Paracetamol Combination Therapy for Back Pain and Osteoarthritis: A Systematic Review and Meta-Analyses

Background and Objective Although paracetamol (acetaminophen) combined with other analgesics can reduce pain intensity in some pain conditions, its effectiveness in managing low back pain and osteoarthritis is unclear. This systematic review investigated whether paracetamol combination therapy is more effective and safer than monotherapy or placebo in low back pain and osteoarthritis. Methods Online database searches were conducted for randomised trials that evaluated paracetamol combined with another analgesic compared to a placebo or the non-paracetamol ingredient in the combination (monotherapy) in low back pain and osteoarthritis. The primary outcome was a change in pain. Secondary outcomes were (serious) adverse events, changes in disability and quality of life. Follow-up was immediate (<= 2 weeks), short (> 2 weeks but <= 3 months), intermediate (> 3 months but < 12 months) or long term (>= 12 months). A random-effects meta-analysis was conducted. Risk of bias was assessed using the original Cochrane tool, and quality of evidence using Grading of Recommendations Assessment, Development and Evaluation (GRADE). Results Twenty-two studies were included. Pain was reduced with oral paracetamol plus a non-steroidal anti-inflammatory drug (NSAID) at immediate term in low back pain (paracetamol plus ibuprofen vs ibuprofen [mean difference (MD) - 6.2, 95% confidence interval (CI) -10.4 to -2.0, moderate evidence]) and in osteoarthritis (paracetamol plus aceclofenac vs aceclofenac [MD - 4.7, 95% CI - 8.3 to - 1.2, moderate certainty evidence] and paracetamol plus etodolac vs etodolac [MD - 15.1, 95% CI - 18.5 to - 11.8; moderate certainty evidence]). Paracetamol plus oral tramadol reduced pain compared with placebo at intermediate term for low back pain (MD - 11.7, 95% CI - 19.2 to - 4.3; very low certainty evidence) and osteoarthritis (MD - 6.8, 95% CI - 12.7 to -0.9; moderate certainty evidence). Disability scores improved in half the comparisons. Quality of life was infrequently measured. All paracetamol plus NSAID combinations did not increase the risk of adverse events compared to NSAID monotherapy. Conclusions Low-to-moderate quality evidence supports the oral use of some paracetamol plus NSAID combinations for short-term pain relief with no increased risk of harm for low back pain and osteoarthritis compared to its non-paracetamol monotherapy comparator.