- Paul Glare1
- Westmead Hospital, NSW1
1997
ExcerptMorphine is the preferred drug for the management of moderate-to-severe cancer pain. Underutilisation of morphine occurs for many reasons, including a fear - of both prescribers and patients - of side effects. Most literature on morphine for cancer pain contains statements regarding the incidence and significance of side effects reflecting expert opinion rather than being based on data; clinical information for the incidence, frequency and distress associated with these side effects is lacking. For these reasons a "snap-shot" survey was undertaken, during consultation by a palliative care physician, of side effects in chronic cancer pain in patients who had been taking morphine for at least one week, between August 1995 and January 1996.
78 patients completed the survey. They were seen in a variety of settings (hospital ward, designated palliative care unit, outpatient clinic, at home). All but two had locally advanced or metastatic cancer, and most had moderate loss of performance.
Average age was 61 years (range 37-82); 50% were males. The formulation of morphine used was MS Contin tablets 35%; immediate release solution 29%; Kapanol capsules 22% and subcutaneous injections 14%. The mean total daily dose of morphine in mg (assuming an oral:parenteral equipotency ratio of 1:2) was 232 mg (standard deviation [SD] 323 mg; range 20-1800 mg). Mean duration of treatment was 13 weeks (SD 23 weeks, range 1 week-3 years). Average pain rating was mild-moderate and average pain relief 80%, although 23% patients had troublesome incident pain. Side effects were rated by the patients from a checklist, and the commonest reported were dry mouth 86%, drowsiness 78%, constipation 72%, myoclonic jerking 68%, postural dizziness 58%, confusion 56%, nausea 54% and depression 51%. Less common (reported by <50%) included urinary hesitancy, vomiting, pruritus, wheezing, nightmares and hallucinations. While frequent, the "side effects" tended to be only mild-moderate in severity, not very distressing, and often not attributed to the morphine (see Table). A full analysis of the effect of variables such as age, gender, performance status, survival, formulation, dose, changes in dose, duration of treatment and concomitant medications on side effects profile will be presented.
SYMPTOM
%
average severity
average frequency
average distress
definitely due to
M %
dry mouth
86
moderate
most days-every day
a little
37
sedation
78
moderate
most days-every day
a little
35
constipation
72
moderate
most days
a little – quite a bit
36
Myoclonus
66
mild-mod.
most days
none – a little
27
dizziness
58
mild-mod.
most days
a little
13
confusion
56
mild-mod.
most days
a little – quite a bit
23
nausea
54
mild-mod.
most days
a little
17
depression
51
moderate
most days
a little – quite a bit
3
In conclusion, this survey suggests that, with routine use in patients with advanced cancer, morphine provides good but not complete pain relief while causing "side effects" that are not very troublesome and frequently due to other causes. Much more research into the true nature of morphine side-effects during long-term administration, their prevention and management, and their impact on drug utilisation is required.