THE PERCUTANEOUS ABSORPTION OF SALICYLIC ACID

Quantifying Skin Uptake of Topicals After 1,927-nm and 1,440-nm Nonablative Fractional Diode Laser Treatment

BACKGROUND

Although the stratum corneum limits transdermal absorption of topicals, laser devices can enhance topical uptake by disrupting the skin barrier. Nonablative lasers are commonly used, but their effects on topical uptake should be quantified to optimize outcomes.

OBJECTIVE

The objective of this study is to analyze transdermal uptake of 4 topicals after nonablative fractional diode laser pretreatment.

METHODS AND MATERIALS

Human donor tissue was pretreated ex vivo with a nonablative fractional diode laser (1,927 nm or 1,440 nm, at varying treatment densities, powers, and peak energies) followed by application of either 2% salicylic acid, 10% ascorbic acid, over-the-counter mineral eye serum, or 4% hydroquinone. Topical uptake was quantified over 24 hours.

RESULTS

Despite lower power settings, pretreatment with the 1,927 nm wavelength was associated with greater uptake of 10% ascorbic acid, mineral eye serum, and 4% hydroquinone than the 1,440 nm wavelength. In addition, 1,440-nm laser pretreatment with higher density (320 microscopic treatment zones [MTZ]/cm2) and peak power (3 W) was associated with similar uptake but greater retention of 2% salicylic acid and greater uptake of 10% ascorbic acid than that with lower density (80 MTZ/cm2) and peak power (1.2 W).

CONCLUSION

When using laser pretreatment, device settings should be adjusted to balance outcomes with potential side effects.

THE PERCUTANEOUS ABSORPTION OF SALICYLIC ACID

The present paper reports on the penetration of salicylic acid, a substance with high permeability, through swine skin. Liquid scintillation counter and autoradiographic measurements were performed, on the excised swine skin to which ointment had been applied. The results indicated that the substance penetrated mainly through transfollicular route and was deposited transiently at various levels of each follicle, resulting in zig-zag pattern on the liquid scintillation counter curve. The autoradiographic study also revealed a heavy transfollicular pattern of the substance though a slight transepidermal pattern was also noted. Whether the substance penetrates because of its lipid solubility or because of its affinity to the keratinous tissue is still open to question.