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Grayanotoxin (formerly known as andromedotoxin, acetylandromedol, and rhodotoxin) causes ‘honey intoxication'. Honey intoxication is very rare and is caused by the consumption of honey produced from the nectar of rhododendrons. The grayanotoxins cause the intoxication. The specific grayanotoxins vary with the plant species. These compounds are diterpenes, polyhydroxylated cyclic hydrocarbons that do not contain nitrogen.
Other names associated with the disease is rhododendron poisoning, mad honey intoxication or grayanotoxin poisoning.
Grayanotoxin poisoning in humans is rare. However, cases of honey intoxication should be anticipated everywhere.
The intoxication is rarely fatal and generally lasts for no more than 24 hours. Generally the disease induces dizziness, weakness, excessive perspiration, nausea, and vomiting shortly after the toxic honey is ingested. Other symptoms that can occur are low blood pressure or shock, bradyarrhythima (slowness of the heart beat associated with an irregularity in the heart rhythm), sinus bradycardia (a slow sinus rhythm, with a heart rate less than 60), nodal rhythm (pertaining to a node, particularly the atrioventricular node), Wolff-Parkinson-White syndrome (anomalous atrioventricular excitation) and complete atrioventricular block.
The grayanotoxins bind to sodium channels in cell membranes. These compounds prevent inactivation; thus, excitable cells (nerve and muscle) are maintained in a state of depolarization, during which entry of calcium into the cells may be facilitated. This action is similar to that exerted by the alkaloids of veratrum and aconite. All of the observed responses of skeletal and heart muscles, nerves, and the central nervous system are related to the membrane effects.
Because the intoxication is rarely fatal and recovery generally occurs within 24 hours, intervention may not be required.
Grayanotoxin poisoning most commonly results from the ingestion of grayanotoxin-contaminated honey, although it may result from the ingestion of the leaves, flowers, and nectar of rhododendrons. Not all rhododendrons produce grayanotoxins. Rhododendron ponticum grows extensively on the mountains of the eastern Black Sea area of Turkey. This species has been associated with honey poisoning since 401 BC. Other species of rhododendrons and other members of the botanical family Ericaceae , to which rhododendrons belong may produce the toxins, but are not often implicated with the disease. Mountain laurel (Kalmia latifolia ) and sheep laurel (Kalmia angustifolia ) are probably the most important other sources of the toxin.
The increased desire of the public for natural (unprocessed) foods, may result in more cases of grayanotoxin poisoning. Individuals who obtain honey from farmers who may have only a few hives are at increased risk, especially when the honey may have been collected from the plants mentioned above. The pooling of massive quantities of honey during commercial processing generally dilutes any toxic substance.
All people are believed to be susceptible to honey intoxication.
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