The AFL chief executive said the league wants to restrict injections to painkillers only.
"Of course I'm concerned ... if it (the report) was accurate, and I suspect part of that has some accuracy," Demetriou said of the Herald Sun story.
"I expressed concern at the time, I expressed concern as a parent."
Essendon are under three investigations after going to the AFL last month and revealing concerns about supplements given to their players last year.
Wednesday's newspaper report said some Bombers received up to 40 needles at an anti-ageing clinic across the road from their Windy Hill headquarters.
The report also said police witnessed some Essendon players arriving at and leaving the clinic.
The Essendon investigation and the Australian Crime Commission investigation have prompted the AFL to tighten their integrity operations.
"We announced recently as a part of the sweeping changes that we are going to reduce the incidence and use of injections and confine it to painkillers only," Demetriou said.
"We've taken very swift action and the days of injections and the days of intravenous use are gone."