Counterfeit Norco contains promethazine, say researchers

A drug that is used by addicts to boost the effects of opioid drugs has been found in counterfeit versions of the Actavis' painkiller Norco.

A report published in the US Centers for Disease Control and Prevention (CDC) Morbidity and Mortality Weekly Report describes several cases in the San Francisco earlier this year in which the fake Norco caused serious ill effects resulting in hospitalisations.

Investigations into the tablets subsequently revealed they contained not hydrocodone and acetaminophen - the active ingredients in genuine Norco pills - but a much stronger opioid called fentanyl and also promethazine, a drug usually used to treat nausea, vomiting and motion sickness. In some cases traces of cocaine were also found in some samples.

Promethazine has not been reported as an additive in previous counterfeit or adulterated fentanyl-containing products, according to the CDC. The drug is understood to be common among chronic opioid users and is thought to potentiate the 'high' from opioids, said the agency.

"The US is experiencing an opioid epidemic with synthetic opioids such as fentanyl responsible for the highest rise in death rates in recent years," says the paper, which is authored by researchers from the University of California, San Francisco (UCSF).

"The distribution of counterfeit tablets represents a major public health threat given the potentially lethal nature of the tablets," they add.

No information has been released regarding the source of the counterfeit tablets, and an investigation is ongoing.

Intoxications with fake Norco tablets - which like the genuine product and the pills studied in the CDC report have 'M367' stamped on them - resulted in a number of fatalities in April.