About hydroquinonebenzenediol derivative, depigmenting agent.mechanism of action of hydroquinonehydroquinone decreases the formation of melanin in the skin. it inhibits tyrosinase and other melanin forming enzymes and thus decreases the formation and increases the degradation of melanosomes.indications for hydroquinone1. melasma 2. freckles 3. hyperpigmention 4. lentigo special precautions while taking hydroquinone1. discontinue the drug if skin irritation occurs 2. care should be taken to avoid it`s entry to eyes, nose, lips or mouth 3. avoid exposure to sunlight 4. use a sunscreen and wear protective clothing when exposure to the sun 5. do not use hydroquinone topical on burned, dry, chapped, or irritated skin, or on an open wound. it could make these conditions worse 6. hepatic impairment 7. renal impairment 8. along with other topical medication on the same area