When Cannabis Makes You Projectile Vomit

The first thing Jason did after he checked into his ER room was to walk to the closet to grab a vomit basin. This was his eighth visit in two weeks and he knows where everything is. He practically lives in the ER.

"Sorry to see you so soon Jason, what brings you back?"

"The same thing," he sputtered.

"Vomiting again?"

"It just won't go away."

Jason (name changed for privacy), a late 30s, long-time cannabis smoker, has had every expensive test imaginable to diagnose his episodes of vomiting: CT scans, endoscopies, colonoscopies, biopsies, you name it. The vomiting comes in severe waves over two to three days, uncontrollable by the typical prescription strength anti-nausea medications he can take at home. Jason suffers from Cannabinoid Hyperemesis Syndrome (CHS): vomiting caused by marijuana.

To the lay smoker, and even physicians, the syndrome is perplexing, frustrating, and paradoxical. When patients are told their habitual joint lighting, bong ripping, or edible munching is the cause of their symptoms, most respond as though their world is crashing down around them.

"Wait what? Weed treats nausea!"

They do have a point. Cannabis has well known anti-nausea and appetite-stimulating properties; it is frequently prescribed to chemotherapy patients who are having difficulty just looking at food. The THC in cannabis activates the CB1 (cannabinoid 1) receptor, which tells neurons in the brain to stop releasing vomit-inducing chemicals.

The CHS triad was first described in 2004 as: 1) long-standing (at least weekly) use of cannabis, generally for more than five years, 2) severe cyclic nausea and vomiting, and 3) relief of symptoms with hot baths or showers and cessation of cannabis use. The exact cause of CHS is unknown, but is hypothesized to result from a buildup of cannabinoid compounds in the brain that leads to a "boy who cried wolf" phenomenon of the CB1 receptor: After being stimulated continuously for so long, the brain stops making the CB1 receptor, and even removes the CB1 receptor from the surface of neurons.

CB1 receptors are also located in the gut, where continuous activation will cause slowing of stomach and intestinal function; slow enough to cause a backup of food resulting in abdominal pain. Without the anti-nausea effects of the CB1 receptor in the brain, severe Exorcist-type vomiting ensues, the type that will echo through a whole ER. Multiple doses of the traditional nausea medications like ondansetron and metoclopramide may or may not help.

Often the medical attention provided in the ER only partially improves symptoms. Patients are either sent home with continued vomiting and instructions to stop smoking, or have to be admitted to the hospital, where after three to four days sans THC, they improve. Sadly most patients will be seen over and over again, quickly accumulating a hefty medical bill. Rarely, it can take a month for symptoms to fully abate, but that might be because patient's can't resist another toke.

Large epidemiological studies of CHS do not exist yet, but two hospitals in Colorado have seen ER visits for CHS almost double since legalization of medical marijuana in 2009. This is the result of increased use of cannabis and increased potency of modern products. The modern cannabis flower typically averages 6-8 percent THC, whereas 1960s "Hippie Weed" averaged just 1 percent.

But what's with the hot-showers? Rodent studies have showed that THC will cause the hypothalamus, the thermostat of the brain, to think the body is too cold. A hot shower will counteract this, but also help treat a contemptuous stomach by redistributing blood from the gut to the skin, decreasing intestinal inflammation. Human patients generally stumble upon this realization themselves, and will bathe four to five times a day, and only arrive at the ER after using up all the hot water at home.

Frequent hot showers are such a hallmark of the disease that Jeff Lapoint, a toxicologist at Kaiser Permanente San Diego, conducted his own brilliantly insightful yet comical medical study. Lapoint had previously come a cross a receptor in the body, TRPV1, that is activated by only two things: scalding heat hotter than 109 degrees Farenheit and capsaicin, the compound in hot sauce that produces the familiar burn. Knowing this, Lapoint hypothesized that slathering capsaicin cream on the belly of his suspected CHS patients would improve symptoms. The symptoms in all seven of his patients either resolved or dramatically diminished within 30 to 45 minutes.

While the size of the study was tiny and the results have not been validated by other physicians, it might be a good idea for habitual cannabis smokers to stock up on Cholula, and not just for breakfast burritos, but to save them a costly visit to the ER.

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Darragh O'Carroll, MD, is an emergency physician in Hawaii.