to the receptors, displacing the opioid and blocking its effects. This action can quickly restore normal breathing and reverse the life-threatening consequences of the overdose.