1.     Acute pain: opioids are often used to treat pain due to trauma, operations, kidney stones etc.

2.     Chronic pain: both cancer-related and "non-malignant chronic pain".

Limitations to use relate to the type of pain being treated: some types of pain are regarded as "opioid resistant" or even "opioid insensitive".

Visceral pain is regarded as relatively opioid resistant as is neuropathic pain (originating in nerves) but both these problems may be adequately addressed with careful titration of the opiate dose to a sufficient level.

Central pain tends to be more or less opioid insensitive.

These problems may be tackled by using adjunctive therapy, such as with antidepressants or anticonvulsants etc. (These types of medication will be the subject of future articles.)