MORPHINE: SIDE EFFECTS-DYSPHORIA AND PSYCHOTOMIMETIC EFFECTS, MYOCLONUS AND GASTROINTESTINAL
Psychotomimetic or dysphoric side effects may occur with morphine or other opioid drugs and most frequently manifest as apprehension, confusion, hallucinations or nightmares. If necessary, treatment with a tranquillizer (e.g. haloperidol) may be beneficial; if severe, changing to an alternative opioid should be considered. Psychotomimetic side effects occur in less than
1-2% of patients on morphine but are reported in up to 10% of patients taking pentazocine.
Myoclonus-Multifocal myoclonus occurs occasionally in patients on morphine, usually those receiving higher doses. If troublesome, treatment is by reducing the dose (if feasible), adding a benzodiazepine such as clonazepam, or changing to an alternative opioid.
Gastrointestinal-Nausea and vomiting. Nausea occurs frequently when therapy with morphine is commenced; vomiting is less common. The nausea is usually mild and subsides after a few days. It is due to a direct effect on the chemoreceptor trigger zone in the medulla, compounded by any morphine-related gastric stasis and constipation. Patients must be warned of the possibility of nausea for a few days after starting therapy and given a supply of antiemetics to take if need be. Prophylactic antiemetics should be given if there is a history of nausea and vomiting with previous opioid therapy or if other potential causes of nausea and vomiting are present.
Constipation-Morphine reduces gastrointestinal secretions and motility, leading to delayed gastric emptying and constipation. Constipation will occur in all patients taking morphine regularly, with the exception of those with an ileostomy or diarrhoea secondary to malabsorption.

• Every patient commencing therapy with morphine requires dietary advice and the prescription of laxatives to prevent constipation.
• Tolerance does not develop to the constipating effects of morphine and dietary and laxative therapy are necessary for the duration of treatment.

Xerostomia-A significant proportion of patients on chronic morphine therapy complain of dryness of the mouth. Treatment is symptomatic. If severe, an assessment for other causes should be made, especially drugs with anticholinergic side effects such as antidepressants.
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Pain Relief/Muscle Relaxers