AH-7921: the list of new psychoactive opioids is expanded

AH-7921 is a structurally unique synthetic opioid analgesic that has recently entered the drug arena in Europe, the USA, and Japan. Although it was synthesized and patented in the mid-1970s, it was first identified in a seized sample purchased via the Internet in July 2012 and formally brought to the attention of the European Union early warning system in August 2012 by the United Kingdom. Several in vitro experiments and animal model studies established the morphine-like analgesic action of AH-7921 as a μ-opioid receptor agonist that has been found to be several times more potent than codeine and at least as potent as morphine. This novel psychoactive substance has already led to eight non-fatal intoxications and 16 deaths in Sweden, the United Kingdom, Norway, and the USA. Thus, AH-7921 is a current public health risk, and better international collaboration, effective legislation and continuous community alertness are needed to tackle this current growing problem. The aim of this review is to summarize the current knowledge about this drug concerning its chemistry, pharmacology, and toxicology, as well as its international legal status. The limited existing analytical methodologies for the determination of AH-7921 in biological samples are also presented. Published or reported AH-7921-related cases, fatalities, or intoxications, and self reports from drug users are reviewed.