Morphine, the main alkaloid of opium, was first obtained from poppy seeds in 1805.1 It is a potent analgesic, though its use is limited due to tolerance, withdrawal, and the risk of abuse.2 Morphine is still routinely used today, though there are a number of semi-synthetic opioids of varying strength such as codeine, fentanyl, methadone, hydrocodone, hydromorphone, meperidine, and oxycodone.
Morphine was the first, and in many ways, the most important opioid used to treat acute and cancer pain. However, morphine is a short-acting medication, and the frequency of administration necessary to maintain adequate blood levels made it difficult to use this agent in the chronic setting. It was not until morphine was available in a long-acting formulation that it became used for chronic, noncancer pain. With once or twice a day dosing, steady-state blood levels can be achieved, compliance can be improved, and patients can sleep through the night. There should also, theoretically, be less reinforcement of drug misuse behavior, although that has never been proven.