Professor Alessandro Serretti was put under investigation after 25 of his 32 students sent a letter of complaint to the university, Corriere della Sera reported.
The letter accused Serretti of giving the drugs to his students on a night out, the newspaper said. It also alleged that the professor routinely gave preferential treatment to an exclusive group of students.
Serretti has taught biology, medicine and psychology at the university since 2006.
“If even a tenth of what's been written is true it would be very serious,” Ivano Dionigi, the university's dean, told Corriere.
“I acted as soon as I learnt about it and, in view of the delicacy and the consequences of such matters, I sent the information to the correct authorities. Now I am waiting for the outcome of the magistrate's investigation,” the dean said.