ABSTRACT
Nearly everyone will have an experience with severe pain at some point in their lives. Acute pain associated with trauma, burns, surgery, infection (e.g. dental abscess), or certain types of chronic pain (e.g. that associated with advanced cancer) are usually treated with some form of opioid drugs. While opioid drugs have potent cough suppressant and antidiarrheal activity, their primary use is for the treatment of pain and induction of surgical anesthesia. These drugs are, for the most part, highly effective for the relief of pain but their clinical use is restricted for many reasons. These reasons range from the relatively minor problems of nausea, sedation and constipation caused by most opioid drugs to the much more serious problems of respiratory depression, physical dependence, and addiction that are linked to the more potent opioids (Duthie and Nimmo, 1987).
