Cannabis Users Show Reduced Response to Anesthetics and Opioid Painkillers

Researchers at the University of Colorado Hospital in the United States have conducted the world’s first study on how cannabis use affects sensitivity to anesthetics and opioid painkillers. The study found that smoking cannabis dulls the body’s response to these types of medications.

Cannabis Users Require Higher Doses of Medication

The study involved 118 patients undergoing surgery to repair a fractured tibia. Thirty participants reported using cannabinoids shortly before hospitalization. Doctors compared the medication response between cannabis users and non-users.

During surgery, anesthesiologists monitored pain based on four indicators: involuntary body movements, increased heart rate, high blood pressure, and rapid breathing. During the recovery period, attending physicians assessed pain intensity on a scale from 0 to 10 (0 – no pain, 1-3 – mild pain, 4-7 – moderate pain, 8-10 – severe pain).

After analyzing the data, doctors found that:

• Cannabis smokers required 50% more of the anesthetic sevoflurane (37.4 ml vs. 25 ml).
• During post-surgery recovery, cannabis users reported 25% higher pain intensity (6 vs. 4.8 points).
• During rehabilitation, cannabis users took 58% more morphine (155.9 mg vs. 98.6 mg per day).

Cannabis May Cause Tolerance to Analgesics and Sedatives

Project leader Ian Holmen commented on the results: “Cannabis helps with chronic and neuropathic pain, but it does not relieve acute pain caused by surgery. We know that patients who regularly use opioids develop a strong pain response after surgery and require higher doses of analgesics due to developed tolerance. Apparently, cannabis causes the same effect, but we need further research to confirm this.”

Last year, American scientists analyzed data from 250 people who underwent endoscopy and found that cannabis smokers had a suppressed response to sedatives and analgesics. As a result, doctors had to increase the dosage of medications: fentanyl by 14%, midazolam by 20%, and propofol by 220%.

Based on the results of studies from 2019 and 2020, researchers hypothesize that cannabis causes tolerance to three groups of drugs: anesthetics, sedatives, and analgesics. The main limitation of the U.S. studies is that experts did not determine the frequency and dosage of cannabinoid use among patients.