There are many sources of opioids, including raw poppy seeds, products made from poppy seeds (eg, poppy seed tea or kits for smoking), semisynthetic drugs (eg, heroin, morphine, and oxycodone), and synthetic drugs (eg, methadone and fentanyl). Over the centuries, opioids have been used as surgical analgesics, to stop diarrhoea and prevent tooth decay, as an adjuvant treatment of insomnia, to treat cancer and chronic pain, and as a recreational drug.

The opioid-abuse epidemic is a major problem in public health worldwide. In this special issue, researchers from the Americas present their views on the opioid crisis in Brazil, Mexico, and the USA. Although it is difficult to establish the major drivers of this crisis, experts point toward the influence by pharmaceutical companies, inadequate regulation, overprescribing by the medical profession, and increased use of illegal heroin and synthetic opioids. An explanation for the prevalent use or misuse of this class of drugs is their highly addictive power....