This is in contrast to most other classes of analgesics in use today. Fear of causing respiratory depression has often been invoked as a rationale for not using opioids to treat pain. It is now widely accepted that respiratory depression caused by opioid analgesics tends to occur largely in opioid-naive patients. It is a short-lived phenomenon that tends to be antagonized by pain. In CNCP, the risk of respiratory depression with oral dosing is extremely low and can be further minimized by careful titration of the dosage of opioids to the level of pain.
Constipation commonly accompanies opioid therapy and is usually harder to treat than to prevent.
It is, therefore, important to manage this side effect prophylactically using a stepped approach involving adequate dietary fibre, stool softeners, osmotic agents and, if necessary, regular stimulant laxative use. Nausea is a common early side effect of regular opioid therapy , and usually resolves with continued use. Antinauseants may be recommended during the initial titration phase. Sedation and cognitive deficits are also early side effects for which tolerance with continued use frequently develops once stable dosing has been achieved. There is little current evidence that the long term use of scheduled, stable dose opioid therapy leads to clinically significant cognitive or psychomotor deficits in patients with chronic pain.