Even in states where marijuana is legal, some patients may feel reluctant to tell their doctors exactly how much they smoke. But per a report in the Journal of the American Osteopathic Association, having that honest conversation may be even more important than it seems. Marijuana’s side effects could have consequences for patients undergoing medical procedures.

In the paper, released Monday, Mark Twardowski, a doctor of osteopathic medicine affiliated with Grand Junction, Colorado’s Community Hospital, reports that patients who regularly smoked marijuana required as much as 220 percent more anesthetic chemicals to become fully sedated — a relaxed, but not fully unconscious state. This too-chill side effect, he and his co-authors argue in the paper, could have serious consequences, requiring doctors to up the dosage of chemicals like fentanyl, midazolam, and propofol. Those are drugs usually used to help knock patients out before procedures like colon cancer screenings.

Importantly, the sedatives Twardowski analyzed were all used legally, for medical reasons. It’s just that patients who “regularly smoked weed” seemed to require a lot more of these chemicals to go under than they should have needed.

“We were surprised by the extent and consistency of the effect that cannabis use had on the increasing doses needed to achieve adequate sedation for the procedures,” he tells Inverse. “One of our great hopes of this study is that we will create awareness that the effects of some medications are distinctly affected by cannabis use.”

Patients who regularly smoke weed may need higher doses of anesthetics to get the same effects. Unsplash

Twardowski analyzed the records of 250 randomly chosen patients who went in for endoscopic exams — the procedure used during a colonoscopy, where a doctor inserts a camera into the intestine — at a Colorado hospital. Only 25 of those patients smoked or ingested cannabis on a daily or weekly basis, but Twardowski noticed a significant pattern in the amount of sedatives used in their procedures. On average, those patients required 14 percent more fentanyl to get to sleep, 19.6 percent more midazolam, and 220.5 percent more propofol to achieve the correct level of drowsiness for their colon exams.

This study only looked at past medical records — so it’s hard to narrow down exactly what it is about cannabis that creates this association. But in the paper, Twardowski makes the argument that it comes down to lingering neurological effects of marijuana use that may blunt the impact of sedatives. These hypotheses hinge on THC, the chemical that induces marijuana’s psychoactive effect.

Cannabis users required higher levels of sedatives to get knocked out before endoscopic screenings. Journal of the American Osteopathic Association/ Twardowski

THC interacts with many different cannabinoid receptors in the brain — which impact functions like memory, mood, and pain sensation. In the paper, Twardowski writes that THC may also “interact with specific cannabinoid receptors, which could include opioid and benzodiazepine receptors,” the same targets in the brain that these anesthetic chemicals use to achieve their sedative effects.

It’s unclear what he means by “interact” at this point, but the takeaway right now is that there’s something going on in the brains of regular cannabis users that makes it more difficult for the sedatives to start working.

“We and others suspect that the effect lies at the receptor level, possibly through some sort of down-regulation, but the specifics are not known,” Twardowski says. “Unfortunately, the basic science has not really been done on this or many issues around cannabis. This is largely due to the federal designation as a Schedule I drug.”

"Unfortunately, the basic science has not really been done on this or many issues around cannabis."

Identifying a biological explanation for this effect could go a long way toward finding a way around increasing sedative doses. But in the meantime, Twardowski makes it clear the big takeaway is that it’s worth confiding to a doctor about marijuana use even if it’s a tricky conversation to have.

This study was conducted in Colorado, where both medical and recreational marijuana are legal, but marijuana is still tightly controlled in some states. And even in places where it’s legal, stigma around the drug — it’s still Schedule I, after all — makes it harder for patients to be honest about using it. Making doctors aware of what other substances may be affecting the body, Twardowski adds, may allow them to provide better care when it comes to putting someone under.

It’s already hard enough to get people to participate in colon exams, but making sure they have all the sedative levels right can go a long way in making an uncomfortable process more manageable. This study just provides more evidence showing that disclosure is the best policy.

Partial Abstract:

Objective: To determine whether regular cannabis use had any effect on the dose of medication needed for sedation during endoscopic procedures.

Methods: A total of 250 medical records were reviewed from 1 endoscopy center and 1 endoscopist to minimize the variability in sedation technique for the study purposes. The cohort was reviewed with regard to age and gender to determine whether differences were present among different groups as to the relative amount of sedation medication required in cannabis users vs nonusers.

Results: Medical records from 250 patients were reviewed, and researchers found that compared with people who did not regularly use cannabis, people who regularly used cannabis required an amount of sedation for endoscopic procedures that was significantly higher (P=.05). The statistical significance persisted when adjusted for age, sex, and use of alcohol, benzodiazepines, and opiates.

Conclusion: Determining cannabis use before procedural sedation can be an important tool for planning patient care and assessing both medication needs and possible risks related to increased dosage requirements during endoscopic procedures.