<p>At least the 100 number seems based on the CDC <a href="https://www.mdanderson.org/documents/for-physicians/algorithms/clinical-management/clin-management-post-op-pain-web-algorithm.pdf" rel="nofollow noreferrer">parenteral dose conversion</a>:</p>

<p><a href="https://i.sstatic.net/s2mnP.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/s2mnP.png" alt="enter image description here"></a></p>

<p>(Fentanyl has poor oral bioavailability, so it's not intended to be used that way.)</p>

CC BY-SA 4.0
2019-05-12T16:58:12.930Z
2019-05-12T16:58:12.930Z
got trolled too much this week
<p><a href="https://www.dea.gov/factsheets/fentanyl" rel="nofollow noreferrer">E.g.</a></p>

<blockquote>
  <p>Fentanyl is a synthetic opioid that is 80-100 times stronger than morphine. </p>
</blockquote>

<p>What does that refer to?</p>

<p>According to <a href="https://en.wikipedia.org/wiki/Potency_(pharmacology)" rel="nofollow noreferrer">https://en.wikipedia.org/wiki/Potency_(pharmacology)</a>:</p>

<blockquote>
  <p>The IUPHAR has stated that 'potency' is "an imprecise term that should always be further defined", for instance as EC50, IC50, ED50, LD50 and so on.</p>
</blockquote>

<p>I guess <a href="https://en.wikipedia.org/wiki/Effective_dose_(pharmacology)" rel="nofollow noreferrer">effective dose</a> is the relevant notion here, but which version does the DEA use ED50, ED95 (does it matter which)?</p>

<p>Presumably they are not talking about <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0197734" rel="nofollow noreferrer">receptor affinity</a> which would be mostly irrelevant from DEA's perspective (although the FDA suggests otherwise). The latter ratio between fentanyl and morphine is only 1.35 to 1.14 on the μ-opioid receptor. Even that is not really a good way to compare, because actual measurements of affinity have a large margin of error:</p>

<p><a href="https://i.sstatic.net/j7mPl.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/j7mPl.png" alt="enter image description here"></a></p>

CC BY-SA 4.0
2019-05-12T16:47:33.160Z
Apparently the CDC itself [has been criticized](https://www.medpagetoday.com/painmanagement/painmanagement/50722) for making weaker/stronger-than-morphine comparisons. But let's take one claim at a time.
got trolled too much this week
<measurement><psychopharmacology>
When the DEA says a drug is X times more potent than another, what do they mean?
got trolled too much this week
# When the DEA says a drug is X times more potent than another, what do they mean?

(Asked by: username_0 on 2019-05-12)

[E.g.](https://www.dea.gov/factsheets/fentanyl)

> Fentanyl is a synthetic opioid that is 80-100 times stronger than morphine.

What does that refer to?

According to <https://en.wikipedia.org/wiki/Potency_(pharmacology)>:

> The IUPHAR has stated that 'potency' is "an imprecise term that should always be further defined", for instance as EC50, IC50, ED50, LD50 and so on.

I guess [effective dose](https://en.wikipedia.org/wiki/Effective_dose_(pharmacology)) is the relevant notion here, but which version does the DEA use ED50, ED95 (does it matter which)?

Presumably they are not talking about [receptor affinity](https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0197734) which would be mostly irrelevant from DEA's perspective (although the FDA suggests otherwise). The latter ratio between fentanyl and morphine is only 1.35 to 1.14 on the μ-opioid receptor. Even that is not really a good way to compare, because actual measurements of affinity have a large margin of error:

[![enter image description here](https://i.sstatic.net/j7mPl.png)](https://i.sstatic.net/j7mPl.png)

**Tags:** measurement, psychopharmacology

> **Comments:**
> **username_0**: Apparently the CDC itself [has been criticized](https://www.medpagetoday.com/painmanagement/painmanagement/50722) for making weaker/stronger-than-morphine comparisons. But let's take one claim at a time.  

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## 1 answers

### Answer by username_0 on 2019-05-12. Score: 2

At least the 100 number seems based on the CDC [parenteral dose conversion](https://www.mdanderson.org/documents/for-physicians/algorithms/clinical-management/clin-management-post-op-pain-web-algorithm.pdf):

[![enter image description here](https://i.sstatic.net/s2mnP.png)](https://i.sstatic.net/s2mnP.png)

(Fentanyl has poor oral bioavailability, so it's not intended to be used that way.)


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