Ciguatera fish poisoning: a double-blind randomized trial of mannitol therapy

Ciguatera poisoning (CP) is worldwide the most common fish-borne illness and one of the most common forms of nonbacterial food poisoning. IV mannitol is considered the treatment of choice for CP but has not been evaluated in a double-blind randomized trial.

A prospective clinical study of 50 patients with CP on Rarotonga, Cook Islands, was conducted to better define the neurologic picture of CP and to study the effect of mannitol or normal saline under double-blind randomized conditions over a 24-hour period.

The neurologic presentation of CP was that of a predominantly sensory, length-dependent polyneuropathy, with preferential small-fiber involvement. Motor paresis, cranial nerve dysfunction, and CNS abnormalities were absent but for a rare mild transitory cerebellar syndrome. At 24 hours, 96% of mannitol-treated patients and 92% of normal saline-treated patients had some improvement of symptoms (p = 1.0), whereas 12% and 24% of patients in each group were asymptomatic (p = 0.46). By 24 hours, the prevalence of the various polyneuropathic symptoms and signs was reduced roughly by half in both groups. Discomfort or pain along the vein used for infusion was more frequent in the mannitol group (84%) than in the normal saline group (36%) (p = 0.0015).

Mannitol was not superior to normal saline in relieving symptoms and signs of CP at 24 hours in this study population but had more side effects. These results do not support single-dose mannitol as standard treatment for CP.