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.

Constipation

Must 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).

Nausea

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

Psychological Addiction

Is rare in patients taking opioids for their analgesic effects.

Tolerance (i.e. to the analgesic effects)

May 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 rarely 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.

Other recognised side effects are:

• Dry mouth
• Itching
• Sweating
• Hallucinations
• Myoclonic jerks

The latter two are part of a multifactorial syndrome known as neurotoxicity.

Neurotoxicity

Causes a spectrum of symptoms, from mild confusion or drowsiness to hallucinations, delirium, and seizures.

Seek Specialist advice if opioid induced.

Sedation

May occur with the first few doses, but then can lessen. Caution this may impair fitness to drive, medical advice is advised regarding this if appropriate. Psychostimulant medications can be prescribed to help with this, seek specialist advice.

Myoclonus

Twitching or clonic spasm of a muscle or group of muscles. It can be seen in any muscle group/limbs, may vary in severity and can be sporadic or continuous. Consider reducing opioid dose and add an adjuvant or switch to different opioid and consider reduce dose of new opioid by 20-30%.

Hallucinations (usually visual)

Reduce opioid dose and add an adjuvant or switch to different opioid and consider reduce dose of new opioid by 20-30%, treat symptomatically with Haloperidol.

Delirium

Confusion / Agitation/ Cognitive impairment

Treat symptomatically with Haloperidol/Levomepromazine or newer atypical anti-psychotic in the short term. Consider reducing opioid dose and add an adjuvant (preferably non-psychoactive adjuvant) or switch to different opioid and consider reduce dose of new opioid by 20-30%.

Hyperalgesia / Allodynia:

• An excessive sensitivity to pain (usually that is already present).
• Allodynia: Ordinary painless (non-noxious) stimulus/sensation is experienced as being painful.

Consider reducing opioid dose and add an adjuvant or switch to different opioid and consider reduce dose of new opioid by 20-30%.

If side-effect profile remains too troublesome, a switch to an alternative second line opioid should be considered.
Seek specialist palliative care advice.