Anesthesia: Those who smoke cannabis need a higher dose

Christiane Fux studied journalism and psychology in Hamburg. The experienced medical editor has been writing magazine articles, news and factual texts on all conceivable health topics since 2001. In addition to her work for, Christiane Fux is also active in prose. Her first crime novel was published in 2012, and she also writes, designs and publishes her own crime plays.

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Anyone who undergoes an operation is asked beforehand how much nicotine and alcohol they consume - and whether they use other drugs. You shouldn't be dizzy - because the consumption of drugs can make the anesthetic less effective. This relationship has been known for a long time, especially for alcohol.Now a study has also proven the phenomenon in people who regularly consume cannabis.

Significantly higher dose required

Scientists around Dr. Mark A. Twardowski of Western Medical Associates in Grand Junction, Colorado, looked at the anesthetic needs of a total of 250 patients during an endoscopic procedure. These interventions were carried out in Colorado between January 2016 and December 2017, where cannabis use was already legal at the time. 25 of the participants stated that they used cannabis regularly - that is, weekly to daily.

Cannabis users required a 14 percent higher dose of the anesthetic fentanyl than non-users; the dose of midazolam is almost 20 percent higher and of the anesthetic P even more than 220 percent more. It didn't matter how the cannabis was consumed, for example as a joint or in the form of hash cookies.

Mechanism still unknown

It is not yet known which biochemical mechanisms cannabis users require higher doses of anesthetics. The effects of the body becoming accustomed to cannabis, which then also extends to anesthetics, are discussed.

For example, the substances could be broken down more quickly. Or the body develops fewer receptors to which cannabis and anesthetics can dock - the latter then work worse from the outset. “Cannabis has some metabolic effects that we still understand. Patients need to know that cannabis can make other drugs less effective, ”says Twardowski.

Wake up on the operating table?

It is unclear whether the increased need for anesthetic increases the risk of not being sufficiently sedated during the procedure and thus experiencing the operation, but above all the pain associated with it. Because that is extremely rarely the case. As a rule, the anesthetist notices when the anesthesia is weakening due to stress reactions on the part of the patient such as an accelerated heartbeat, altered brain waves or perspiration. In such cases, the anesthetist can re-dose in good time.

Basically, it is known that higher amounts of anesthetic are associated with a higher risk of side effects. Study leader Twardowski says: "This is especially dangerous because a reduced respiratory function is a possible side effect."

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