Diclofenac gel treats actinic keratosis
By William T. Elliott, MD, FACP
and James Chan, PharmD, PhD
Diclofenac gel, marketed under the trade name Solaraze, is indicated for the topical treatment of actinic keratosis (AK). It is reaching the market just several months after receiving Food and Drug Administration (FDA) approval. The gel combines the anti-inflammatory diclofenac with hyaluronate sodium, reported to enhance drug delivery to pathological sites,1 for the topical treatment of these common skin lesions.
AK is a common pre-malignant inflammatory skin lesion involving areas of the body exposed to the sun. The prevalence of the disease is believed to be about 25% in the Western Hemisphere and more prevalent in individuals with fair complexion and older than 50 years.2,3 Left untreated, AK may progress to squamous cell carcinoma. Current treatment options range from topical application of 5-fluorouracil or masoprocol to excisional surgery, Mohs surgery, cryosurgery, or radiotherapy, but each has its limitations. Diclofenac gel offers another, perhaps better-tolerated option for treatment of these common skin lesions.
• Clinical Implications.
Diclofenac is a cyclooxygenase inhibitor used widely in the oral form for the treatment of pain and inflammation. It also is used as a topical ophthalmic drop for post-cataract surgery and prior to corneal refractive surgery. The mechanism of action of diclofenac in AK is not known, but it has been proposed that the inhibition of antiangiogenesis may be a mechanism of action.1 In clinical trials reported by the manufacturer, diclofenac gel had a success rate of 18%-47% compared to 10%-20% for the vehicle alone.4 Success was defined as complete clearance of AK lesions 30 days after completion of treatment. Statistical differences were demonstrated for lesions on the forehead and face, but not on the scalp, arm/forearm, and the back of the hand, although numerical advantage was reported for these body locations.
• Dosage.
Diclofenac gel is gently smoothed onto the lesion areas twice daily. The amount should be enough to cover each lesion adequately. Normally 0.5 g of gel is used on each 5 cm x 5 cm lesion site. One-half gram of gel covers about 25 cm of lesion. The recommended duration of therapy is 60-90 days. Diclofenac gel is supplied in tubes of 25 g and 50 g at a strength of 30 mg/g (3% gel strength).
• Nursing considerations.
Diclofenac gel provides an alternative to other topical treatments such as masoprocol and 5-fluorouracil and may be better tolerated in terms of local adverse events. Currently there are no comparative studies with 5-fluorouracil or masoprocol. Common side effects compared to vehicle are contact dermatitis (19% vs. 4%), rash (35% vs. 20%), and dry skin (27% vs. 12%). About 18% of patients discontinue treatment due to side effects compared to 4% for the vehicle.1 Optimal therapeutic effect may not be evident for up to 30 days. Due to some — although low — systemic absorption, diclofenac gel should be used with caution in patients with active gastrointestinal ulcers, or bleeding, or severe renal or hepatic impairment. Also, concomitant administration of nonsteroidal anti-inflammatory drugs (NSAID) should be minimized.4
• Patient education.
Warn patients to avoid exposure to sunlight or sunlamps as well as concomitant use of NSAIDs. The gel should not be applied to open skin wounds, areas of exfoliative dermatitis or infections, and should not be allowed to come in contact with the eyes. The effect and safety of using diclo-fenac gel in combination with dermal products such as cosmetics, sunscreens, and other topical medications is unknown. Patients need to understand the need for monitoring and follow-up, especially should severe dermal reactions (such as irritant or allergic contact dermatitis) occur.
References
1. Seed MP, et al. Cancer Res 1997; 57:1,625-1,629.
2. Peters DC, RH Foster. Drugs Aging 1999; 14:313-319.
3. Frost CA, Green AC. Br J Dermatol 1994; 131:455-464.
4. Solaraze Product Information. SkyePharma. October 2000. n
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