Choosing Methadone Over Morphine

Methadone—isn’t that the drug for heroin addicts?

That’s a question I’m accustomed to hearing from leery patients and families when I inform them that their physician has ordered methadone for pain. While it’s true that methadone is used to treat narcotic withdrawal symptoms, methadone is also a very effective medication to treat moderate to severe pain.

Morphine has earned the title of the gold standard for pain control, the opioid all others are compared to thanks to its effectiveness, ease of administration, and low cost. If morphine is so great, why would we ever use methadone?

If we’re going to start comparing methadone with morphine, we need to start with the basic principles of pain. Pain can be divided into two types of physiological explanations: nociceptive and neuropathic. Nociceptive pain is generally caused by tissue injury (somatic pain) or injury to internal organs (visceral pain). Neuropathic pain is caused by injury or insult to nerves in either the central nervous system or the peripheral body.

We are blessed with opiate receptors in our brains that allow our bodies to respond to opioid pain medications. The majority of these receptors are classified as mu and delta receptors and a smaller percentage are N-methyl D-aspartate (NMDA) receptors. Nociceptive pain is primarily mediated by the mu receptors and neuropathic pain by delta and NMDA receptors; morphine binds to mu receptors only, while methadone binds to mu, delta, and NMDA. Morphine does an excellent job of treating many types of pain, but because of its ability to bind to 100% of opiate receptors, methadone may do it even better.

Opiate Toxicity and Side Effects

Opiates, such as morphine, produce metabolites when they are broken down within the body. These metabolites can build up in the body and cause symptoms of opiate toxicity. Opiate toxicity is essentially an overdose of an opiate leading to poisonous levels in the body and causes symptoms such as restlessness, hallucinations, tremors, and lethargy.​​

Dose-associated deaths due to methadone have been reported in patients due to respiratory depression, although not as commonly as with other opioids.

Common side effects of opiates include constipation, nausea and vomiting, drowsiness, itching, confusion, and respiratory depression (difficulty breathing). Many patients have reported a decrease in adverse effects after switching to methadone from another opiate.

Benefits of Methadone

Methadone is more effective than morphine at treating pain and typically causes fewer adverse effects; another benefit of methadone is its extended half-life. A half-life is the amount of time required for half the quantity of a drug to be metabolized or eliminated by normal biological processes. Because of this extended half-life, methadone has a pain-relieving effect of 8 to 10 hours, while regular non-extended release morphine only relieves pain for two to four hours. This translates into less frequent dosing for the patient, usually two or three times a day.

Also, methadone is extremely cost-effective. A typical month's supply of methadone costs about $8, while morphine will typically cost over $100. Other opiates, such as Oxycontin and Fentanyl, will cost even more.

Barriers to Methadone Use

You may find yourself wondering why methadone is not used more often.

Methadone prescription is restricted in the United States to professionals who have undergone a training program and are licensed to dispense it.

Because of methadone’s extended half-life, it slowly builds up in the body and may take five to seven days for levels to stabilize. During this time, the patient needs to be monitored closely for signs of toxicity. This is generally not a problem for patients on palliative or hospice care, because they are already being followed closely and usually have access to nurses and physicians 24 hours a day. A typical doctor's office does not have the training or capacity to monitor patients that closely. It is usually limited to licensed opioid treatment programs or licensed inpatient units.

Other barriers are physician education and patients' reluctance. Methadone is still widely known as a drug for drug addicts. That stigma is slowly being chipped away as physicians continue to educate their peers on its benefits and the public sees more and more patients finding relief because of it.