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Morphine-like drugs ease nervous system pain

http://www.reutershealth.com/archive/2003/03/26/eline/links/20030326elin003.html

2003-03-26 17:00:17 -0400
By Alison McCook
Reuters Health
New York

Despite concerns about the risk of addiction and side effects from morphine and similar drugs, researchers said Wednesday that this type of medication does, in fact, relieve chronic pain caused by nervous system damage.

Among a group of patients with this type of pain, known as neuropathic pain, eight weeks of treatment with high doses of a drug known as an opioid reduced pain by 36 percent.

In contrast, low doses of the same medication achieved only a 21 percent reduction in reported pain levels. However, people taking the lower dose were less likely to stop taking medication altogether due to side effects.

Examples of opioids include morphine, methadone, OxyContin and codeine.

All of the patients included in the current study had tried other pain medications, but with little success.

Neuropathic pain, and the nerve damage that produces it, stems from a variety of causes, including trauma, stroke or multiple sclerosis.

Neuropathic pain can be especially difficult to treat. However, some experts have raised concerns about using opioids to alleviate patients' pain, study author Dr. Michael C. Rowbotham told Reuters Health.

Opioids can be addictive, he said, and in some patients, the effects of the drug can wane over time, a process known as tolerance.

Furthermore, some researchers have suggested that this type of pain medication simply does not work well in patients with neuropathic pain.

However, based on the current findings, Rowbotham said he would offer opioids to his patients with neuropathic pain, but he recommended that doctors proceed with caution, and tailor treatment with opioids to each individual patient.

"For neuropathic pain, most physicians and patients prefer to give non-opioid treatments a thorough chance before going on to try opioids," Rowbotham said.

"When trying opioids, I recommend that the physician and patient have a clear game plan for how long the opioid will be used, at what dose range, and for how long before making a decision as to whether or not it will become part of their longer term treatment program," he added.

During the current study, published in The New England Journal of Medicine, Rowbotham and his colleagues offered 81 patients either a high dose (0.75 milligrams) form of the opioid levorphanol or a low dose (0.15 milligram) form of the same medication.

Patients were limited to a maximum of 21 pills each day, regardless of dosage.

After eight weeks of treatment, the authors found that patients taking a low dose of the drug tended to pop close to the maximum number of pills every day, while those taking the high-dose form averaged less than 12 capsules daily.

However, patients given the high dose form of levorphanol reported a 36 percent decrease in pain; in contrast, people taking the lower dose of the drug said their pain dropped by only 21 percent.

Twelve patients taking a high dose of levorphanol had to stop taking the drug due to side effects, compared to only three of the patients in the low-dose group. Patients in both the high and low dose groups reported increases in particular side effects - such as drowsiness, muddled thinking, and itchy skin -- during treatment.

Only patients taking a high dose of the treatment, however, reported side effects involving anger, irritability, or personality change.

"The most distressing effects are changes in how the person feels, and this is more common with higher doses," Rowbothan said.

Patients whose neuropathic pain stemmed from stroke were least likely to report a decrease in pain from the drugs, the authors note.

In an accompanying editorial, Dr. Kathleen M. Foley of the Memorial Sloan-Kettering Cancer Center in New York writes that the current study challenges "the traditional view that neuropathic pain is opioid-resistant."

However, the report does not show whether levorphanol and other opioids can ease neuropathic pain in the long-term, she adds. Further research is needed to investigate whether long-term use of these drugs increases the risk of side effects or tolerance to the medication, and whether patients who rotate between different drugs feel better than those who stick with one opioid only.

SOURCE: The New England Journal of Medicine 2003;348:1223-1232,1279-1281.
 

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