Topic diclofenac, in its gel formulation, is widely used (above all as an OTC drug) in knee and hand osteoarthritis pain. With a randomized trial, sponsored by pharmaceutical industry, 385 patients with osteoarthritis pain have been treated with diclofenac gel (4 applications a day for 8 weeks) or with a gel with no active substance. All patients had undergone an X-ray exam, showing interphalangeal or carpal-metacarpal osteoarthritis. Symptoms were evaluated through an analogical score scale, combined with a function index relative to pain and joint stiffness. Diclofenac resulted better than placebo, on all considered parameters, of 5-7 points out of 100. Some differences have reached statistical significance, some others didn’t, with P values ranging from 0.06 to 0.11, with similar values also for treatment discontinuation due to side effects (dermatitis): about 5% of subjects treated with the active drug and about 2% of the ones treated with gel have suspended applications.
Diclofenac gel has better pain lenitive properties than a neutral gel, but obtainable results are not impressive. Considering the fact that gel absorption, even if very little, occurs, it would be necessary to establish whether the mild obtainable improvement is due to local action or rather to systemic one (the gel causes blood levels of diclofenac equal to about 6% of the ones obtainable with an oral administration). In the end, we have to consider the quite high cost of this topic product.
