Which of the following is a common sleep aid?

Ambien is a common sleep aid, primarily prescribed for the treatment of insomnia. It works as a sedative that helps to initiate sleep by affecting neurotransmitters in the brain, promoting relaxation and drowsiness. This medication is specifically designed to assist with sleep issues rather than other health concerns.

While Xanax may have sedative properties and can be used to manage anxiety, it is not primarily indicated as a sleep aid. It is typically prescribed for anxiety disorders and panic disorders, making its primary function distinct from that of Ambien. Penicillin, an antibiotic, is used to treat bacterial infections and has no relation to sleep or its disorders. Similarly, Colace is a stool softener, and its purpose is to alleviate constipation rather than influence sleep patterns. Therefore, Ambien stands out as a dedicated sleep aid, making it the correct choice.