Opiates can also cause delirium but they remain a vital class of drug for treating pain. It is important to remember that pain in itself can precipitate delirium.
A systematic review cited an OR of delirium associated with treatment with opioids of 2.5 (95% CI 1.2 to 5.2).81 However, the main opioid in the review, which carries the highest risk, is pethidine (OR 2.7, 95% CI 1.3 to 5.5), which is anticholinergic and rarely used in the UK. More commonly used opioids such as morphine (OR of delirium 1.2, 95% CI 0.6 to 2.4) and fentanyl (OR of delirium 1.5, 95% CI 0.6 to 4.2) were not significantly associated with delirium.81
The opioid with the lowest odds of causing delirium was oxycodone but this still had a confidence interval that crossed 1 (OR 0.7, 95% CI 0.3 to 1.6).81
When using opiate analgesia titrate to the minimal effective dose to achieve pain control and minimise side effects.
If opiates are used laxatives should be prescribed to prevent constipation which can contribute to delirium.