Side Effect (2008)

Lauren is an overachieving teenage babysitter for the Allens, who leave her in charge of their adorable young children, while they head out for some much-needed alone time. Unbeknownst to them, Lauren, overworked and overstressed, is getting a little extra help from a new prescription medication. The meds come on strong, twisting Lauren's appearance and causing an icy change in her demeanor, but the powerful medication also helps her get all of her duties done in a quick and efficient manner. Everything seems normal until Mr. and Mrs. Allen return home to discover the horrifying result of Lauren's brutal efficiency. Side Effect is a blood-curdling tale of science gone wrong in a pill-popping culture where the cure is more deadly than the disease.