Morphine and Opioid Side Effects





Certain side effects are common to all opioids. These are readily managed by appropriate dosing and concomitant use of other agents such as laxatives and anti-emetics. True allergic reactions are rare.

ConstipationMust be anticipated and prevented in all patients on weak or strong opioids. Constipation may be less severe

in some patients with transdermal fentanyl. Regular stimulant laxatives must be commenced at the same time as weak or strong opioids. The dose of laxative required may increase as the dose of opioid increases. (See Constipation)

Sedation – May occur with the first few doses, but then lessens.

Nausea – Is a common problem (for around 30%) during the first few days of treatment.  If it occurs haloperidol, domperidone, cyclizine, or metoclopramide are suitable anti-emetics. (See Nausea and Vomiting).

 Also recognised are: Dry mouth, itching, sweating, hallucinations and myoclonic jerks.

Psychological Addiction – Is rare in patients taking opioids for their analgesic effects.

Tolerance (i.e. to the analgesic effects) – May occasionally occur, but an increase in dose requirement often reflects an increase in pain due to advancing disease. For patients who exhibit tolerance to a particular strong opioid, switching to another strong opioid might be helpful. Seek specialist palliative care advice.

Respiratory Depression – Is not a risk when doses are increased
by appropriate increments and the patient is reviewed accordingly. Pain is a physiological antagonist to the central depressant
effects of opioids. If pain is relieved by alternative methods e.g. radiotherapy or nerve block, a reduction in opioid dose will be required.
If side effect profile remains too troublesome, a switch to an alternative second line opioid should be considered. Seek specialist palliative care advice.