Horizant (gabapentin enacarbil) is a prescription medicine used to treat adults with restless legs syndrome (RLS) and nerve pain (postherpetic neuralgia) caused by shingles or herpes virus. Horizant is converted by the body into gabapentin, which works by affecting chemicals and nerves involved in pain. The exact way gabapentin works for RLS and nerve pain is unknown, but it may block certain nerve signals that contribute to pain and discomfort.