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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10 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?
I actually have a question. I have a friend in the hospital undergoing chemo and radiation for esophogus cancer. He is and has been a methadone patient (for opiate addiction) for 3 years. He's on 125 mgs of Methadone a day and they are giving him a little extra for pain. They did have him on Dilaudid and Morphine in addition to the Methadone but has stopped the Dilaudid and Morphine and is having alot of pain now. They said he was on too much other opiates in addition to the Methadone. My question is: What would be enough for pain control? Should he still be on the Morphine/ Dilaudid in addition to the Methadone or should they try the Fentanyl patch or IV Methadone? Any help or advise would be greatly appreciated. I have looked on the internet and can't find any comparable answer.
The question immediately above is important; however, we cannot respond (nor will we allow others to respond) to questions regarding individual patient health concerns. We cannot know all details of the patient's particular history and current status. And, we believe that second-guessing the clinical judgment of practitioners without knowing all of the details is inappropriate and can be very hazardous. -- SBL
Regarding the earlier comments above about conversion ratios... there seems to be some confusion about morphine-to-methadone vs methadone-to-morphine ratios, and they are not interchangeable. We do not clearly understand what the comment authors are trying to say and we advise other readers to be cautious. Also, the usual time required to attain stability on methadone is 4 to 5 days but it can be much longer in some patients due to variations of individual metabolism. -- SBL
It may be prudent to access the conversion software available from the John Hopkins site if wanting to know conversion/switching to different opiates www.hopweb.org/. Their software programme gives instant conversion ie. 30mg oral methodone would equal 90mg morphine sulphate oral sustained release. It is worth a note- methodone(physeptone) has a 24 hour half life and is usually prescribed as a 24 hr dose in opiate maintenance however for pain relief this would be better split.
Thank you, for the note immediately above. We have also discussed opioid conversion and rotation issues in another blogpost [here], noting among other things that all of the automated conversion calculators have their own quirks and limitations that must be cautiously taken into account. To reinforce the message above, methadone is never prescribed once-daily for analgesia; rather it is split into multiple doses and it is vital that patients be monitored very closely for at least several days after starting methadone or after any increase of dose.
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