Quaalude, also known by its generic name methaqualone, is a sedative-hypnotic drug that was widely prescribed in the 1960s and 1970s for its calming effects and to treat insomnia. It gained popularity as a recreational drug due to its euphoric effects but was eventually banned in many countries due to concerns over abuse and addiction. The drug's sedative properties can lead to respiratory depression and overdose, making it dangerous when misused.