Wilson and Gisvold, pgs. Opioid anagesics are well known for their ability to reduce the perception of pain without a loss of consciousness . The original opioids were derived from opium , which is a partially dried latex harvested fromt the opium poppy, papaver somniferum .
Opium contains morphine, codeine, noscapine, papaverine, and thebaine.
Thebaine is a convulsant drug that produces no analgesia, and as such it is not used clinically. However, it is an important synthetic intermediate in the production of semisynthetic opioids. Morphine itself, which was discovered in 1809, has a variety of effects, among which are an increase in the tolerance to pain, somnolence, euphoria, an antitussive effect, respiratory depression, constipation and emesis . In addition, morphine has a high addiction liability . Derivatives of morphine have been sought that retain the anagesic activity of the parent, but that have improved oral bioavailability and a reduction in addiction liability and other deleterious side effects .