Original Research
Imiquimod Cream 2.5% and 3.75% Applied Once Daily to Treat External Genital Warts in Men
We assess the safety and efficacy of imiquimod cream 3.75% and 2.5% in men with external genital warts (EGWs).
Epidermal melasma is a common hyperpigmentation disorder that can be challenging to treat. The pathogenesis of melasma is not fully understood but has been associated with increased melanin and melanocyte activity.1,2 Melasma is characterized by jagged, light- to dark-brown patches on areas of the skin most often exposed to the sun—primarily the cheeks, forehead, upper lip, nose, and chin.3 Although it can affect both sexes and all races, melasma is more common in Fitzpatrick skin types II to IV and frequently is seen in Asian or Hispanic women residing in geographic locations with high levels of sun exposure (eg, tropical areas).2 Melasma presents more frequently in adult women of childbearing age, especially during pregnancy, but also can begin postmenopause. Onset may occur as early as menarche but typically is observed between the ages of 30 and 55 years.3,4 Only 10% of melasma cases are known to occur in males4 and are influenced by such factors as ethnicity, hormones, and level of sun exposure.2
Topical therapies for melasma attempt to inhibit melanocytic activation at each level of melanin formation until the deposited pigment is removed; however, results may vary greatly, as melasma often recurs due to the migration of new melanocytes from hair follicles to the skin’s surface, leading to new development of hyperpigmentation. The current standard of treatment for melasma involves the use of hydroquinone and other bleaching agents, but long-term use of these treatments has been associated with concerns regarding unstable preparations (which may lose their therapeutic properties) and adverse effects (eg, ochronosis, depigmentation).5 Cosmetic agents that recently have been evaluated for melasma treatment include nicotinamide (a form of vitamin B3), which inhibits the transfer of melanosomes from melanocytes to keratinocytes; arbutin, which inhibits melanin synthesis by inhibiting tyrosinase activity6; bisabolol, which prevents anti-inflammatory activity7; and retinaldehyde (RAL), a precursor of retinoic acid (RA) that has powerful bleaching action and low levels of cutaneous irritability.8
This prospective, single-arm, open-label study, evaluated the efficacy and safety of a novel cream formulation containing nicotinamide 4%, arbutin 3%, bisabolol 1%, and retinaldehyde 0.05% in the treatment of epidermal melasma.
Study Product Ingredients and Background
Nicotinamide
Nicotinamide is a water-soluble amide of nicotinic acid (niacin) and one of the 2 principal forms of vitamin B3. It is a component of the coenzymes nicotinamide adenine dinucleotide and nicotinamide adenine dinucleotide phosphate. Nicotinamide essentially acts as an antioxidant, with most of its effects exerted through poly(adenosine diphosphate–ribose) polymerase inhibition. Interest has increased in the role of nicotinamide in the prevention and treatment of several skin diseases, such as acne and UV radiation–induced deleterious molecular and immunological events. Nicotinamide also has gained consideration as a potential agent in sunscreen preparations due to its possible skin-lightening effects, stimulation of DNA repair, suppression of UV photocarcinogenesis, and other antiaging effects.9
Arbutin
Arbutin is a molecule that has proven effective in treating melasma.10 Its pigment-lightening ingredients include botanicals that are structurally similar to hydroquinone. Arbutin is obtained from the leaves of the bearberry plant but also is found in lesser quantities in cranberry and blueberry leaves. A naturally occurring gluconopyranoside, arbutin reduces tyrosinase activity without affecting messenger RNA expression.11 Arbutin also inhibits melanosome maturation, is nontoxic to melanocytes, and is used in Japan in a variety of pigment-lightening preparations at 3% concentrations.12
Bisabolol
Bisabolol is a natural monocyclic sesquiterpene alcohol found in the oils of chamomile and other plants. Bisabolol often is included in cosmetics due to its favorable anti-inflammatory and depigmentation properties. Its downregulation of inducible nitric oxide synthase and cyclooxygenase-2 suggests that it may have anti-inflammatory effects.7
Retinaldehyde
Retinaldehyde is an RA precursor that forms as an intermediate metabolite in the transformation of retinol to RA in human keratinocytes. Topical RAL is well tolerated by human skin, and several of its biologic effects are identical to those of RA. Using the tails of C57BL/6 mouse models, RAL 0.05% has been found to have significantly more potent depigmenting effects than RA 0.05% (P<.001 vs P<.01, respectively) when compared to vehicle.13
Although combination therapy with RAL and arbutin could potentially cause skin irritation, the addition of bisabolol to the combination cream used in this study is believed to have conferred anti-inflammatory properties because it inhibits the release of histamine and relieves irritation.
Methods
This single-center, single-arm, prospective, open-label study evaluated the efficacy and safety of a novel cream formulation containing nicotinamide 4%, arbutin 3%, bisabolol 1%, and RAL 0.05% in treating epidermal melasma. Clinical evaluation included assessment of Melasma Area and Severity Index (MASI) score, photographic analysis, and in vivo reflectance confocal microscopy (RCM) analysis.
