Basic Pharmacology of Topical Imiquimod, 5-Fluorouracil, and Diclofenac for the Dermatologic Surgeon

Heights Dermatology, Houston, Texas 77008, USA.
Dermatologic Surgery (Impact Factor: 1.56). 10/2011; 38(1):97-103. DOI: 10.1111/j.1524-4725.2011.02194.x
Source: PubMed

ABSTRACT Ultraviolet radiation (UVR) contributes to the vast majority of nonmelanoma skin cancer (NMSC). As the incidence of NMSC continues to rise, topical therapies will be used with increasing frequency. Topical therapies may benefit high-risk surgical candidates as an alternative treatment modality and may improve overall cosmesis. The most commonly employed topical therapies are imiquimod, 5-fluorouracil (5-FU), and diclofenac.
To review the detailed mechanism of action and side-effect profiles of each topical therapy used to treat NMSC and to explore newly discovered actions. Uncommon adverse events are also presented.
An extensive literature search was performed to describe the pharmacologic actions of imiquimod, 5-FU, and diclofenac.
A keen understanding of the pharmacologic concepts of these topical therapies may aid the dermatologic surgeon in making sound choices before, during, and after surgery.

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    ABSTRACT: The combination of skin ablation and 5-Fluorouracil (5-FU) ointment was previously tried in the treatment of vitiligo, and good results were specifically reported in glabrous skin without follicular melanocyte reservoirs. Methods. This study was carried out on the skins of seven guinea pigs: three were treated with mechanical dermabrasion plus topical 5-FU in an achromic area contiguous to a pigmented area; two were treated by only dermabrasion in a similar area; and two were treated by topical 5-FU alone. Clinical, histological, and ultrastructural studies were performed over two months. Results. In guinea pigs treated with dermabrasion plus 5-FU, we observed firstly a delay of wound healing with an obvious inflammatory reaction, and, after two months, evident pigment spread from the pigmented into the achromic area. After six months, we noticed black hair regrowing in the achromic area. Pigment spread was not seen in the guinea pigs skin treated by either dermabrasion or topical 5-FU. We suggest that the inflammatory mediators and enzymes (metalloproteinases), which are locally released over a long time, could stimulate and facilitate melanocyte proliferation and migration through the enlarged intercellular spaces of the epidermis. This sequence of events may be applied to vitiligo patients treated with 5-FU on ablated lesions.
    04/2013; 2013:852497. DOI:10.1155/2013/852497
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    ABSTRACT: Background Malignant melanoma is a form of skin cancer associated with significant mortality once it has spread beyond the skin. Melanoma in situ (MIS) is the earliest histologically recognisable stage of malignant melanoma and represents a precursor of invasive melanoma. Lentigo maligna (LM) represents a subtype of pre-invasive intraepidermal melanoma associated specifically with chronic exposure to ultraviolet (UV) radiation. Over the past two decades, the incidence of MIS has increased significantly, even more than the invasive counterpart. There are several treatment options for MIS, but no consensus exists on the best therapeutic management of this condition. Objectives To assess the effects of all available interventions, surgical and non-surgical, for the treatment of melanoma in situ, including LM. Search methods We searched the following databases up to November 2014: the Cochrane Skin Group Specialised Register, CENTRAL in The Cochrane Library (2014, Issue 10), MEDLINE (from 1946), Embase (from 1974), LILACS (from 1982), African Index Medicus (from inception), IndeMED of India (from inception), and Index Medicus for the South-East Asia Region (IMSEAR) (from inception). We scanned the references of included and excluded studies for further references to relevant trials and searched five trials registries. We checked the abstracts of major dermatology and oncology conference proceedings, and we shared our lists of included and excluded studies with industry contacts and other experts in the field of melanoma to try to identify further relevant trials. Selection criteria We included randomised controlled trials (RCT) on the management of MIS, including LM, that compared any intervention to placebo or active treatment. We included individuals, irrespective of age and sex, diagnosed with MIS, including LM, based on histological examination. Data collection and analysis Two authors independently evaluated possible studies for inclusion; extracted data from the included study using a standard data extraction form modified for our review; assessed risk of bias; and analysed data on efficacy, safety, and tolerability. They resolved any disagreements by discussion with a third author. We collected adverse effects information from included studies. Main results Our search identified only 1 study eligible for inclusion (and 1 ongoing study