(NYT) – New research shows that tolerance has become so strong that common treatments for opioid addiction are no longer effective for many patients.

Habitual users of fentanyl have developed such a strong tolerance to the drug that standard doses of medications to manage withdrawal and initiate recovery are no longer working for many patients, a team of researchers in Los Angeles has found.

Their study, published in the journal Drug and Alcohol Dependence, presents a picture of the dangerous volatility of the city’s street supply and the capacity of users to tolerate ever greater amounts of pure fentanyl, which is at least 50 times more potent than heroin. (Read More)