๐ ็ธฝ็ฎ้ ๏ฝ ๐ ่ฑๆๅๆ๏ผๆฌ็ฏ๏ผ ๏ฝ ๐ ๅฎๆด็ฟป่ญฏ ๏ฝ โญ ็ฒพ่ฏ็ญ่จ
Hydroquinone
Hydroquinone
HQ is a mainstay topical depigmenting agent in the treatment of dyschromias,
particularly melasma and PIH. Its mechanism of melanogenesis disruption is brought about by the inhibition of the conversion of tyrosine to L-3,4- dihydroxyphenylalanine (L-DOPA) and its eventual conversion into melanin.11 HQ is available in 2% concentration as an over-the-counter medication in the United States. Increased concentrations are available through prescription, though generally this is capped at 4% in the United States. It is applied twice daily to affected areas, and known side effects (SE) include irritant and allergic contact dermatitis, nail discoloration, hypopigmentation of surrounding normal skin, and exogenous ochronosis.12 There is increased risk of each of these adverse reactions with increased concentrations of HQ.13 Exogenous ochronosis clinically shows gray-brown hyperpigmentation with associated pinpoint hyperchromic papules and banana-shaped fibers along the papillary dermis on histopathology.14 Patients with long-term use of HQ increase their risk for exogenous ochronosis. If exogenous ochronosis is suspected, application of HQ should be stopped.15 Rodent studies have suggested oral HQ as a possible carcinogen. However, there has been no association found between HQ and cancer in humans.16