The Hospice Clinician Blog

A group of investigators from a Japanese palliative care unit published an article describing the benefits of Baclofen (Lioresal) for managing cancer pain. ⁽¹⁾ This is significant since Baclofen, an effective muscle relaxant, has not previously been studied for its effect as an adjuvant medication specifically for managing cancer pain. Baclofen has potent antispasmodic activity making it a logical choice for numerous conditions associated with muscle spasm and pain related to muscle spasm. There are also reports in the medical literature that describe the effectiveness of Baclofen for certain neuropathic pain syndromes such as trigeminal neuralgia as well as post herpetic neuralgia. ⁽²⁾ Baclofen's mechanism for pain relief is thought to be mediated via the GABA receptors in the central nervous system, a mechanism distinctly separate from that of the opioids which are the primary category of drugs used to manage cancer pain in hospice patients. ⁽³⁾ Adding Baclofen to opioid therapy may make sense from the perspective of attacking the pain from two separate mechanisms of action.

This study was limited to 25 cancer patients who had pain resulting from the following conditions: spinal metastasis, pelvic plexus invasion, thoracic wall invasion, neck invasion, bone metastasis, brachial plexus invasion, celiac plexus invasion, and thalamic pain. The maintenance dosage range was 10mg-40mg per day in 2 to 4 divided doses. Pain was rated by the patient on a numerical rating scale (NRS) of 0 to 10. A 50% or greater reduction in pain according to the NRS was reported by 21 of the 25 patients after the addition of Baclofen. Side effects of sleepiness and GI symptoms were minimized by initiating therapy at a low initial dose of 10mg/day and titrating up to 40mg/day with gradual increases every 2 days depending upon response. Weakness is also a common side effect related to the muscle relaxant properties of Baclofen, however, in this study weakness was only noted in 1 patient. Baclofen was continued for a median duration of 114 days in the 21 patients who reported positive effectiveness.

The effectiveness of Baclofen in a few of the cancerous conditions is not too surprising since these conditions were likely to have a significant neuropathic pain component (ex; pelvic plexus invasion or spinal mets). The interesting finding is that it was also effective for other pain types such as bone metastases. This study suggests that Baclofen can be an effective adjuvant analgesic for managing cancer pain in combination with opioid therapy.

References: (1.) Yomiya, Matsuo, Tomiyasu, et al. Amer.J.Hosp&PalliatCare Med. 2009;Vol26, No2, 112-118. (2.) Fromm, et al. Arch Neurol. 1980;37:768-771 (3.) Chen, Pan . Neuroscience. 2006;142:595-606

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