“Monster Trucks” won’t hit theaters for four months, but it appears to have already driven Paramount Pictures off course.

Viacom Inc.’s movie studio took the unusual step Wednesday of announcing a $115 million impairment charge “related to the expected performance of an unreleased film.” Analysts quickly zeroed in on “Monster Trucks,” a Jan. 13 release about a teenager who discovers a creature that gives his pickup special powers.

The...