Opioids are the mainstay of treatment for moderate to severe
cancer pain. In recent years there have been many advances in the use of
opioids for
cancer pain. Availability and consumption of
opioids have increased and
opioids other than
morphine (including
methadone,
fentanyl,
oxycodone) have become more widely used. Inter-individual variation in response to
opioids has been identified as a significant challenge in the management of
cancer pain. Many studies have been published demonstrating the benefits of
opioid switching as a clinical maneuver to improve tolerability.
Constipation has been recognized as a significant burden in
cancer patients on
opioids. Peripherally restricted
opioid antagonists have been developed for the prevention and management of
opioid induced constipation. The phenomenon of
breakthrough pain has been characterized and novel modes of
opioid administration (transmucosal, intranasal, sublingual) have been explored to facilitate improved management of breakthrough
cancer pain. Advances have also been made in the realm of molecular biology. Pharmacogenetic studies have explored associations between clinical response to
opioids and genetic variation at
a DNA level. To date these studies have been small but future research may facilitate prospective prediction of response to individual drugs.