As insomnia is experienced by people who have problems to sleep, so drugs for insomnia are supposed to make the patients sleep. But, paradoxically, Ativan and Ambien – both are sedative drugs used for treating insomnia – are actually waking up people from comma. Some coma patients are being awoken by Ativan and Ambien.
The first report of a zolpidem [aka Ambien] awakening came from South Africa, in 1999. A patient named Louis Viljoen, who, three years before, was declared vegetative after he was hit by a truck, had taken to clawing at his mattress during the night. Thinking he was suffering from insomnia, his family doctor suggested zolpidem to help him sleep. But 20 minutes after his mother ground the tablet up and fed it to him through a straw, Viljoen began to stir. His eyes, which normally wandered the room, vacant and unfocused, flickered with the light of consciousness. And then he began to talk (his first words were "Hello, Mummy"), and move (he could control his limbs and facial muscles). A few hours later he became unresponsive. But the next day, and for many days after that, zolpidem revived him, a few hours at a time.
Here was a case worthy of Hollywood: three years was well past the point at which doctors would expect any sort of spontaneous recovery. Viljoen awoke with the ability to speak in complete sentences. Not only did he recognize his mother, but he also recognized the voices of people who had spoken to him only when he was apparently vegetative. He remembered nothing of the mysterious realm he kept receding back into. When doctors asked him what it was like to slip away, he said he felt no changes at all. But he could recall conversations from the previous day's awakening, along with bits and pieces of his former life: his favorite rugby team, specific matches he attended, players that he rooted for and against. As time passed, his cognition improved. He could laugh at jokes, and his awakenings stretched from a few hours to entire days. Eventually, he no longer needed zolpidem.
Source: NYTimes