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Opioid analgesia
There is a huge range of opioid analgesics available for use in cancer pain management, most working in slightly different ways (figure 1).
Figure 1 Opioid analgesics
Opioid analgesics can lead to physical and psychological dependence and tolerance.
Dependenceis characterised by withdrawal symptoms if the drug is withdrawn abruptly, or if an antagonist is administered.
Tolerance is characterised by decreased efficacy and duration of action with prolonged repeated use of the drug (leading to the need for higher doses to maintain the same level of analgesia).
These are a normal pharmacological response to the use of these drugs, and does not normally prevent their safe use in cancer pain management. Patients with stable pain often remain on the same dose for many weeks.
Psychological dependenceis characterised by craving for the drug and a preoccupation with obtaining it. Wide clinical experience has shown that psychological dependencerarely occurs in cancer patients taking opioids for pain relief.