Simplifying Opioid Conversions

by Drew Rosielle (@drosielle)A Satirical Monologue in One Act:“Ok, 3rd year resident, let’s talk about rotating opioids. What do I mean by ‘rotating’ opioids? It’s just therapeutically switching one opioid with another. It’s um, like, a turnstile, I guess? Anyway--first let’s look at this equianalgesic table. Do you know what equianalgesia means? No? It is the concept that different opioids have the same analgesic power but at different milligram doses due to different potencies. That is, the idea that, say, 50 mg of oral morphine has the same analgesic power as 10 mg of hydromorphone. So 50 mg of oral morphine is equivalent to 10 mg of ora l hydromorphone." Ok, let ’s look at this table, every entry on this grid is equianalgesic, meaning that the 30 mg here of oral morphine has the same analgesic power as the 1.5 mg of IV hydromorphone. So, let’s say we have a patient on 100 mg oral morphine. How much hydromorphone is that “equivalent” to? Ok, so what we have to do is set up a cross multiplication problem…here’s how you do that.[We ’ll skip the painful talk-through of the cross multiplication.]" Ok, so it looks like the answer is 20 mg of hydromorphone IV. Now we have to adjust that dose for incomplete cross-tolerance. Do you know what that is? No? Ok, so incomplete-cross tolerance is the idea that our patient on 100 mg of morphine is somewhat tolerant to the morphine. They are therefore also presumably somewhat tolerant to any other opioid agonis...
Source: Pallimed: A Hospice and Palliative Medicine Blog - Category: Palliative Care Tags: opioid rosielle Source Type: blogs