A thin layer of Benoquin Cream 20% should be applied and rubbed into the pigmented area two or three times daily, or as directed by physician. Prolonged exposure to sunlight should be avoided during treatment with Benoquin Cream 20%, or a sunscreen should be used.

Cell viability was measured by MTT assays according to manufacturer’s instructions. In brief, 20,000 cells per well were plated in triplicate wells of a 96-well plate to attach overnight. Cells were either treated with vehicle alone or with 250 or 500 mM of Monobenzone (MBEH) for 24 hours. MBEH (Sigma) was dissolved in 20% dimethyl sulfoxide and mixed with 70% ethanol for a stock concentration of 250mM. The use of a vehicle control refers to the use of 20% dimethyl sulfoxide in 70% ethanol. MTT reagent (tetrazole) was added to the cells and incubated in a 371C humidified chamber for 4 hours. Tetrazole is converted to formazan in the mitochondria of living cells. The formazan crystals formed were dissolved in solubilization buffer and the absorbance was read in a spectrophotometer at a wavelength of 562nm (BMG Labtech, Durham, NC). Cell viability was calculated as a percentage of absorbance of the samples relative to untreated control. Treatment with MBEH caused dose-dependend cell death.