Efficacy and Safety of Topical Bimatoprost Solution 0.03% in Stable Vitiligo:A Preliminary Study

Vitiligo is an acquired depigmentation disorder of great cosmetic importance, affecting 1-4% of the world's population. Vitiligo does not cause physical symptoms but because of its unsightly appearance, particularly on dark or tanned skin it can have considerable impact both psychologically and socially. Many ways of restoring normal colour to the skin have been tried but improvement is usually short-lived. The causes of vitiligo are not yet clearly understood, so many treatments have been developed on the basis of limited scientific evidence. There is no cure, and no way of limiting the spread of the disease has so far been found.

The pathogenetic basis of the disease is melanocyte disappearance from achromic patches and experimental evidence has shown that three possible mechanisms enable this to occur: an apoptotic process, a necrotic event, and melanocythoragy following trauma due to impaired function of cell-cell or cell-matrix adhesion.

Prostaglandins (PGs) are biologically active derivatives of 20 carbon atom polyunsaturated essential fatty acids released from cell membrane phospholipids. PGE2 and PGF2 are primary PGs. PGE2 is synthesized in skin and affects keratinocytes, Langerhans cells and melanocytes and regulates melanocyte proliferation. Epidermal melanocytes synthesize melanin in response to ultraviolet radiation (UVR). The mechanisms mediating the UVR-induced activation of melanogenesis are unknown but, as UVR induces the turnover of membrane phospholipids generating prostaglandins (PGs) and other products, it is possible that one of these might provide the activating signal. 1 In an in vitro study by Tomita et al .,2 normal human epidermal melanocytes became swollen and more dendritic when they were cultured with prostaglandin E 2 (PGE 2), but not with PGE 1. In another study by Nordlund et al ., 3 PGE2 applied topically to mice skin caused an increase in melanocyte density.

Histologic studies indicate that PGE 2 also enhances melanogenesis. Recently, there have been many reports of iris darkening, hyperpigmentation of the eyelashes, and periocular hyperpigmentation induced by latanoprost . (prostaglandin F 2 α , used for the treatment of glaucoma). 4,5 Although the exact mechanism of this pigmentation is not clear, different mechanisms of the induction of hyperpigmentation by prostaglandins have been suggested, including: (i) influencing the responsiveness of melanocytes to neuronal stimuli; (ii) causing melanocyte proliferation; and (iii) a direct or second messenger mediated interaction with melanocytes via the stimulation of tyrosinase activity.

Phototherapy and topical agents such as corticosteroids, calcineurin inhibitors, and vitamin-D derivatives are basic treatment modalities have been used in vitiligo but there is still no effective and safe treatment for this disease. Resistance to therapy, treatment complications and recurrence after treatment are the major problems of the current treatments.