Opioid adverse effects in palliative care

There is wide interindividual variability in the adverse effects experienced by patients who take an opioid.

Reduce the impact and incidence of opioid adverse effects by:

using the same opioid for regular and intermittent therapy (if feasible)
individualising the choice and dose of opioid
slowly increasing the opioid dose to effect, especially when starting or changing therapy
informing patients and their carers about potential adverse effects and how they are monitored, prevented and addressed.

Management of opioid adverse effects involves thoroughly assessing (and investigating when indicated) symptoms attributed to an opioid, and considering other causes (eg confusion or sedation may indicate delirium caused by hypercalcaemia, infection or the dying process). In general, for patients who experience opioid adverse effects and whose symptoms are adequately managed, consider reducing the dose of the opioid. If adverse effects persist or symptoms are inadequately controlled, switching opioids may be an option.

Management strategies for frequently seen adverse effects of opioids used in palliative care lists some frequently seen adverse effects of opioids and strategies for prevention or management in palliative care. The Pain and Analgesia guidelines provide more extensive advice on opioid adverse effects, including neuroadaptive and physiological changes (eg opioid tolerance, physical dependence, opioid-induced hyperalgesia), and adverse effects associated with short-term use and long-term use.

Table 1. Management strategies for frequently seen adverse effects of opioids used in palliative care
Adverse effect	Management strategy	Features of adverse effect
Nausea	Consider antiemetic therapy for a few days and then review (see Nausea and vomiting in palliative care). For persistent nausea despite antiemetic therapy, consider switching opioids or route of administration.	Usually occurs when starting an opioid and subsides within 1 to 2 weeks.
Constipation	Encourage adequate fluid intake and mobility, if possible. Always consider a regular laxative with opioid therapy; see Opioid-induced constipation in palliative care for further information on prevention and management.	–
Sedation	If sedation is excessive, reduce opioid dose by 25 to 50% and monitor closely for a decrease in respiratory rate; sedation may indicate opioid-induced ventilatory impairment. For persistent sedation, switch opioids.	Tolerance usually develops rapidly. Sedating effect is additive when an opioid is given with other sedating drugs (eg benzodiazepines).
Cognitive impairment	Patients need to monitor their own reactions to opioids and avoid driving or operating machinery until treatment is stable; see also Fitness to drive in palliative care.	More common when starting therapy or after a dose increase of more than 20%.
Hallucinations and delirium	Exclude other potentially reversible causes of hallucinations and delirium. If an opioid is thought to be a contributing factor, consider reviewing the dose or switching opioids. See Delirium in palliative care for prevention and management of delirium.	–
Rigidity and myoclonus	See Opioid-induced myoclonus in palliative care for management.	More common with high doses of opioids or in kidney impairment (due to accumulation of neurotoxic metabolites) but can be idiosyncratic.
Itch	See Opioid-induced itch in palliative care for management.	–
Dry mouth	See Dry mouth in palliative care for management.	When opioids are appropriately titrated to symptoms they rarely cause ventilatory impairment. For management of opioid-induced ventilatory impairment, see Opioid-induced ventilatory impairment in palliative care.

When opioids are appropriately titrated to symptoms they rarely cause ventilatory impairment. For management of opioid-induced ventilatory impairment, see Opioid-induced ventilatory impairment in palliative care.