Oral and parenteral opioids

Rescue medication is taken as required, rather than on a regular basis. Oral opioids have a defined role in the management of breakthrough pain, but will only be effective if it is an opioid-responsive pain. Although the oral route is generally effective in the management of background pain, it is often less effective in the management of breakthrough pain. The ‘correct’ dose of rescue medication is the dose that provides maximal analgesia with minimal side effects. The pharmacokinetic profile of many orally delivered drugs does not mirror the temporal characteristics of many breakthrough pain episodes. The rectal administration of opioids is well established, although is now uncommon in day-to-day clinical practice. The intravenous route of administration is primarily used in secondary care settings. Intravenous/subcutaneous opioids provide rapid onset of analgesia, but are generally not practical in outpatient settings.