Background: Multimodal pain is comprised of nociceptive/inflammatory and neuropathic components. Pharmacological pain therapies from different classes provide pain relief using different mechanistic actions; often a combination of such therapies provides more effective pain relief than monotherapy. To assess whether pain management is adequate requires a comprehensive pain scoring system.
Objective: To evaluate the adequacy of a low-dose combination of oxycodone and paracetamol (acetaminophen) in patients with multimodal, chronic, non-malignant pain using the Pain Management Index (PMI).
Methods: During this prospective, observational study, consecutive patients were classified according to the presence of prevalent osteoarticular pain (group A, n = 78) or prevalent neuropathic pain (group B, n = 72). Existing pain-relief medications were discontinued and both groups received oxycodone 5 mg and paracetamol 325 mg up to 8 hourly for a planned duration of >/= 6 weeks. Patients in group B who were receiving gabapentin continued this treatment up to a maximum daily dosage of 2400 mg during the observation period. Pain intensity was evaluated using a visual analogue scale (VAS from 0 to 10). Functional limitation for patients in group A was evaluated using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). The intensities of dynamic allodynia and hyperalgesia in patients in group B were evaluated by a VAS. Results from the WOMAC, dynamic allodynia, and hyperalgesia assessments were evaluated using the PMI.
Results: In group A, 64.3% of patients showed improvements in pain symptoms after 15 days of treatment in the WOMAC categories of "pain preventing sleep" and "walks with aid". The PMI showed that the oxycodone/paracetamol therapy was adequate in patients with osteoarticular pain. In group B, 83.3% of patients reported improvement in the category of "pain preventing sleep", and all patients rated the remaining four categories ("spontaneous pain", "burning pain", "painful paresthesia", and "pinprick") as either stable or improved after 15 days of treatment. Using the PMI, hyperalgesia resolved with oxycodone/paracetamol therapy. 37.1% and 58.3% of patients did not complete the study in group A and B, respectively.
Conclusion: The PMI was an effective tool for assessment of pain management efficacy. Oxycodone/paracetamol improved pain symptoms in the majority of compliant patients. In patients with neuropathic pain, rescue therapy with oxycodone/paracetamol showed a lesser, but significant, improvement of pain symptoms.