Barbiturates are organic compounds derived from barbituric acid. They are used to treat to use and prevent convulsions and anxiety in addition to being used as a sleep aid. Common side effects are drowsiness, respiratory depression, hypotension and decreased body temperature. They are scheduled drugs — some are schedule III, which means that they have a high risk of abuse but are useful therapeutically, whilst others are schedule IV, which means that they have a strong tendency toward dependence but are used in therapy.