Dealing with cancer pain: Low-dose morphine examined

This study compared weak opioids and low-dose morphine in providing pain relief for moderate cancer pain.

Researchers concluded that low-dose morphine is more suitable as pain management for moderate cancer pain than weaker pain relievers.

The guidelines for cancer pain relief developed by the World Health Organization follows three steps: non-opioid (such as aspirin and paracetamol) are administered first; then weak opioids (such as codeine) are given, as necessary, for mild to moderate cancer pain; finally, strong opioids (such as morphine) are administered for moderate to severe cancer pain that does not respond to weaker pain relievers. However, evidence is mixed as to the optimal method of pain relief for cancer patients, while accounting for potential side-effects. 

A total of 240 patients with moderate cancer pain were included in this study. Patients were randomly assigned to receive either a weak opioid (most patients received tramadol or codeine in combination with paracetamol), or low-dose morphine, over the course of 28 days.

A pain relief of 20% or more since the beginning of the study was noted in 88% of patients receiving low-dose morphine, compared to only 55% of patients receiving a weak opioid. Similarly, substantial pain relief (of 50% or more) was more common among patients receiving morphine (76%), compared to those receiving a weak opioid (42%). A significant benefit of low-dose morphine over weak opioid was observed as early as within the first week of treatment, and this was maintained throughout the duration of the study. The need to adjust drug dosage, or switch drug treatment, was also less common among patients receiving treatment with morphine.

Previous studies have demonstrated that opioid treatment is associated with vomiting, constipation, dry mouth, skin irritation, dizziness, fatigue and confusion. However, in this study the rate of reported side-effects was low for both low-dose morphine and weak opioids (less than 5% of patients wished to discontinue treatment due to side-effects).

Researchers concluded that low-dose morphine is more suited at providing pain relief for moderate cancer pain than weak opioids. Researchers also proposed that the three-step guidelines for cancer pain relief should be adapted accordingly.

No information was provided regarding the type or stage of cancer the patients included in this study had. Larger clinical trials that control for different types of cancer, as well as cancer progression and disease outcomes, are needed to confirm these preliminary results.