heroin

Another class of drugs that exploit a natural mechanism to decrease the ability of CaV2.2 to respond to pain signalling are the opioid drugs, like morphine and heroin.

Indeed some critics have pointed to the DEA's crackdown on opioid "pill mills" with pushing more people to use street heroin and eventually fentanyl, which resulted in overdoses soaring as prescriptions fell.

Kennedy, who was addicted to heroin for 14 years in his youth, has also talked about wanting to help tackle America's substance abuse crisis.

Although 24 states have legalized cannabis, it remains illegal at the federal level, carrying the same criminal penalties as heroin and MDMA.

Asked about his mother's heroin addiction, the actor said it "caught her" as well as his uncle and father.