The double effect of pain medication: separating myth from reality.

The principle of double effect is used to justify the administration of medication to relieve pain even though it may lead to the unintended, although foreseen, consequence of hastening death by causing respiratory depression. Although a review of the medical literature reveals that the risk of respiratory depression from opioid analgesic is more myth than fact and that there is little evidence that the use of medication to control pain hastens death, the belief in the double effect of pain medication remains widespread. Applying the principle of double effect to end-of-life issues perpetuates this myth and results in the undertreatment of physical suffering at the end of life. The concept of double effect of opioids also has been used in support of legalization of physician-assisted suicide and euthanasia.