RCMP allege that a Nova Scotia man was high at the time of a fatal collision in Tracadie last year.
William Lionel Edmund Byron Fogarty was initially charged with two counts of dangerous operation of a motor vehicle causing death in the Nov. 24 collision.
Two teenagers from Antigonish County were killed in the two-vehicle crash on Highway 4.
Kory Mattie, the 16-year-old driver, died at the scene. His passenger, 17-year-old Nico Landry, was severely injured in the collision and died later at St. Martha's Regional Hospital.
Fogarty was driving the second vehicle involved in the crash.
RCMP said Tuesday that Fogarty is also charged with two counts of impaired driving by drugs causing death.
He remains in custody until his next court appearance on Thursday.