Pressure is mounting in the United States for tighter curbs on access to the anaesthetic propofol, amid fears that a growing number of healthcare professionals are becoming addicted to it.

The drug has been implicated in the death of singer Michael Jackson, who died in June, after the Los Angeles coroner’s office said that “lethal levels” had been found in the singer’s body. Propofol, which has been licensed for use since 1986, is given intravenously to induce brief anaesthesia and is not generally available outside hospitals and clinics.

In July the American Association of Nurse Anesthetists warned that “abuse of …