Nalmefene injection is used along with emergency medical treatment to reverse the life-threatening effects of a known or suspected opiate (narcotic) overdose. Nalmefene injection is in a class of medications called opiate antagonists. It works by blocking the effects of opiates to relieve dangerous symptoms caused by high levels of opiates in the blood.

Nalmefene injection comes as a solution (liquid) to be injected intravenously (into a vein), intramuscularly (into a muscle), or subcutaneously (just under the skin). It is usually given as needed to treat opiate overdoses.

Nalmefene injection may not reverse the effects of certain opiates such as buprenorphine (Belbuca, Buprenex, Butrans, Sublocade) and pentazocine (Talwin) and additional nalmefene doses may be required.

Before receiving nalmefene injection,

• tell your doctor and pharmacist if you are allergic to nalmefene injection, related drugs, any other medications, or any of the ingredients in nalmefene injection. Ask your pharmacist for a list of the ingredients.
• tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take.
• tell your doctor if you have recently had surgery or if you have or have ever had seizures, or heart, liver, or kidney disease.

In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at https://www.poisonhelp.org/help. If the victim has collapsed, had a seizure, has trouble breathing, or can't be awakened, immediately call emergency services at 911.

Nalmefene injection may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

• nausea
• vomiting
• headache
• fever
• chills
• dizziness
• tiredness

Some side effects can be serious. If you experience any of these symptoms, call your doctor immediately or get emergency medical treatment:

• signs of opiate withdrawal such as body aches; diarrhea; fast, pounding, or irregular heartbeat; fever; runny nose; sneezing; sweating; yawning; nausea; vomiting; nervousness; restlessness; irritability; shivering or trembling; stomach cramps; weakness; and the appearance of hair on the skin standing on end
• seizures

Nalmefene injection may cause other side effects. Call your doctor if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online (http://www.fda.gov/Safety/MedWatch) or by phone (1-800-332-1088).

This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.

Keep all appointments with your doctor.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.