Hydroquinone
Pronunciation: hy-droh-KWIN-ohn
A topical depigmenting agent that inhibits melanin synthesis by blocking the enzyme tyrosinase, used in the treatment of hyperpigmentation and melasma.
Full Definition
Hydroquinone is considered the gold-standard topical agent for hyperpigmentation management in aesthetic dermatology, typically formulated at concentrations of 2–4% in prescription preparations. It acts by inhibiting tyrosinase, the key enzyme in the melanogenesis pathway. Editors should be alert to concentration figures, which are always expressed as percentages, and to the regulatory status of hydroquinone, which varies by jurisdiction (prescription-only in the EU and UK; over-the-counter at 2% in the US). The term is correctly spelled as one word with no hyphen. Do not confuse with 'kojic acid' or 'azelaic acid', which are alternative depigmenting agents with different mechanisms.
Usage
Usage note: Always verify concentration percentages and jurisdiction-specific regulatory status when editing clinical or consumer-facing copy.
In Context
- "A 4% hydroquinone cream was prescribed as part of the modified Kligman formula for recalcitrant melasma." — Prescription treatment plan
- "The article referenced over-the-counter hydroquinone at 4%, which is not legally available without prescription in the UK; the concentration should be queried with the author." — Proofreading note