Japanese researchers report pain studies
Low-dose intrathecal injections of betamethasone can provide safe, effective, and long-lasting relief of intractable pelvic cancer pain, and low doses of ketamine can provide effective relief for neuropathic cancer pain without the side effects usually associated with the drug, Japanese researchers report in two separate studies.
Their findings were presented at the Interna-tional Symposium: Satellite of 9th Congress of the Pain Clinic, held recently in Tokyo.
"Steroids are administered systematically in patients with advanced cancer to treat pain. Steroids are known to prevent prostaglandin induction in the spinal cord; we studied [whether] intrathecal injection of low-dose betamethasone inhibits severe cancer pain," said H. Matsumoto of Kansai Medical University in Osaka, Japan, in his report.
Matsumoto and colleagues studied three patients with intractable pain caused by perineal or pelvic cancer, administering betamethasone via intrathecal injection through the L4-L5 interlaminal space.
Two of the patients rated their pain as a four or less on a 1-10 scale for one week following injection, the researchers report. The remaining patient’s first injection failed to provide relief. Following a supplemental injection, the patient experienced substantial pain relief for one month. None of the patients reported any negative side effects, according to the report, and all reported a satisfactory improvement in their quality of life.
Low doses of ketamine were found useful in alleviating intractable cancer pain and neuropathic pain, although researchers have yet to determine a preferable route to administer the drug.
"Ketamine, an NMDA receptor antagonist, has recently been used to alleviate intractable pain. However, its optimal dose or the preferable route for its administration has yet to be well established," said S. Takada of Teikyo University in Japan, in a study that was also presented at the International Symposium.
Takada and other researchers studied 13 patients suffering from severe pain refractory to morphine or nonsteroidal anti-inflammatory drugs, treating them with 20 mg to 100 mg ketamine daily, administered epidurally, subcutaneously, or both.
Nine of the 13 patients reported substantial alleviation of painful symptoms following ketamine administration, the researchers said. However, while eight of nine instances of neuropathic pain were responsive to ketamine, only two of nine cases of nociceptive pain were alleviated.
No difference was observed between ketamine administered epidurally or subcutaneously, according to the report. The researchers noted that only one instance of ketamine-related side effects was observed.
"A small dose (<100 mg/day) of ketamine could effectively attenuate neuropathic, but not nociceptive, cancer pain with minimal side effects," Takada concludes in his report. "In view of previous reports showing neurotoxicity of spinally administered ketamine, the subcutaneous route seems more preferable."
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