aRTicle | dermatology | Table 1 Fitzpatrick Skin Type Scale
Skin type Skin colour I
II III IV V VI
Hydroquinone preparations are the most extensively used in the treatment of melasma14
Characteristics
White; very fair; red or blond hair; blue eyes; freckles
Cream white; fair with any eye or hair colour; very common
Brown; typical Mediterranean Caucasian skin
Dark brown; mid-eastern skin types Black Always burns, never tans
White; fair; red or blond hair; blue, hazel, Usually burns, tans or green eyes
with difficulty
Sometimes mild burn, gradually tans
Rarely burns, tans with ease
Very rarely burns, tans very easily
Never burns, tans very easily in a concentration
varying from 2% (over-the-counter) to 5% (prescription only). typically, 4–6 weeks are required for a visible response, but the clearance of melasma may take up to 6 months2
. ennes et al13 , comparing 4% and 3% versus 6%
hydroquinone preparations, did not find any significant difference in clinical efficacy. Hydroquinone can also be used in combination with other agents. adverse reactions to hydroquinone (which
are both dose- and time-related) include erythema, stinging, colloid milium, irritant and allergic contact dermatitis, nail discoloration, and paradoxical post-inflammatory hypermelanosis2, 13, 14
. regulatory agencies in Japan, europe, and
more recently, the USa, have raised concerns with regard to the safety of hydroquinone, and it has been banned in cosmetic preparations in many countries. this has encouraged research into alternative agents for the topical management of melasma15
.
Methimazole methimazole is an oral antithyroid compound, used for the treatment of hyperthyroidism, that exhibits a skin-depigmenting effect when used topically. methimazole is a potent inhibitor of peroxidases and its antithyroid effect is a result of its ability to inhibit thyroid peroxidase activity16
. melanocyte peroxidase is a vital
enzyme responsible for mediating a number of steps in the biosynthesis of melanins. the inhibition of peroxidase by methimazole could interfere with melanin synthesis at different stages, explaining its depigmenting action on the skin. Kasraee et al16
showed that topical methimazole 5%
caused a moderate-to-marked improvement of the hyperpigmentation lesions within a few weeks of treatment16
. It is a non-cytotoxic and non-mutagenic
compound, is well tolerated, and does not affect the level of serum thyroid hormones (free triiodothyronine (Ft3), free thyroxine (Ft4), thyroid-stimulating hormone (tSH)). topical methimazole is well tolerated by the
20 ❚ July 2011 |
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Zinc sulfate 10% solution topical zinc ions have been reported to provide antioxidant photoprotection for the skin21
. Khalifa et al showed that 10% topical zinc sulfate is an effective agent in melasma by
Regulatory agencies in Japan, europe,
and more recently, the
Usa, have raised concerns with regard to the safety of hydroquinone, and it has been banned
in cosmetic preparations in many countries.
patient and does not induce any significant cutaneous side-effects16
.
Pidobenzone Pidobenzone 4% acts by inhibiting tyrosinase activity, the enzyme involved in the production of melanin. In one study17
, the successful treatment of pidobenzone
4% in melasma is described. twenty female patients (with phototypes from II to IV, according the Fitzpatrick Skin type Scale) were treated with pidobenzone and evaluated 3 months later, at which point the participants showed a complete (100%) regression of skin hyperpigmentation in the cases of epidermal melasma, and a good response (from 50% to 75%) in the cases of mixed melasma. No side-effects were observed either during or after treatment17
.
Tretinoin also known as all-trans retinoic acid (atra), topical tretinoin 0.05–0.1% reduces pigmentation by inhibition of tyrosinase transcription and
significant thickening of the granular layer and epidermis as a whole; neither the number of melanocytes is affected, nor is there evidence of melanocyte damage18
. as compared with phenolic compounds, atra has to
be applied for a greater length of time — significant lightening becomes evident after 24 weeks. Published clinical trials show a good clinical efficacy of atra in monotherapy, but better results are obtained in combination with other compounds, such as hydroquinone and corticosteroids19, 20
. the most common side-effects are erythema, peeling,
burning and stinging. It should be emphasised that the use of total sun block is mandatory during the atra treatment. other retinoids used in the treatment of melasma include isotretinoin, tazarotene and adapalene19
.
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