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Methadone injection may be habit forming. Use methadone injection exactly as directed. Do not use more or less of it, stop using it suddenly, use it more often, or use it for a longer period of time or in a different way than prescribed by your doctor. Tell your doctor if you or anyone in your family drinks or has ever drunk large amounts of alcohol, uses or has ever used street drugs, or has overused prescription medications, or has had an overdose, or if you have or have ever had depression or another mental illness.
Methadone injection may cause serious or life-threatening breathing problems, especially during the first 24 to 72 hours of your treatment and any time your dose is increased. If you experience any of the following symptoms, call your doctor or get emergency medical treatment: slowed breathing, long pauses between breaths, or shortness of breath.
Taking certain other medications, drinking alcohol, or using street drugs during your treatment with methadone injection may increase the risk that you will experience serious, life-threatening side effects such as breathing problems, sedation, or coma. Tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, and nutritional supplements you are taking or plan to take. Your doctor may need to change the doses of your medications and will monitor you carefully.
Methadone injection may harm or cause death to other people who take your medication, especially children. Keep methadone injection in a safe place so that no one else can take it accidentally or on purpose.
Methadone injection may cause QT prolongation (a rare heart problem that may cause irregular heartbeat, fainting, or sudden death). If you experience any of the following symptoms, call your doctor immediately: pounding heartbeat, dizziness, lightheadedness, or fainting.
Tell your doctor if you are pregnant or plan to become pregnant. If you use methadone injection regularly during your pregnancy, your baby may experience life-threatening withdrawal symptoms after birth.
Talk to your doctor about the risks of using methadone injection for your condition.
Use of methadone to treat opiate addiction:
If you have been addicted to an opiate (narcotic drug such as heroin), and you are using methadone injection to help you stop taking or continue not taking the drug, you must enroll in a treatment program. You may have to take your medication at the treatment program facility under the supervision of the program staff. Ask your doctor or the treatment program staff if you have any questions about enrolling in the program or taking or getting your medication.
WHY is this medicine prescribed?
Methadone injection is used to relieve severe pain. Methadone also is used to treat opioid addiction (physical and psychological reliance on a chemical found in prescription and street drugs). Methadone is in a class of medications called opiate (narcotic) analgesics. Methadone works to treat pain by changing the way the brain and nervous system respond to pain. It works to treat people who were addicted to opiate drugs by producing similar effects and preventing withdrawal symptoms.
HOW should this medicine be used?
Methadone injection comes as a solution (liquid) to inject subcutaneously (just under the skin), intramuscularly (into a muscle), or intravenously (into a vein). Inject once every 8 to 12 hours. When methadone injection is used to prevent withdrawal symptoms, it is given by a doctor or nurse in a medical facility.
Your doctor may change your dose of methadone during your treatment. Your doctor may decrease your dose or tell you to use methadone injection less often as your treatment continues. If you experience pain during your treatment, your doctor may increase your dose or may prescribe an additional medication to control your pain. Talk to your doctor about how you are feeling during your treatment with methadone injection. If you feel that your pain is not controlled or if your pain increases, becomes worse, or if you have new pain or an increased sensitivity to pain while you are using methadone injection, call your doctor. Do not use extra doses of methadone injection or use doses of methadone injection earlier than they are scheduled even if you experience pain.
Talk to your doctor or pharmacist about access to rescue medicines, naloxone or nalmefene, while receiving methadone injection. Rescue medications can reverse the life-threatening effects of an opioid overdose and are available over the counter or with a prescription. Make sure that you and your family members and people usually around you know how to recognize an overdose, how to use naloxone or nalmefene, and what to do until emergency medical help arrives. Your doctor or pharmacist will show you and others how to use it. If symptoms of an overdose occur, they should give the first dose of naloxone, call 911 immediately, and stay with you and watch you closely until emergency medical help arrives. If your symptoms return, the person should give you another dose of the rescue medication. Additional doses may be given every 2 to 3 minutes, if symptoms return before medical help arrives.
