Methadone (methadone hydrochloride) is available as 5 mg, 10 mg, and 40 mg tablets and as an oral solution.

How It Works

Methadone acts upon specific receptors in the brain and spinal cord to decrease the feeling of pain and to reduce the emotional response to pain. The action of methadone is similar to other synthetic (man-made) medications in the morphine category (opioids). Substances that are derived directly from the opium plant (such as heroin, morphine, and codeine) are known as opiates.

Why It Is Used

Methadone is used to control cancer pain or chronic pain not caused by cancer when other opioids, such as morphine, have not been effective.

Methadone also is commonly used to treat addiction to opiates (such as heroin). Taken once a day, methadone eases opiate withdrawal for 24 to 36 hours, decreasing the chance of relapse.

How Well It Works

Methadone effectively controls cancer pain and other chronic pain not cause by cancer. It may be a good option for someone who has not had a good pain response to other opioids, such as morphine.

As a treatment for opiate addiction, methadone reduces the cravings and withdrawal symptoms caused by opiate use by blocking the "high" and preventing the intense euphoric rush of these drugs. This allows people to avoid the physical and psychological highs and lows caused by changing levels of opiates in the blood, decreasing the chance of relapse. In some cases of opiate addiction, methadone treatment may be needed for several years or longer.

Side Effects

Methadone causes many side effects, including:

Drowsiness.

Lightheadedness.

Weakness and fatigue.

Feelings of elation (euphoria).

Dry mouth.

Difficulty urinating.

Difficulty breathing.

Constipation, which may be severe.

Talk with your health professional about laxative use to prevent constipation.

You can prevent constipation at home. Make sure you drink enough fluids. Most adults should drink between 8 and 10 glasses of water, noncaffeinated beverages, or fruit juice each day. Include fruits, vegetables, and fiber in your diet each day.

Skin reactions, such as irritation, itching, or hives.

What To Think About

Methadone is a long-acting medication and each dose stays in the body for a long time. For this reason dosages should be adjusted with caution, ideally by a pain specialist. It may take a couple of days after the medication is started before the dose of methadone is fully effective.

In some people methadone impairs balance, coordination, or the ability to think. Do not drive or operate any type of equipment if your are taking methadone.

Do not drink alcohol or use other drugs while you are taking methadone.

Methadone can interact with many other medications. Make sure that your health professional is aware of all of the medications that you are taking.

Methadone should be used during pregnancy only if the benefits to the mother outweigh the risks to the fetus. Talk with your health professional before using methadone if you are or may be pregnant. This medication can pass through your body in breast milk and should be avoided while you are nursing.

Methadone was originally developed as a substitute for morphine to relieve pain. Its effectiveness and long duration of action led to its use in maintenance programs for the treatment of heroin addiction. For this reason many people are reluctant to use methadone for cancer pain even though it is very effective.