• Adverse effects are less serious when morphine is used to relieve the symptoms of dyspnoea than when it is used for analgesia, because the doses used for symptom relief of dyspnoea are generally lower.
• Drowsiness occurs commonly at the start of treatment or after dose increases. People should be warned to avoid activities in which drowsiness may be detrimental. Most people develop tolerance to drowsiness within a few days. Persistent sedation may be resolved by dose reduction or an opioid switch.
• Constipation is a common ongoing problem, because tolerance to this adverse effect does not develop with morphine use:
• When using an opioid cough suppressant, co-prescribe a regular stimulant laxative (e.g. senna or bisacodyl) with a faecal softener (e.g. docusate or lactulose), or a laxative likely to have both properties (e.g. co-danthramer or co-danthrusate) to prevent opioid-induced constipation. Note: people taking dantron-containing laxatives may experience reddening of the perianal area.
• Other common adverse effects of morphine (especially in elderly people) include nausea, vomiting, and unsteadiness:
• An anti-emetic (e.g. haloperidol or metoclopramide) should be prescribed [Twycross et al, 2002]:
• Regularly for the first week to prevent opioid-induced nausea and vomiting if the person has experienced nausea with a weak opioid, or
• On standby, for use on an 'as required' basis for a week, in case the person experiences nausea with morphine but has not previously had nausea with a weak opioid.
• Other adverse effects of strong opioids include dry mouth, sweating, pruritus, hallucinations, myoclonus, and bronchoconstriction.
• Note: respiratory depression from opioids is rare, and these agents do not hasten death if appropriately titrated [Fraser Health, 2006].

[Twycross et al, 2002; BNF 53, 2007]