Final answer:
Barbiturates are often taken as sleep aids due to their sedative and hypnotic effects. However, they have potential for addiction and overdose, so they have been mostly replaced by safer alternatives.
Step-by-step explanation:
A person will often take a barbiturate as a sleep aid. Barbiturates are CNS depressants and have sedative and hypnotic effects, making them effective in inducing sleep. They were originally used to replace drugs like opiates and alcohol for this purpose. However, barbiturates have potential for physical and psychological addiction as well as overdose, so they have been largely replaced by safer alternatives.