Cubero, D.I., & del Giglio, A. (2010). Early switching from morphine to methadone is not improved by acetaminophen in the analgesia of oncologic patients: A prospective, randomized, double-blind, placebo-controlled study. Supportive Care in Cancer, 18, 235–242.doi: 10.1007/s00520-009-0649-8
To evaluate the efficacy of methadone as a substitute for morphine, and to investigate whether the addition of acetaminophen improves pain control in switching to methadone
Patients using morphine for oncologic pain who were on a stable dose for at least one week were recruited. Patients were rapidly switched to oral methadone without a transition period and randomized to receive acetaminophen or placebo with methadone for seven days. The daily morphine dose was converted to methadone in ratios according to the total daily morphine dose. In case of additional pain, patients were instructed to use extra methadone no more than every two hours using a dose equal to 25% of the total daily dose. Use of coanalgesics such as anti-inflammatory drugs, antidepressants, and neuroleptics was allowed. Pain intensity was evaluated daily and recorded by patients in a diary along with all analgesic medications used. Patients were followed for seven days.
The study design was double-blind, randomized, placebo-controlled for use of acetaminophen, and open label for switch to methadone.
Of the original study sample, 16% ended participation early due to treatment failure with intense pain, somnolence, or vomiting. Most patients who completed the study had a significant improvement in pain by the faces (p = 0.05) and numeric (p = 0.03) rating scales. There were no differences between patients who did and did not receive acetaminophen.
Study findings show that most patients can be switched from morphine to methadone with no transition period, with some improvement in side effects of constipation and xerostomia and adequate pain control. The addition of acetaminophen in this process was of no benefit.
This study shows that patients can be rapidly switched from morphine to methadone; however, this approach failed in 16% of patients. Methadone may be associated with less constipation and dry mouth, and may be a good pain control option for patients with these problems. Acetaminophen did not improve pain control with this switching process.