Study designs of evaluations included in the review
Double-blinded, randomised controlled trials (RCTs) with either placebo or an active control, and at least 10 participants in each arm of the trial, were eligible for inclusion.
Specific interventions included in the review
Studies of counter irritant or rubefacient, applied at least once daily, were eligible for inclusion. Studies of preparations containing only or mainly capsaicin, or its derivatives, were excluded. The included studies evaluated a range of salicylate-containing gels, creams and ointments. The comparators for studies of acute pain were placebo cream or gel, or homeopathic gel; for studies of chronic pain, the comparators were placebo cream or gel, or 5% etofenamate gel.
Participants included in the review
Studies of people with chronic or acute pain were eligible for inclusion. Studies of oral conditions were excluded. Studies of chronic pain included osteoarthritis, rheumatic disorders and unspecified chronic disorders. Studies of acute pain included low back pain, ankle sprain and unspecified sports injuries. Where reported, the age of the participants ranged from 14 to 86 years.
Outcomes assessed in the review
The primary outcome was improvement in pain. The hierarchy of outcomes in order of preference was: number of patients with a 50% or more reduction in pain (if given), patient-reported global assessment of treatment, pain on movement, pain on rest or spontaneous pain, and physician or investigator global assessment of treatment. The secondary outcomes were adverse events and withdrawal due to adverse events. To be eligible for inclusion, studies had to report the outcomes after at least 3 days for acute conditions and after at least 7 days for chronic conditions. Only trials reporting dichotomous data were included in the efficacy analysis; those reporting only mean or median pain relief, reduction in pain, or continuous data were excluded from this analysis.
How were decisions on the relevance of primary studies made?
At least two reviewers independently assessed trials for inclusion, which were verified by another reviewer. Any disagreements were resolved by consensus.