Influence of anatomical site and topical formulation on skin penetration of sunscreens.

Sunscreen products are widely used to protect the skin from sun-related damage. Previous studies have shown that some sunscreen chemicals are absorbed across the skin to the systemic circulation. The current study shows that absorption into the skin of sunscreen chemicals applied to the face is up to four times greater than that of the same product applied to the back.

Effect of lipophilic counter-ions on membrane diffusion of benzydamine.

Many topically applied drugs are ionized molecules that exhibit poor penetration across the lipid domains of the stratum corneum. Reduction of the charge on the molecule would be expected to enhance skin penetration. The objective of this study was to investigate the interaction of the non-steroidal anti-inflammatory drug benzydamine hydrochloride with suitable counter-ions including ibuprofen sodium.

Ion-pairs of ibuprofen: increased membrane diffusion.

The purpose of the present study was to determine the influence of pH and ion-pairing on the permeation of ibuprofen across polydimethylsiloxane (PDMS) membrane. The solubility of ibuprofen sodium was determined at a range of pH values. Saturated solutions were then used to determine the influence of pH on diffusion across PDMS as a model membrane.

Liquid chromatographic assay for common sunscreen agents: application to in vivo assessment of skin penetration and systemic absorption in human volunteers.

The purpose of the present study was to develop a reverse-phase high-performance liquid chromatographic (HPLC) assay for quantifying four common sunscreen agents, namely 2-hydroxy-4-methoxybenzophenone, 2-ethylhexyl-p-methoxycinnamate, 2-ethylhexylsalicylate (octylsalicylate) and salicylic acid 3,3,5-trimethcyclohexyl ester (homosalate) in a range of biological matrices. This assay was further applied to study the skin penetration and systemic absorption of sunscreen filters after topical application to human volunteers. Separation was achieved utilizing a Symmetry C(18) column with methanol-water as the mobile phase.