Medicament Release From Ointment Bases: V. Naproxen In-Vitro Release and In-Vivo Percutaneous Absorption In Rabbits

The in- vitro release of Naproxen from various ointment bases, including a water-washable base with the drug in the water phase (I) and the drug in the oil phase (II), a hydrophilic base with the drug in the water phase (III), and the drug in the oil phase (IV), and an anhydrous ointment (V), a gel (VI) and a modified University of California (U .C .H.) base (VII) were studied. In addition, the effects of various additives (urea, ethanol, dimethyl sulfoxide and polyethylene glycol-400) on the release of Naproxen from formulations (I) and (II) were determined. Low concentrations of urea and ethanol in the formulations increased the release of the drug from both these bases, however, higher concentrations adversely affected the release of the drug. While dimethyl sulfoxide (DMSO) had no significant effect on the drug release, the inclusion of polyethylene glycol-400 in both bases decreased the release of Naproxen.

The percutaneous absorption of Naproxen from the waterwashable base (drug in the oil phase) and hydrophilic base (drug in the oil phase) were studied by applying the ointments on rabbit's skin. It was observed that the bioavailability of Naproxen from the hydrophilic base was slightly greater than that from the water-washable base, and that DMSO had no effect in enhancing the in-vivo release of Naproxen from the ointments evaluated. Using the in-vivo data, the absorption and elimination rate constants, the half-life and AUC were calculated.