Ocean Watch

By Susan Scott

Monday, August 12, 1996


Ciguatera fish poisoning
remedied by new drug

Several years ago, a Marshall Islands newspaper editor wrote to me about ciguatera fish poisoning.

"Please tell your readers about the new mannitol treatment," he wrote. "It has saved lives here."

I knew where this editor got his information since the physician who discovered it, Neal Palafox, now practices in Wahiawa.

So I called Dr. Palafox to find out the most recent information about mannitol as a treatment for ciguatera poisoning.

"It looks good, but the jury's still out," he said. "We're in the middle of doing a randomized, double-blind clinical study."

Such controlled studies are crucial in medicine, where the placebo effect can account for a whopping 30 percent of "cures" or other favorable results.

In the mysterious world of the placebo effect, patients and doctors unintentionally sway the results of a treatment by their own perceptions of what the outcome should be.

If a doctor, for instance, tells a patient that a shot will make him feel better, up to 30 percent of the time it will, even if it's plain water.

Also, doctors' beliefs, or disbeliefs, significantly alter results.

Because of this, good studies must be double-blinded. Neither the patient nor the doctor knows which medicine is real, and which is fake.

Palafox and his colleagues designed such a study. Their double-blind trial included 42 patients from five hospitals in three Pacific island nations from 1992 to 1995. By random choice, some patients received mannitol, some sugar water, both intravenously.

Even after the study was over, however, the answer was still unclear. The statistics had to be impartially analyzed.

Finally, years after his first observation that mannitol relieved some of the symptoms of ciguatera fish poisoning, Palafox has some firm data. The study, soon to be published, (no details available yet) shows that yes indeed, mannitol helps ease the misery of some ciguatera symptoms.

A key word here is some. The medicine doesn't relieve all of ciguatera's many ills, nor is it a cure for the actual poisoning. The good news, however, is that even six or more days after the initial poisoning, mannitol still helps.

Mannitol, used in the past mostly to rid the body of excess water, has been around a long time. No one knows why or how this medication works on ciguatera symptoms, which is one reason the medical community has been reluctant to adopt or endorse this treatment.

Even though Palafox's new study does not answer these questions, it does show mannitol helps. Its use in ciguatera poisoning should increase.

Ciguatera fish poisoning exists in oceans between 35 degrees north and south of the equator. (The Hawaiian Islands lie within that range at about 19 through 29 degrees north.)

The poisoning originates from a tiny dinoflagellate that small, grazing fish eat. Larger fish eat these grazers and pass the poison up the food chain to humans.

Ciguatoxic fish look and taste normal. Neither cooking, freezing nor drying deactivates this toxin.

About 90 percent of people who eat affected fish get sick 15 minutes to 12 hours later. Since the toxin affects nerves, symptoms are numerous and widespread. In Palafox's study, mannitol relieved approximately 75 percent of these symptoms.

One wicked aspect of ciguatera poisoning is its duration. The acute illness can last up to six weeks, with mild but annoying symptoms lingering for years.

The best way to avoid ciguatera poisoning is to avoid eating reef fish.

If you do get sick, however, go to an emergency room, even if it's days later. You'll likely be treated with mannitol.



Susan Scott is a marine science writer and author of three books about Hawaii's environment. Her Ocean Watch column appears Monday in the Star-Bulletin.



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