Why Cannabinoids Can Both Prevent and Cause Vomiting: The Hyperemesis Paradox | Research

The takeaway

A review explored the paradox of cannabinoid hyperemesis syndrome, where chronic cannabis use causes cyclical vomiting despite cannabinoids being established anti-nausea drugs, proposing multiple pharmacokinetic and pharmacodynamic mechanisms.

Read this if you or someone you know experiences cyclical vomiting associated with cannabis use.

Anti-nausea drug paradoxically causes cyclical vomiting in chronic users

What the researchers found

Cannabinoids are clinically used as anti-nausea medications (preventing chemotherapy-induced vomiting through CB1 receptor stimulation), making the recently recognized cannabinoid hyperemesis syndrome (CHS) a paradox.

CHS is characterized by repeated cyclical vomiting and compulsive hot water bathing in chronic cannabis users. Though initially considered rare, increasing case reports suggested it was more common than thought.

The review proposed multiple potential mechanisms:

Pharmacokinetic: THC long half-life and fat solubility leading to accumulation, individual variation in metabolism/excretion, and buildup of emetogenic (vomiting-causing) metabolites.

Pharmacodynamic: THC switching from partial agonist to antagonist at certain levels, CB1 receptor desensitization or downregulation with chronic exposure, alterations in endocannabinoid concentrations, and differential effects in the brain versus the gut.

The review also noted that chronic exposure may not be necessary to trigger vomiting but is required for the intensity of emesis.

Why it matters

Understanding why an anti-emetic drug can paradoxically cause vomiting has implications for both clinical use of cannabinoid medications and for the millions of chronic cannabis users who could potentially develop this syndrome.

The numbers in context

International case reports were increasingly being published at the time. Multiple pharmacokinetic and pharmacodynamic mechanisms were proposed.

How the study worked

Narrative review examining basic science mechanisms that could explain cannabinoid-induced hyperemesis, integrating pharmacokinetic, pharmacodynamic, and clinical data.

What this study cannot tell us

No single mechanism has been definitively established. The review was based on case reports and basic science reasoning rather than direct experimental testing of proposed mechanisms. CHS prevalence was uncertain.

How to read the evidence

Narrative review proposing mechanistic explanations based on basic science and clinical observations. No mechanism has been definitively proven.

When this study was published

Published in 2010. CHS has since been widely recognized as a clinical entity, with clearer diagnostic criteria and management guidelines developed.

The bigger picture

CHS has become increasingly recognized since this review. Understanding the mechanism is important because CHS can cause severe dehydration, electrolyte imbalances, and repeated emergency department visits, and is often initially misdiagnosed.

Questions still open

Which mechanism is primary? Why do only some chronic users develop CHS? Why does hot water bathing provide relief? Can CHS be predicted or prevented in susceptible individuals?

Common questions

What is cannabinoid hyperemesis syndrome?

CHS is a condition in chronic cannabis users characterized by episodes of severe nausea and vomiting that occur in cycles, often accompanied by compulsive hot water bathing (which temporarily relieves symptoms). The only definitive treatment is stopping cannabis use.

If cannabis prevents nausea, how can it also cause vomiting?

The paradox may involve receptor desensitization (receptors becoming less responsive to chronic stimulation), accumulation of vomiting-inducing metabolites, or different effects in the brain versus the gut. The exact mechanism remains debated.

Read the original research

Cannabinoid-Induced Hyperemesis: A Conundrum-From Clinical Recognition to Basic Science Mechanisms.

Pharmaceuticals (Basel, Switzerland), 3(7), 2163-2177

View on PubMed ↗

Citation

Darmani, Nissar A. (2010). Cannabinoid-Induced Hyperemesis: A Conundrum-From Clinical Recognition to Basic Science Mechanisms.. Pharmaceuticals (Basel, Switzerland), 3(7), 2163-2177.