Background

Zolpidem is an imidazopyridine hypnotic agent that is approved by the US Food and Drug Administration (FDA) for the short-term treatment of insomnia in the United States. 1 It has been on the US market since 1992, sold under the trade name Ambien by the French company Sanofi-Aventis. Ambien has been widely prescribed, ranking as the ninth most prescribed medication in the United States in 2006, with more than 20 million prescriptions, 2 grossing nearly 2 billion dollars in sales3 that year alone. In 2007, Ambien’s patent protection expired, and zolpidem became available as a generic medication manufactured by 13 different companies. 4 Zolpidem remains a top prescribed medication, with more than 28 million prescriptions written in 2008, ranking as the 16th most prescribed generic medication that year, 5 with gross sales of over $700 million. 6 These figures do not include the ongoing sales for Ambien CR (controlled release), which had more than 7 million prescriptions in 2008. 7 Zolpidem is one of 13 hypnosedative medications approved by the FDA for treatment of insomnia, 8 although by far it has been the most prescribed hypnosedative over the past decade. Its popularity is the likely result of aggressive marketing9 and early reports of low rates of daytime sedation and low abuse potential. 10

However, postmarketing studies and case reports began to show that zolpidem was associated with sleep-related, complex behaviors. These included sleep driving, sleep cooking, sleep eating, sleep conversations, and, rarely, sleep sex, generally accompanied by anterograde amnesia for the event. 8 As these behaviors became recognized, the FDA requested that specific warnings be put on all hypnosedative