Skin Lightening Agents

Published on 15/03/2015 by admin

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Last modified 15/03/2015

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Chapter 15 Skin Lightening Agents

INTRODUCTION

Hyperpigmentation is a common skin problem that is particularly prevalent in middle-aged and elderly individuals. It is cosmetically important and can greatly detract from both appearance and quality of life, particularly in cultures where smooth skin is valued as a sign of health or in cultures that are beauty conscious. Hyperpigmented skin lesions may be postinflammatory as a sequel to acne, trauma, chemical peels, or laser therapy. Exogenous causes, particularly ultraviolet (UV) light exposure, are a common factor in pigmentary abnormalities such as melasma, solar lentigines, and ephelides (Fig. 15.1). Exposure to certain drugs and chemicals as well as the existence of certain disease states can result in hyperpigmentation (Box 15.1).

The treatment of acquired hyperpigmentation has traditionally been challenging and frequently discouraging. Many of the agents that have been used cause skin irritation, require many months of regular use before results are apparent, or are only partly effective. Patient compliance with therapy must be strict. Sun avoidance and the religious use of a high sun protection factor (SPF) sunblock are mandatory for successful treatment.

SKIN LIGHTENING COSMECEUTICALS

Multiple depigmenting cosmeceuticals are currently available, although published clinical evidence to support their effectiveness is lacking. These skin lightening compounds work by removing undesired pigment by acting at one or more steps in the pigmentation process (Box 15.2). Since tyrosinase is the rate-limiting enzyme for melanin biosynthesis, many of the cosmeceuticals for skin lightening exert their effect on this enzyme.

• Hydroquinone

For many years, the phenolic compound hydroquinone has been the most widely and successfully used skin lightening agent for the treatment of melasma, postinflammatory hyperpigmentation, and other disorders of hyperpigmentation (Fig. 15.2). Hydroquinone occurs naturally in many plants as well as in coffee, tea, beer, and wine. Hydroquinone depigments skin by inhibiting the conversion of tyrosine to melanin. It has been shown to decrease tyrosinase activity by 90%. It may also inhibit DNA and RNA synthesis, as well as degrade melanosomes.

In the US, hydroquinone is available over the counter (OTC) in strengths up to 2%. Most prescription strength hydroquinone formulations contain 3–4%, but concentrations as high as 10% may be available through compounding pharmacies.

Also, several new combination agents are now available in the US. A prescription drug containing 4% hydroquinone, tretinoin, and a low-potency fluorinated steroid, fluocinolone acetonide, is effective and safe in the treatment of melasma. Other combination products contain glycolic acid, vitamin C, and/or retinol to function as penetration enhancers for the hydroquinone active.

Hydroquinone is generally considered safe. Common side effects are skin irritation or contact dermatitis, which can be treated with topical steroids. A rare but serious side effect of hydroquinone is the development of exogenous ochronosis, a sooty hyperpigmentation in the treatment area, which may be difficult to reverse. Exogenous ochronosis appears to be prevalent among darker complected individuals when hydroquinone is used at high concentrations or for prolonged periods even at low concentrations.

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