Pharmaceutical evaluation of steroidal ointments by ATR-IR chemical imaging: distribution of active and inactive...

We recently used micro attenuated total reflection infrared (ATR-IR) spectroscopy to conduct imaging analysis of ointments and evaluate the distributions of the active pharmaceutical ingredient (API) and excipients. An alclometasone dipropionate (ALC) ointment was used as a model product. Almeta, a brand-name product, had a domain with absorbance at 1656 cm(-1) attributable to the carbonyl group of ALC, the API. Absorbances at 1040 and 3300 cm(-1) were also noted in this domain, indicating the presence of the solubilizer, propylene glycol. Data also suggested the presence of benzyl alcohol in this domain. More detailed analysis showed the distribution of surfactants and other excipients in the base. Similar results were obtained for Vitra, a generic version of Almeta. Imaging analysis with micro ATR-IR confirmed that both ointments are liquid droplet dispersions with ALC dissolved in propylene glycol and dispersed in a base. However, minor differences in the ingredient distributions of the two ointments were detected and reflect differences in excipient concentrations and type, or manufacturing differences. In summary, we used micro ATR-IR for imaging analysis of an original ointment, Almeta, and its generic form Vitra, and established a method for visually evaluating the distributions of the API and excipients in these ointments.