Dissociative-like Neurotoxicity Following Analytically Confirmed Exposure To Hexahydrocannabinol (HHC)

Hexahydrocannabinol (HHC) is a semi-synthetic hydrogenated derivative of delta-9-tetrahydrocannabinol (THC). HHC emerged within global markets in 2021and has been detected within unregulated cannabis products.

A 32-year-old male presented to hospital 1.5 h following ingestion of a single gummy, which had been sold as a THC product. Symptoms included nausea, vomiting, slurred speech, a subjective feeling of whole-body numbness, and an inability to move his head. Examination revealed an apparent dissociative state, sinus tachycardia (118 beats per minute), mydriasis, confusion, and tachypnoea (24 breaths per minute). There was no objective focal neurological deficit. Investigations including haematology and biochemistry were normal. Management was supportive and symptoms resolved within eight hours of ingestion. Serum analysis revealed the HHC isomers 9R-hexahydrocannabinol (9R-HHC) and 9 S-hexahydrocannabinol (9 S-HHC). No other pharmaceutical or psychoactive substance was detected.

HHC can be manufactured using cannabidiol as a precursor and can be administered via inhalation, orally and sublingually. The 9R-HHC isomer is the primary psychoactive component. HHC is rapidly absorbed, crosses the blood-brain-barrier and is hepatically metabolised. User reports of HHC adverse effects include anxiety, nausea, and "paralysing effects". Cases of HHC exposure reported in the literature describe palpitations, chest tightness, 'respiratory pause', seizures, dysarthria, dyskinesia, hallucinations, mydriasis, myalgias and acute psychosis. This case of analytically confirmed HHC exposure describes multi-system toxicity including gastrointestinal effects, and dissociative-like neurological effects, and serves as a reminder of the dangers of unregulated products sold within the illicit drug market.