Hydroquinone Topical
The "gold standard of whitening" powerfully suppressing melanin synthesis
About This Treatment
Hydroquinone is the gold standard whitening topical agent inhibiting tyrosinase to suppress melanin production. Standard concentration is 2-4%. Not insurance-covered in Japan (self-pay/compounded or OTC). One of the most potent whitening ingredients directly inhibiting the rate-limiting enzyme tyrosinase. Efficacy for melasma, solar lentigines, and PIH proven in multiple RCTs. Famous in combination with tretinoin (Kligman formula).
Mechanism of Action
Hydroquinone: ①binds copper active center of tyrosinase blocking tyrosine→DOPA→dopaquinone, ②inhibits melanosome formation within melanocytes, ③selective melanocyte cytotoxicity (high concentration), ④promotes melanin degradation. Multi-step inhibition suppresses new melanin while existing melanin is excreted. Reversible action dependent on tyrosinase activity.
Indications
Expected Results
Visible improvement at 5-7 weeks. 12-week trial: hydroquinone 4% achieved 76.9% pigmentation improvement. Triple combination (Kligman formula: tretinoin 0.05% + hydroquinone 4% + steroid) provides fastest and most significant effect. Effect wanes months after discontinuation; maintenance therapy important.
Clinical Evidence
Risks & Side Effects
Irritant contact dermatitis (erythema, dryness, pruritus) relatively common. Exogenous ochronosis risk with prolonged high-concentration use (>6% for years) - irreversible blue-gray pigmentation. Sun protection mandatory during use. Limited pregnancy safety data (avoidance recommended). Drug holiday recommended after 3-6 months (max continuous use ~5 months).
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