Opioids remain a mainstay of treatment for chronic and surgical pain, despite their side effects and risk for addiction and overdose.

While conventional local anesthetics block pain very effectively, they wear off quickly and can affect the heart and brain.

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.

(Tetrodotoxin is notorious for causing fugu poisoning from improperly prepared sashimi.)

"A lesson we learned is that with our previous delivery systems, the drug can leak out too quickly, leading to systemic toxicity," says Kohane.

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