Rhinorrhea is decreased in dogs after nasal application of botulinum toxin

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Abstract
At this time no effective long‐term therapy exists for the excessive secretion of vasomotor rhinitis. Because rhinorrhea is under parasympathetic control, it was theorized that botulinum toxin ‐ a powerful and long‐acting cholinergic blocker that has been successful in the treatment of dystonia ‐ might be useful in blocking the cholinergic control of rhinorrhea. Four male mongrel dogs were studied. Fifty units of type A botulinum toxin was soaked into sterile gauze, which was then packed into the left nasal cavity of each dog for 1 hour. Saline‐soaked gauze was similarly introduced into the right nasal cavity to serve as control. Six days later, rhinorrhea was produced by inserting a bipolar needle electrode into the sphenopalatine ganglion and electrically stimulating for 10 minutes (6 mA, 50 Hz). Nasal secretions were collected with a suction catheter placed in the nasal vestibule. Three of four dogs exposed to the toxin showed a 41% average decrease in rhinorrhea (specifically 53%, 41%, and 30%). One dog showed a 10% increase in secretion after exposure to the toxin. We conclude that topically applied botulinum toxin reduced neurally evoked rhinorrhea by an average of 41%. Because some secretion is mediated by noncholinergic neurotransmitters such as vasoactive intestinal peptide, topical application of an anticholinergic substance has limitations. However, because all the nasal parasympathetic nerves appear to originate from cholinergic synapses in the sphenopalatine ganglion, direct injections of toxin into this ganglion may possibly allow complete blockade of all cholinergically mediated rhinorrhea.