Current guidelines on the treatment of moderate to severe
cancer pain recommend the use of scheduled doses of
opioids for persistent
pain combined with "as needed" doses of similar agents for
breakthrough pain. Oral drugs given on an "as needed" basis can be problematic for patients with difficulty in swallowing or for those who suffer from
nausea and
vomiting. Further,
breakthrough pain can become excruciating in a relatively short time, a drawback for
analgesics that require gastrointestinal (GI) absorption before
pain relief can begin. Hence, there is considerable interest in the development of novel
drug administration routes to provide rapid relief of
breakthrough pain, particularly through a route that bypasses the GI system. Sublingually administered
morphine has sometimes been used in the treatment of
breakthrough pain because some believe it provides effective
analgesia via an appropriate alternate route. Available pharmacological data, however, do not consistently support the rapid absorption of
morphine through the sublingual mucosa, and clinical data concerning the efficacy of sublingual
morphine for the treatment of
cancer pain are limited, not well-controlled, and inconclusive. While there seems to be a need for provision of rapid, effective
analgesia to
cancer patients by an alternative route, sublingual
morphine may not satisfy this requirement. Newer formulations of
analgesics should be tested in the treatment of
breakthrough pain due to
cancer.