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Management of Adverse Effects of Morphine Guidelines for Healthcare Professionals Professor Ramani Vijayan, Department of Anaesthesiology, UMMC. From her notes for participants of Palliative Care Conference, 26 - 27 April 2003 at Monash University Malaysia. (Edited) Some of the more common adverse effects of morphine are:
Nausea/Vomiting 30% of patients may have nausea and/or vomiting at the start of morphine therapy. Anti-emetics, such as metochlopramide 10mg three times a day, should be prescribed when needed.
Maintain sedation scores. If patient becomes too drowsy, you can either omit the next one or two doses of morphine or restart morphine at 50% of the previous dose when the patient wakes up and begins to feel uncomfortable.
Mild cognitive impairment can occur at the start of opioid therapy, particularly in older patients. Similar to sedation, this effect is usually transientl If confusion occurs, omit the next one or two doses and restart at 50% of the previous dose. If confusion persists, look for other causes as delirium may be multifactorial. Common causes are hypercalcaemia, hypoxia, sepsis or neoplastic involvement of the central nervous system. A small dose of oral haloperidol, 0.5 - 1mg twice a day, may be useful if there are no other reasons for the confusion.
If the patient cannot pass urine, you may have to do an in-out bladder catheterisation. Alternatively, naloxone 0.1mg intravenously may be tried. At this dose, the analgesic effect of morphine is not reversed and catheterisation may be avoided. Sedation, nausea/vomiting, confusion and urinary retention may occur at the start of morphine therapy and they do not usually pose major problems with continued use.
This is usually a major problem and should be actively prevented. Dehydration, inadequate food intake and inactivity contributes to constipation. Laxatives are almost always necessary and should be routinely prescribed unless contraindicated, such as diaorrhoea, ileostomy, intestinal obstruction. Attention to diet and exercise, where appropriate to the situation, is important. Combination therapy includes
Clinically important respiratory depression is rare when the dose of morphine is titrated against a patient's pain. Pain acts as a physiological antagonist to the central depressant effects of morphine. When morphine is used by the oral route, sedation always comes before respiratory depression. Monitoring of sedation is therefore important.
Tolerance (when requirement for morphine increases) develops only in 5% of patients with cancer pain. The more important reason for dose escalation is extension of the disease.
Addiction is a term used for the compulsive use of a drug for its psychic effects. Addiction is NOT a problem in patients with pain and this should not be a reason to withhold adequate or increasing doses of morphine. The commonest reason for frequent requests for analgesia is inadequate analgesia, not drug seeking behaviour. Pain control should therefore be a priority. However, physical dependence to morphine may occur with long term use and this should not be interpreted as addiction.
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