Pfizer Inc. has been socked with an eye-popping $141 million penalty for unlawfully promoting its epilepsy drug Neurontin for unapproved uses for which, the plaintiffs said, it didn’t even work.

A federal jury in Boston on Thursday concluded that the pharmaceutical giant had violated federal racketeering laws in promoting the drug for so-called off-label uses that were ineffective. The jury’s verdict was actually $47 million, but the penalty was automatically tripled under the federal Racketeer Influenced and Corrupt Organizations Act.