Tramadol is a synthetic opioid-like drug used as a painkiller. The pills were stashed in three containers at the port of Genoa, labelled as blankets and shampoo and set to be loaded on a cargo ship bound for Misrata and Tobruk in Libya, The Times reported.
"ISIS is making a fortune from this traffic, giving it to its fighters to make them feel no pain," the British newspaper quoted an Italian investigator as saying.
The Italian police said the consignment had come from India and would have been used for two purposes -- to help finance terrorism and for use by terrorists as a stimulant and to heighten resistance to physical stress, the BBC reported.
Boko Haram, the Nigerian terror group, is said to feed child soldiers dates stuffed with tramadol before sending them on missions.
ISIS is already known for feeding its fighters Captagon, an amphetamine that blocks hunger, fear and fatigue.
The tramadol pills would sell for two dollars each in Libya, said the investigator.
Last year, police at the Greek port of Piraeus found a container carrying 26 million tramadol tablets, originally from India and allegedly destined for a Libyan company with ties to ISIS, the report said.