Last week the U.S. Food and Drug Administration announced the approval of Horizant Extended Release Tablets (gabapentin enacarbil), a once-daily treatment for moderate to severe restless legs syndrome (RLS). The effectiveness of Horizant was studied in two 12-week clinical trials in adults. The drug may cause drowsiness and dizziness and can impair a person’s ability to drive or operate complex machinery. Horizant is the third drug approved by the FDA for the treatment of moderate to severe RLS, joining Requip (ropinirole) and Mirapex (pramipexole).