Opium and its many preparations have been used for the treatment of pain for over 2000 years. Many of its pharmacological effects, such as euphoria and sedation, appear to have been known as far back as at least 3000 bc, at the time of the ancient Sumerians and Minoans, and mention is made of its analgesic effect in Egyptian mythology (Benedetti and Premuda, 1990). However, while its use has continued over the years, and while it was prescribed by physicians such as Hippocrates for a variety of ailments, the first accepted written reference to its analgesic properties is said to be found in the third century bc writings of Theophrastus (a pupil of Aristotle), who also described its lethal effects (Benedetti and Premuda, 1990).