Introduction
Hydroquinone (HQ), which has been used for more than 50 years, is often described as the gold
standard of skin lightening. Despite its general effectiveness, however, some patients never
achieve adequate reductions in pigmentation.
HQ inhibits tyrosinase by binding histidines or
copper at the active site of the enzyme.The clinical effectiveness of HQ 4% in the treatment
of melasma and other pigment disorders has been shown in multiple studies, both as monotherapy
and in combination with other ingredients.
Based on observation of a loss of effectiveness after long-term treatment with HQ, researchers
hypothesize that after constant exposure to HQ, melanocytes eventually become resistant to it,
which leads to increased production of melanin (rebound pigmentation) and potential development
of ochronosis. However, with a pulse treatment protocol, the patient is initially treated with HQ
for 4 to 6 weeks to establish a baseline level of skin lightening, followed by a 4 to 6 week interval
to allow the skin to stabilize by treatment with retinol, antioxidants, and anti-inflammatory agents.
With this protocol, the clinician can use HQ in rotation with other products as needed without
losing efficacy and can extend the period between HQ treatments.
IntroductionHydroquinone (HQ), which has been used for more than 50 years, is often described as the goldstandard of skin lightening. Despite its general effectiveness, however, some patients neverachieve adequate reductions in pigmentation. HQ inhibits tyrosinase by binding histidines or copper at the active site of the enzyme.The clinical effectiveness of HQ 4% in the treatmentof melasma and other pigment disorders has been shown in multiple studies, both as monotherapyand in combination with other ingredients.Based on observation of a loss of effectiveness after long-term treatment with HQ, researchershypothesize that after constant exposure to HQ, melanocytes eventually become resistant to it,which leads to increased production of melanin (rebound pigmentation) and potential developmentof ochronosis. However, with a pulse treatment protocol, the patient is initially treated with HQfor 4 to 6 weeks to establish a baseline level of skin lightening, followed by a 4 to 6 week intervalto allow the skin to stabilize by treatment with retinol, antioxidants, and anti-inflammatory agents.With this protocol, the clinician can use HQ in rotation with other products as needed withoutlosing efficacy and can extend the period between HQ treatments.
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