Investigation of drug release from suspension using FTIR-ATR technique: part II. Determination of dissolution coefficient of drugs

Imaging Analysis Enables Differentiation of the Distribution of Pharmaceutical Ingredients in Tacrolimus Ointments

We demonstrated the difference in the distribution state of pharmaceutical ingredients between tacrolimus (TCR) original ointment and six kinds of generic medicines. Two-dimensional imaging and depth analysis using attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopy and confocal Raman microscopy were used, in addition to the evaluation of pharmaceutical properties, including spreading properties, rheological properties, and amount of solvent. The solvents, such as propylene carbonate and triacetin, in TCR ointments formed liquid droplets and dispersed in hydrocarbon oils. Waxes, white beeswax and beeswax, formed other domains. Confocal Raman microscopy could detect liquid droplet size without coalescence of that on germanium or glass surfaces. The combination of ATR FT-IR and confocal Raman imaging would be a powerful tool to reveal the size and shape of liquid droplets of pharmaceutical ingredients in semisolid formulations.

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

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.

Pharmaceutical applications of Mid-IR and Raman spectroscopy

Mid-IR and Raman spectroscopy are versatile tools in pharmaceutics and biopharmaceutics, with a wide field of applications ranging from characterization of drug formulations to elucidation of kinetic processes in drug delivery. After an introduction to the basic principles of IR and Raman spectroscopy, new developments in applications of these methods for studying drug delivery systems, in particular topical drug delivery, will be reviewed. FTIR-ATR is a well-established standard method used to study drug release in semisolid formulations, drug penetration, and influence of penetration modifiers; it is also capable of in vivo studies. FTIR-PAS has been applied to measure drug content in semisolid and solid formulations, to determine drug penetration into artificial and biological membranes. The big advantage of this technique is the possibility of spectral depth profiling. However, FTIR-PAS is so far limited to in vitro investigations. Raman spectroscopy can be used to characterize the structure of colloidal drug carrier systems. Raman spectroscopy is readily applicable to in vivo studies, but such investigations must fulfill the relevant laser safety guideline. Recently, there has been tremendous technical improvement in vibrational microspectroscopy. FTIR imaging shows great promise in its ability to visualize the drug and excipient distribution in pharmaceutical formulations such as tablets and therapeutic transdermal systems, as well as to reveal the mechanism of drug release. Furthermore, this unique technique offers completely new possibilities to study the lateral diffusion of drugs.

Spectroscopy of polymer/drug formulations processed with supercritical fluids: in situ ATR-IR and Raman study of impregnation of ibuprofen into PVP

In situ ATR (attenuated total reflectance)-IR spectroscopy has been used to study poly(vinylpyrrolidone) (PVP) films subjected to a solution of ibuprofen in supercritical CO2. The process of impregnation of ibuprofen into PVP has been monitored in situ. It has been shown that the supercritical fluid impregnation process results in ibuprofen being molecularly dispersed in a polymer matrix with ibuprofen molecules interacting with the C=O group of PVP. Raman spectra of ibuprofen impregnated into PVP from supercritical fluid solution have also been measured and compared with the Raman spectra of crystalline ibuprofen. ATR-IR spectroscopy has also revealed specific interactions between the C=O groups of PVP and CO2. Impregnation of ibuprofen into PVP makes the C=O groups of PVP less available for interactions with CO2. It has also been demonstrated that the presence of ibuprofen in PVP also affects sorption of water into PVP.