We’ve all observed the tell-tale sign that someone is high on fentanyl in that they’re bent over and frozen in the so-called “fentanyl fold,” and a new Chronicle report speaks to medical experts and users about why this happens.

The most troubling aspect of San Francisco’s fentanyl crisis is the more than 800 people who died from drug overdoses last year, and of those, around 80% involved the use of the deadly opioid fentanyl. This is a national problem, and not at all exclusive to San Francisco.

But given the national media obsession with bashing San Francisco, it’s frequently pointed out that fentanyl users are often hunched over on SF streets. This too happens in other cities across the US, but there’s a lot of media focus on calling out SF for it, as seen in the Sky News report below on the “drug-ravaged Tenderloin.”

Today’s Chronicle takes a semi-scientific look into why people slouch over when using fentanyl. Turns out this happens to some degree with many other opioids, like heroin and oxycodone — the so-called "nod" one gets in an initial high. But since much of the fentanyl supply has become exponentially more powerful than heroin, the slouching effect is most pronounced with fentanyl.

“What you’re witnessing is the balance point between passing out,” UCSF professor of addiction medicine Dr. Daniel Ciccarone told the Chronicle. “When you lose all muscular control and are on the floor – versus some small remnant of consciousness that is keeping the person up-right.”

The "fentanyl fold" effect can reportedly kick in within two or three minutes after taking the drug. And oddly, users report the feeling is actually somewhat euphoric.

The Chronicle also spoke to several fentanyl users about the slouch, which gives insight into how people end up using the drug on the streets. One 50-year-old user Jeff Barlow had been a school teacher and motocross racing hobbyist, and required surgery after an accident. That got him hooked on painkillers, and he’s now on the streets of SF, sometimes slouched.

“You don’t even know you’re like that,” Barlow said to the Chronicle.

“It’s like falling asleep in class,” he added. “You blink your eyes and 20 minutes go by. You’re kind of half-in and half-out of consciousness.”

Yes, this can cause spinal disorders, as well as neck and back issues. The cruel irony is that some people use fentanyl for pain relief, which it provides in the short term, but the slouching can aggravate these medical issues in the long run.  

“I take it because it helps with the pain on my knee and my foot,” user Frederick Smith told the Chronicle. “But it makes everything worse.”

ABC 7 did a similar story in March about why fentanyl causes this particular bent-over reaction. One user they spoke to, who had taken the drug hours earlier but remained bent over, was asked if he was able to stand up straight. "I mean, I can, but it hurts a lot to have to do that," he said.

Researchers still don't know if fentanyl causes long-term effects on the spine, however there are signs that it causes major systemic and circulation issues. As ABC 7 learned from researchers, the thinking is that the acidic nature of the drug leads to the collapsing of veins. Additionally, fentanyl that is mixed with "tranq" or xylazine has been shown to cause terrible skin ulcers that can become infected.

Related: Walgreens Now Selling Cheaper Generic Narcan Over the Counter, and It’s Already Available [SFist]

Image: @citizenj17 via Twitter