Median prior morphine dose for the entire sample was 220 mg/day (range: 30–1000 mg/d). Initial MMEDR was 5:1 or 10:1 in 82% and 18% of patients, respectively. The stable median MMEDR at Day 10 was 5:1 (range: 2:1–15:1). Multiple linear regression analysis showed that the reason for switching (pain vs. side effects) and prior morphine dose (less than 300 mg/d vs. 300 or more mg/d) were significantly (p < .001) associated with the stable MMEDR. Therefore, these are predictive factors for more accurately selecting an appropriate conversion ratio (as shown in the Table below).
Caution: These ratios apply only to opioid-tolerant patients and are somewhat lower than those reported elsewhere in the literature. The same conversion factors should NOT be used in reverse, as when converting from methadone to morphine.Reference: Benítez-Rosario MA, Salinas-Martín A, Aguirre-Jaime A, Pérez-Méndez L, Feria M. Morphine-methadone opioid rotation in cancer patients: analysis of dose ratio predicting factors. J Pain Symptom Manage. 2009(Jun);37(6):1061-1068.
Also see…
> Rotation From Other Opioids to Methadone Reviewed. Pain-Topics Updates, 2008;16.
> Toombs JD. Oral Methadone Dosing for Chronic Pain: A Practitioner's Guide. Pain Treatment Topics, 2008(Mar).
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5 comments:
What type of a conversion ratio or morphine equivalent dose are you using when switching from methadone to morphine in a patient who has been receiving methadone for chronic pain.
In response to the question above -- according to the literature, numerous factors may influence the safety and tolerability of rotations from methadone to other opioids, including: patient age or gender, expected pain control, existing disease, concomitant medications, and genetic influences. For some preliminary recommendations on equianalgesic dosing, see the article, “Conversion Ratios for Rotation from Methadone to Other Opioids” in our “e-Briefing Newsletter” (2006, Vol 1, No 2, page 10). Go to: http://pain-topics.org/pdf/e-Briefing_Vol1_No2_2006.pdf (copy & paste link into your browser).
In reference to the article “Conversion Ratios for Rotation from Methadone to Other Opioids” in your “e-Briefing Newsletter” (2006, Vol 1, No 2, page 10). Go to: http://pain-topics.org/pdf/e-Briefing_Vol1_No2_2006.pdf and the primary article by Walker PW et al, 2008 Switching from methadone to a different opioid: what is the equianalgesic dose ratio? The ratio of oral methadone to oral morphine of 1:4.7 does not appear to apply to a patient who has been chronically receiving methadone since this study criterion involved "patients who had received methadone for at least 3 days or more". The definition of "more" was not included in the study. Therefore, it would seem likely that the patient had not reached analgesic stability on methadone at 3 days of treatment. This is assuming a half life of 30 hours which would likely be longer if the patient had received methadone long-term. Walker et al, 2008 conclude that "it would be judicious to rotate patients in clinical practice from methadone to other opioids using conversion dose ratios more conservative than described in their paper" (1:4.7). One of the limitations listed is the need for a longer period of methadone administration before rotation, and reporting of dosages of other opioids at longer follow up may be beneficial in more accurately calculating the equianalgesic dose ratios. Therefore, it would seem prudent to use a ratio for oral methadone to oral morphine of between approximately 1:8 to 1:11 as reported is some case reports by Lawlor et al, 1997 and Ripamonti et al, 1998. These reports were in patients with cancer. However, if treating chronic non-cancer pain it seems that this may also be the approach.
If possible, I would like to hear some response on the conclusion above "Therefore, it would seem prudent to use a ratio for oral methadone to oral morphine of between approximately 1:8 to 1:11 as reported is some case reports by Lawlor et al, 1997 and Ripamonti et al, 1998. These reports were in patients with cancer. However, if treating chronic non-cancer pain it seems that this may also be the approach." Are other providers in agreement with this?
If I read the information correclty, then we would want to be more conservative when switching form Methadone to morphine so the conversion ration would not be 1:8 to 1:11 but would be even lower than the 1:4.7 conversion listed by Walker PW et al, 2008. Therefore, would it be recommended to possibly use a conversion ration of 1:1 to 1:3 when converting from methadone to morphine as to not over estimate the potency of methadone?
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