in active recruitment stage), which was a single centre, open label, parallel group, 2-arm RCT with 90 participants, who had 91 histologically proven LM lesions. Forty-four participants, with 44 LM lesions, were treated with imiquimod 5% cream 5 days per week plus tazarotene 0.1% gel 2 days/ week for 3 months, and 46 participants, with 47 LM lesions, were treated with imiquimod 5% cream 5 days per week for 3 months. Two months after cessation of topical treatment, the initial tumour footprint was excised using 2 mm margins via a staged excision. This study was open label, and analysis was not intention-to-treat, leading to a high risk of incomplete outcome data. Our primary outcome 'Histological or clinical complete response' was measured at 5 months in 29/44 participants (66%) treated with imiquimod plus tazarotene (combination therapy) and 27/46 participants (59%) treated with imiquimod (monotherapy). The difference was not statistically significant (risk ratio (RR) 1.12, 95% confidence interval (CI) 0.81 to 1.55, P value = 0.48). With regard to our secondary outcomes on recurrence and inflammation, after amean follow up of 42 months, no local recurrences were observed among complete responders. Difference in overall inflammation score between the 2 groups was significant (mean difference (MD) 0.6, 95% CI 0.2 to 1, P value = 0.004), with the mean overall inflammation score being significantly higher in the combination group. The study authors did not clearly report on side-effects. Because of adverse effects, there was a dropout rate of 6/44 participants (13.7%) in the combination group compared with 1/46 (2.2%) in the imiquimod monotherapy group (due to excessive inflammation) before the cessation of topical treatment (first 3 months), but this was not statistically significant (RR 6.27, 95% CI 0.79 to 50.02, P value = 0.08). Authors' conclusions There is a lack of high-quality evidence for the treatment of MIS and LM. For the treatment of MIS, we found no RCTs of surgical interventions aiming to optimise margin control (square method, perimeter technique, 'slowMohs', staged radial sections, staged "mapped" excisions, or Mohs micrographic surgery), which are the mostwidely used interventions recommended as first-line therapy. The use of non-surgical interventions in selected cases (patients with contraindications to surgical interventions) may be effective and may be considered preferable for experienced providers and under close and adequate follow up. For the treatment of LM, we found no RCTs of surgical interventions, which remain the most widely used and recommended available treatment. The use of non-surgical interventions, such as imiquimod, as monotherapy may be effective and may be considered in selected cases where surgical procedures are contraindicated and used preferentially by experienced providers under close and adequate follow up. The use of topical therapies, such as 5-fluorouracil and imiquimod, as neoadjuvant therapies warrants further investigation. There is insufficient evidence to support or refute the addition of tazarotene to imiquimod as adjuvant therapy; the current evidence suggests that it can increase topical inflammatory response and withdrawal of participants because of treatment-related side-effects.
    Cochrane database of systematic reviews (Online) 12/2014; 12(12):CD010308. DOI:10.1002/14651858.CD010308.pub2 · 5.70 Impact Factor
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    ABSTRACT: BACKGROUND The antimetabolite 5-fluorouracil (5-FU) is used for topical treatment of actinic keratosis. Overall improvement in the skin is also observed. Additionally, 5-FU was reported to be used for superficial peels. OBJECTIVES To evaluate the efficacy and safety of 5% 5-FU cream compared with peels for photodamaged forearms. METHODS This interventional, randomized, comparative, evaluator-blind study included 32 patients with severe photoaging of forearms. The regimens comprised either application of 5% 5-FU cream everyday for 4 weeks on 1 forearm and 4 weekly peels on the other. Efficacy assessment included: clinical photodamage scores, opinion of patients and investigators, and blind photographic evaluation by independent observers. Skin biopsies were performed for histologic and immunohistochemical analysis. Safety evaluation comprised observation of adverse events. RESULTS Clinical and histologic findings confirmed the benefits of topical 5% 5-FU, in cream or peels, which improved skin appearance and decreased the dermal elastotic material. Immunohistochemistry showed reduced levels of epidermal p53 and increase in the level of procollagen I. Results were maintained after 6 months. Predictable adverse events occurred, with no differences between treatments. Patients reported better tolerability to peels. CONCLUSION Five percent 5-FU cream or peels was safe and effective for the treatment of photodamaged forearms. Decreased epidermal p53 levels and new dermal collagen were confirmed.
    Dermatologic Surgery 06/2014; 40(6):610-7. DOI:10.1111/dsu.0000000000000024 · 1.56 Impact Factor