Background: Addition of nonopioid analgesic drugs reduces pain and opioid requirements in acute low back pain. In noncancer chronic low back pain (CLBP), the efficacy of a combined regimen to reduce breakthrough pain has not been proven so far.
Objective: Evaluation of the effects of intravenous (i.v.) nonopioid analgesic drugs on pain intensity and lumbar mobility in CLBP patients on chronic opioid therapy.
Design: Randomised, placebo-controlled, double blinded, crossover study.
Setting: Vienna General Hospital, Austria, from December 2002 to May 2004.
Patients: Thirty-six adults with CLBP on chronic opioid therapy. Inclusion criteria are as follows: American Society of Anesthesiologists' physical status less than 3, visual analogue scale (VAS) more than 4 and no known allergy to any of the used drugs.
Intervention: After written informed consent and VAS assessment, any oral nonopioid analgesic drug (NSAIDs, metamizol, paracetamol) was replaced by placebo 10 days before the first test infusion as a washout period. Coanalgesics (anticonvulsants, antidepressants) were maintained. Each patient received randomly four i.v. test infusions of diclofenac 75 mg (and orphenadrine 30 mg), parecoxib 40 mg, paracetamol 1 g and isotonic saline. A washout time of 72 h was allowed between each infusion.
Main outcome measures: Primary outcome was as follows: VAS pain intensity (0 to 100 mm) at inclusion, before and within 30 min after infusion. Secondary outcomes were as follows: Roland-Morris questionnaire, McGill pain questionnaire and a test panel of physical functioning for spinal mobility, muscular endurance, balance and coordination. The differences in means of the above assessments among the groups were analysed.
Results: We found an improvement in VAS from the day of inclusion to the day of each appointment. We observed no improvement in pain intensity (VAS) or in any of the physical functioning tests immediately before versus after administration of the four i.v. drugs. Reductions in sensory, affective and cognitive dimensions of the McGill pain questionnaire were statistically significant in the diclofenac group. A trend of McGill pain questionnaire improvement existed in the other groups.
Conclusion: The present data show that the anticipation of an i.v. infusion of nonopioid analgesic drug improves VAS significantly, probably through expectation-related mechanisms. However, single dose i.v. infusions of nonopioid analgesic drugs fail to improve pain intensity and spinal mobility in CLBP patients on chronic opioid treatment, even immediately after the infusion.