Possible enhancing mechanism of the cutaneous permeation of 4-biphenylylacetic acid by β-cyclodextrin derivatives in hydrophilic ointment

Abstract

The enhancing effects of heptakis(2,6-di-O-methyl)-β-cyclodextrin (DM-β-CyD) and 2-hydroxypropyl-β-cyclodextrin (HP-β-CyD) on the percutaneous absorption of 4-biphenylylacetic acid (BPAA), a nonsteroidal anti-inflammatory drug, in hydrophilic ointment were studied and compared with the parent β-cyclodextrin (β-CyD). 13C-NMR measurements suggested that the biphenyl group of BPAA is preferably included within the cavity of three β-CyDs. The three β-CyDs remarkably enhanced the release of BPAA from the hydrophilic ointment base and the in vitro cutaneous permeation, depending on the increase in solubility of BPAA in the ointment base, Pretreatment of the ointment containing DM-β-CyD or HP-β-CyD onto the isolated skin of hairless mice, however, provided no effects on the skin permeation of BPAA. When propylene glycol was used as a vehicle, both the release rate and cutaneous permeation parameters showed no appreciable difference between BPAA alone and its HP-β-CyD complex, because the solubilities of BPAA and its HP-β-CyD complex were almost comparable in the vehicle. The present results suggested that the enhancing effect of β-CyDs on the percutaneous absorption of BPAA can be mainly ascribed to an increase in the solubility of BPAA in the hydrophilic ointment.