The Pharmaceutical Journal
Vol 278 No 7457 p745-748
23 June 2007

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Opioid analgesics in palliative care

In a second article on the treatment of pain in palliative care, Andrew Dickman discusses the use of opioids

Continuing professional development articles

Palliative care series

SUMMARY

The discovery of the opioid receptors began in the 1970s and three (µ, d and k) are now recognised. Most current opioid analgesics interact preferentially with µ receptors, although some have actions at d and k receptors. The revelation that opioid receptors are present on peripheral sensory neurones and immune system cells, has led to the realisation that the opioid system is involved in a host of actions, including the central and peripheral modulation of pain transmission and the regulation of immune and neuroendocrine processes.

Opioid pharmacology has become even more complex with the recent suggestion of multiple receptor subtypes (eg, µ₁ and µ₂). The predominant subtype can have a profound effect on analgesic response. In addition, the existence of subtypes may partially explain incomplete cross-tolerance to µ receptor opioids and the need to reduce the equianalgesic dose by 25–30 per cent when switching between them.

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