Pepper spray is all over the news, following the Occupy Wall Street protests, particularly following the widely disseminated images and videos of protestors being sprayed in NY, Portland, and UCDavis.

Before that, I knew and occasionally used its main ingredient, capsaicin, as a treatment for my patients with shingles, an extremely painful Herpes zoster infection. And I knew about the many of the serious side effects of pepper spray, well-described by Deborah Blum.

Recently though, other questions arose, like “How was this learned?”. So off I went, looking for clinical trials to see what, if anything, had been studied, beyond the individual patient, poison control, and toxicology reports. Here’s what I learned:

There are reports of the efficacy of capsaicin in crowd control, but little regarding trials of exposures. Perhaps this is because pepper spray is regulated by the Environmental Protection Agency, as a pesticide and not by the FDA.

The concentration of capsaicin in bear spray is 1-2%; it is 10-30% in “personal defense sprays.”

While the police might feel reassured by the study, “The effect of oleoresin capsicum “pepper” spray inhalation on respiratory function,” I was not. This study met the “gold standard” of clinical trials, in that it was a “randomized, cross-over controlled trial to assess the effect of Oleoresin capsicum (OC) spray inhalation on respiratory function by itself and combined with restraint.” However, while the OC exposure showed no ill effect, only 34 volunteers were exposed to only 1 sec of Cap-Stun 5.5% OC spray by inhalation “from 5 ft away as they might in the field setting (as recommended by both manufacturer and local police policies).”

By contrast, an ACLU report, “Pepper Spray Update: More Fatalities, More Questions” found, in just two years, 26 deaths after OC spraying, noting that death was more likely if the victim was also restrained. This translated to 1 death per 600 times police used spray. (The cause of death was not firmly linked to the OC). According to the ACLU, “an internal memorandum produced by the largest supplier of pepper spray to the California police and civilian markets” concludes that there may be serious risks with more than a 1 sec spray. A subsequent Department of Justice study examined another 63 deaths after pepper spray during arrests; the spray was felt to be a “contributing factor” in several.

A review in 1996 by the Division of Epidemiology of the NC DHHS and OSHA concluded that exposure to OC spray during police training constituted an unacceptable health risk.

Surveillance into crowd control agents examined reports to the British National Poisons Information Service, finding more late (>6 hour) adverse events than had been previously noted, especially skin reactions (blistering, rashes).

Studies have, understandably, more looked at treatment than at systematically exploring toxic effects of pepper spray. An uncontrolled California Poison Control study of 64 patients with exposure to capsaicin (as spray or topically as a cream) showed benefit with topically applied antacids, especially if applied soon after exposure.

In a randomized clinical trial, 47 subjects were assigned to a placebo, a topical nonsteroidal anti-inflammatory agent, or a topical anesthetic. The only group with significant symptomatic improvement in pain received proparacaine hydrochloride 0.5%--and only 55% had decreased pain with treatment.

Another randomized controlled trial looked at 49 volunteers who were treated with one of five treatment groups (aluminum hydroxide–magnesium hydroxide [Maalox], 2% lidocaine gel, baby shampoo, milk, or water). There was a significant difference in pain with more rapid treatment, but not between the groups.

I was most impressed with the efforts of the Black Cross Health Collective in Portland, Oregon. These activists have been thoughtfully approaching studying treatments for pepper spray exposures with published clinical trial protocols, where each volunteer also serves as their own control. Capsaicin is applied to each arm; a “subject-blinded” treatment is applied to one arm, and differences in pain responses are recorded. I love that they are looking for evidenced based solutions.

So far, antacids have been the most effective.

Suggestions for further study

Pepper spray causes inflammation and swelling—particularly a danger for those with underlying asthma or emphysema. In fact, the Department of Justice report notes that in two of 63 clearly documented deaths, the subjects were asthmatic. If they don't already, police need to have protocols in place to identify and treat "sprayees" who have these pre-existing conditions that predispose them to serious harm from the spray. This particularly holds true for people also at risk for respiratory compromise from being restrained, on other drugs, or with obesity. The study of restrained healthy volunteers exposed to small amounts of capsaicin is simply not applicable to the general population. Also, given that these compounds appear to have delayed effects, there should be legally required medical monitoring of "sprayees" at regular and frequent intervals for at least 24 hours—by someone competent. (Iraq war veteran Kayvan Sabehgi could easily have died from the lacerated spleen sustained in his beating by police. It was 18 hours before he was taken to the hospital, after the jail’s nurse reportedly only offered him a suppository for his abdominal pain. There is also an, as yet unconfirmed report, of a miscarriage after the Portland, Oregon OWS protest last week).

Unfortunately, there is an urgent need for clinical trials in this area—both retrospective assessments of "sprayees" health outcomes, and prospective randomized trials [like the trial done on subjects' arms] to elucidate the effects of various capsaicin concentrations, carrier solvents and propellents and to identify the most effective treatments for each mixture. Until those can be done, there should be a thorough outcomes registry kept, with standardized data being obtained on all those subsequent to being pepper-sprayed.

Sadly, I’m sure the Black Cross and others in the Occupy Wall Street movement will have too many opportunities to test therapies against painful crowd-control chemicals. Studies will be difficult because the settings are largely uncontrolled and because the sprays have different concentrations of capsaicin, carrier solvents, and propellants.

Until then, there should be a moratorium on the use of pepper spray or other “non-lethal” chemicals by police, except in clearly life-threatening confrontations, due to the high number of associated deaths until the risks are better understood?

Perhaps Kamran Loghman, who helped the FBI weaponize pepper spray, will be dismayed enough at the “inappropriate and improper use of chemical agents” to help the Black Cross develop effective antidotes…One can only hope.

Image credits: Image 1 by Brian Nguyen from The California Aggie via BoingBoing (CC with attribution); Image 2 from FreakOutNation; Image 3 from mellowed blues.

Previously in this series:

Molecules to Medicine: Clinical Trials for Beginners

Molecules to Medicine: From Test-Tube to Medicine Chest

Lilly’s Shocker, or the Post-Marketing Blues

Molecules to Medicine: Pharma Trumps HIPAA?

Related at Scientific American:

About Pepper Spray

Why One Pepper-Spraying Cop Image Dominates

Protest Infrastructure: How Much Trouble Are Protesters, Really?

How Valid Are Health Concerns for the Occupy Wall Street Camps?

Dear Occupy Wall Street: Read Jeffrey Sachs!

“Occupy Wall Street” Passes Near Scientific American‘s Office in New York City

The "Last Place Aversion" Paradox: The surprising psychology of the Occupy Wall Street protests