Clinical effectiveness of Diclofenac Epolamine: Transdermal patch

Diclofenac epolamine is a non-opioid analgesic that is used to relieve pain from a number of different conditions. It is a nonsteroidal anti-inflammatory drug (NSAID) commonly used for conditions such as rheumatic conditions and epicondylitis (such as tennis or golf elbow). Whilst it has historically been administered orally, there are now transdermal patches available on an over the counter basis to help reduce pain and inflammation.

Is transdermal diclofenac epolamine effective?

A number of studies have taken place examining the role of the transdermal topical patch containing 1.3% of Diclofenac Epolamine in patients with acute pain, with the majority of trials focusing on soft tissue injuries such as ankle sprains and tendinous inflammation.

A recent systematic review, undertaken by the University of York in the UK, considered six randomised placebo-controlled trials containing over 1400 participants, and one open label study with 100 participants, in determining the efficacy and tolerability of the transdermal patch (1). The study found that the topical patch was associated with reduced pain in soft tissue injuries when compared with placebo over a 7-14 day period, with spontaneous pain reduced significantly from baseline when compared to both placebo and DDA topical gel (60.8% vs 40.8%). Pain resolution was reported as occurring on average 72 hours earlier when transdermal patches were used as opposed to no intervention (2).

Although the evidence base is relatively small in size, the studies that do exist are generally well designed, acknowledge all potential sources of bias, and state that transdermal patches significantly reduce pain in patients with soft tissue injuries.

Are the transdermal patches safe?

Of the 7 studies that were reviewed as part of the systematic review, 5 reported side effects that are relatively common with many NSAIDS – application site reactions (such as rash and dermatitis) and gastrointestinal symptoms (nausea). However, many of these side effects were also reported in patients who had taken the placebo, so it remains unclear as to the true level of side effects that transdermal patches may have on patients. The studies undertaken so far suggest that any side effects are relatively minor and not uncommon to many other analgesics that are available on the market, yet there is still some reticence to recommend transdermal patches to some patient groups due to a wide range of known side effects in other NSAIDs.

Patients who are hypersensitive to diclofenac, or those who have experienced asthma, urticaria or allergic reactions after taking any other NSAID are generally advised to use the drug with caution in any of its applications.

The patches are contraindicated in the treatment of peri-operative pain following cardiac artery bypass graft surgery, and patients who have eczema, infected lesions, dermatitis or wounds should also avoid applying the patch near any of these sites on their skin.

Patients with a prior history of intestinal bleeding or ulcer disease are also rarely prescribed NSAIDs. As there are no longer term studies regarding the safety and long term effects of using transdermal patches, some pharmacists may be hesitant to advice on this method of application for patients with certain medical histories.

How does the effectiveness and safety of diclofenac epolamine (transdermal) compare with its oral administration?

There is very little comparative research available in regards to the efficacy and tolerability of topical vs oral diclofenac epolamine analgesics. As the topical patches are new to market, most of the literature that currently exists is concerned with it in isolation and does not answer questions regarding its effectiveness and tolerability in relation to other products on the market.

A pooled analysis of 14 studies, carried out by a group of medical researchers in Colorado, found that the topical patches demonstrated a low incidence of gastrointestinal side effects. The study states that this makes the patches a viable alternative to short term oral NSAIDs that have been evidenced to have gastrointestinal side effects (such as diclofenac potassium), yet this may simply be a legacy of other NSAIDs being heavily researched and understood in comparison to a relatively new drug to market. Most comparative studies only consider transdermal patches in relation to placebo (2).

There is some indication in wider systematic reviews of NSAID efficacy and tolerability that transdermal patches, and diclofenac gels, are more effective than other options that are available on the market.

A Cochrane Database Systematic Review, undertaken earlier this year and covering over 60 studies and 15,000 study participants, compared a range of different studies and found that gel formations of diclofenac provided the best effects (3). The study also highlighted that the evidence for transdermal patches was strong, noting that the literature for topical diclofenac had grown considerably over the past three years.

There are a limited number of studies comparing other diclofenac applications, with another 2015 Cochrane Review concluding that diclofenac potassium provides good pain relief for acute postoperative pain at 25, 50 and 100mg doses. The review concluded that diclofenac sodium was not appropriate for the treatment of acute pain, but there is no available information on transdermal patches for this particular type of acute trauma (4).

In conclusion, diclofenac transdermal patches are effective in the treatment of acute pain associated with particular injuries and are generally considered to be the equally most effective NSAID on the market. There is no available literature directly comparing oral and topical sodium diclofenac, and the small amount of literature comparing diclofenac gel with other NSAID gels on the market is also relatively limited. More research and well designed studies are required to add to the understanding of diclofenac gels in the treatment of acute physical injury. 

References

1. Kuehl KS (2011) Review of the efficacy and tolerability of the diclofenac epolamine topical patch 1.3% in patients with acute pain due to soft tissue injuries Cent Review Dissem

2. Kuehl KS, Carr W, Yanchick J, Magelli M, Rovati S (2011) Analgesic efficacy and safety of the diclofenac epolamine topical patch 1.3% (DETP) in minor soft tissue injury Int J Sports Med 32(8):635-43

3. Derry S, Moore RA, Gaskell H, McIntyre M, Wiffen PJ (2015) Topical NSAIDs for acute musculoskeletal pain in adults Coch Data Syst Rev doi: 10.1002/14651858.CD007402.pub3

4. Derry S, Wiffen PJ, Moore RA (2015) Single dose oral diclofenac for acute postoperative pain in adults COch Data Syst Rev CD004768 [Epub ahead of print]