Alternatives to opioids for treating pain are sorely needed. A study in rats suggests that tetrodotoxin, properly packaged, offers a potentially safe pain block.

In tiny amounts, in a slow-release formulation that efficiently penetrates nerves, the toxin provided a safe, highly targeted, long-lived nerve block, researchers report today in Nature Communications. The study was led by Daniel Kohane, MD, PhD, director of the Laboratory for Biomaterials and Drug Delivery at Boston Children’s Hospital.

Kohane has long been interested in neurotoxins found in marine organisms like pufferfish and algae. In small amounts, they can potentially provide potent pain relief, blocking the sodium channels that conduct pain messages. Kohane’s lab has experimented with various ways of packaging and delivering these compounds in tiny particles, activating local drug release with ultrasound and near-infrared light, for example.

For the new study, the team chose tetrodotoxin, a potent, commercially available compound derived from pufferfish. (Tetrodotoxin is notorious for causing fugu poisoning from improperly prepared sashimi.)

Taming a lethal toxin

Rather than load tetrodotoxin into particles as before, the team bound it chemically to a polymer «backbone.» The body very slowly degrades the bond between tetrodotoxin and the polymer via hydrolysis, the natural breaking of chemical bonds by water). This releases the drug at a slow, safe rate.

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Materials provided by Boston Children’s Hospital. Note: Content may be edited for style and length.