Opioid painkillers are some of the strongest analgesic medicines, but they are also the riskiest owing to a range of side effects, including addiction. An experimental opioid painkiller designed to be reversibly switched on and off with different light frequencies, keeping its action local and out of the brain, may eliminate the dangerous side effects of current opioids, according to a study led by Weill Cornell Medicine and University of Pennsylvania investigators. The findings herald a broad new approach for targeting medicines more precisely and effectively.

Vaccine safety experts say more research into the side effects would be welcome yet question whether the health secretary’s effort will be grounded in science.

Voters in more than 20 states will be faced this year with new laws for registering to vote and casting ballots.

Media witnesses say Tennessee officials were unable to carry out the execution of Christa Gail Pike for a 1995 murder on Wednesday.