[Breakthrough pain and short-acting opioids]

Conventional opioid therapy consists of the regular administration of extended-release opioids following fixed time intervals and, as needed, the supplemental use of an immediate-release formulation. For the patient needs of such rescue medication, recent studies distinguished different scenarios, such as an inadequate daily opioid dose or time interval (end-of-dose failure) from so-called breakthrough pain where the attacks can suddenly occur either spontaneously (idiopathic pain) or due to certain provocations (incident pain) despite optimal dose adjustment. In line with this time course, a fast and short-lasting elevation of the opioid plasma concentration seems to be reasonable. Although in a recent European survey breakthrough pain attacks in the majority of cancer pain patients were sufficiently treated with immediate-release opioids, currently running clinical trials examine whether the application of transmucosal or intranasal fentanyl with their known reduced time to maximum plasma concentrations show a possible advantage in comparison to immediate-release opioids. In these clinical trials the pain intensity and number of pain episodes were significantly reduced following transmucosal or intranasal fentanyl; however, the magnitude of these effects does not convincingly appear to be clinically relevant. Among other reasons this may be related to the fact that those patients who would perhaps benefit from such treatment have not yet been identified.