Do not stop using methadone injection without talking to your doctor. Your doctor will probably want to decrease your dose gradually. If you suddenly stop using methadone, you may experience withdrawal symptoms such as restlessness, teary eyes, runny nose, yawning, sweating, chills, muscle pain, widened pupils (black circles in the middle of the eyes), irritability, anxiety, backache, joint pain, weakness, stomach cramps, difficulty falling asleep or staying asleep, nausea, decreased appetite, vomiting, or diarrhea.
Ask your pharmacist or doctor for a copy of the manufacturer's information for the patient.
Are there OTHER USES for this medication?
This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.
What SPECIAL PRECAUTIONS should I follow?
Before using methadone injection,
What SPECIAL DIETARY instructions should I follow?
Unless your doctor tells you otherwise, continue your normal diet.
What SIDE EFFECTS can this medicine cause?
Methadone may cause side effects. Tell your doctor if any of these symptoms or those in the SPECIAL PRECAUTIONS section are severe or do not go away:
Some side effects can be serious. If you experience any of these symptoms or those listed in the IMPORTANT WARNING section, call your doctor immediately or get emergency medical treatment:
Methadone injection may cause other side effects. Call your doctor if you have any unusual problems while using 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).
What should I do in case of OVERDOSE?
In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at http://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.
Symptoms of overdose may include:
What should I know about STORAGE and DISPOSAL of this medication?
Keep this medication in the container it came in, tightly closed, out of reach of children, and in a location that is not easily accessible by others, including visitors to the home. Store it at room temperature and away from excess heat and moisture (not in the bathroom).
Dispose of any medication that is outdated or no longer needed through a medicine take-back program. If you do not have a take-back program nearby or one that you can access promptly, flush any methadone injection solution that is outdated or no longer needed down the toilet. Talk to your pharmacist about the proper disposal of your medication.
Keep all medication out of sight and reach of children as many containers are not child-resistant. Always lock safety caps. Place the medication in a safe location - one that is up and away and out of their sight and reach. http://www.upandaway.org
What OTHER INFORMATION should I know?
Keep all appointments with your doctor or clinic.
Before having any laboratory test, tell your doctor and the laboratory personnel that you are using methadone injection.
This prescription is not refillable. If you continue to experience pain after you finish using methadone injection, call your doctor. If you take this medication on a regular basis, be sure to schedule appointments with your doctor so that you do not run out of medication.
Keep a written list of all of the prescription and nonprescription (over-the-counter) medicines, vitamins, minerals, and dietary supplements you are taking. Bring this list with you each time you visit a doctor or if you are admitted to the hospital. You should carry the list with you in case of emergencies.
This report on medications is for your information only, and is not considered individual patient advice. Because of the changing nature of drug information, please consult your physician or pharmacist about specific clinical use.
The American Society of Health-System Pharmacists, Inc. represents that the information provided hereunder was formulated with a reasonable standard of care, and in conformity with professional standards in the field. The American Society of Health-System Pharmacists, Inc. makes no representations or warranties, express or implied, including, but not limited to, any implied warranty of merchantability and/or fitness for a particular purpose, with respect to such information and specifically disclaims all such warranties. Users are advised that decisions regarding drug therapy are complex medical decisions requiring the independent, informed decision of an appropriate health care professional, and the information is provided for informational purposes only. The entire monograph for a drug should be reviewed for a thorough understanding of the drug's actions, uses and side effects. The American Society of Health-System Pharmacists, Inc. does not endorse or recommend the use of any drug. The information is not a substitute for medical care.
AHFS® Patient Medication Information™ Copyright, 2025. The American Society of Health-System Pharmacists®, 4500 East-West Highway, Suite 900, Bethesda, Maryland. All Rights Reserved. Duplication for commercial use must be authorized by ASHP.
Selected Revisions: October 15, 2025.