grayanotoxins

Grayanotoxins are a group of naturally occurring diterpenoid neurotoxins known as grayananes. They occur in certain Rhododendron species, notably Rhododendron ponticum and Rhododendron luteum, and can be present in honey produced from the nectar of these plants, commonly called mad honey. The grayanane family includes grayanotoxins I–IV and related compounds such as andromedotoxin.

The toxins affect voltage-gated sodium channels in neurons, binding to sites on the channel and causing persistent activation and sustained depolarization. This disrupts normal nerve signaling and autonomic function, leading to a range of symptoms.

Most human exposure results from ingestion of plant material or honey containing grayanotoxins. Onset is typically 30 minutes to several hours after exposure and can include dizziness, nausea, vomiting, abdominal pain, excessive salivation, hypotension, bradycardia, flushing, weakness, and syncope. In some cases, seizures or reduced consciousness may occur. The syndrome is usually self-limited, with symptoms resolving within 12–24 hours, though cardiovascular instability may require medical care.

There is no specific antidote. Management is supportive and may involve intravenous fluids, electrolyte correction, and, if necessary, vasopressor therapy or atropine for severe bradycardia. Patients are commonly monitored to ensure symptom resolution. Prevention focuses on avoiding grayanotoxin-containing products, particularly mad honey from endemic regions.