Inclusion Criteria:

1. Patients diagnosed with malignancy who have persistent pain which is believed by the
investigator to be due to their cancer, and whose analgesic regimen has been
stabilised on > 60mg of morphine equivalents/day.

2. Age > 18 years

3. Performance status of 0-2 by the European Co-operative Oncology Group (ECOG)
Performance Scale

4. Sufficient English skills to be able to complete the daily diary, BPI and to
understand the consent form

5. Signed informed consent

Exclusion Criteria:

1. Patient has no pain (0/10 on NRS).

2. Patients with severe pain are excluded, however once their pain control is optimised
they are eligible.

3. Patient has received radiation therapy in the six weeks prior to commencing the study
or is likely to require radiotherapy during the study period.

4. Patient has commenced, or had dose modifications, to either non-steroidal
anti-inflammatory drugs (NSAIDs) or corticosteroids in the week prior to commencing
the study, or during the two-week study period.

5. Patient has commenced chemotherapy or hormone therapy in the 4 weeks prior to the
study or is expected to commence chemotherapy or hormonotherapy during the study
period. Patients who are stable on long-term chemotherapy or hormones are eligible
for this study. Patients who receive high dose steroids as antiemetics with their
chemotherapy are eligible providing they are not receiving the steroids during the
study period.

6. Patient has a contraindication to acetaminophen.

7. Use of acetaminophen in the 48 hours prior to commencement of the study period.

8. Abnormal laboratory values:

- Absolute neutrophil count < 1.5 X 10^9/L and white blood cell (WBC) count < 3 X
10^9/L

- Platelet count < 100 X 10^9/L

- Liver transaminases > 2.5 X upper limit of normal

- Bilirubin > 1.5 X upper limit of normal

- Creatinine > 1.5 X upper limit of normal