FTIR spectroscopic studies were performed to find out the pos-sible interaction and complex formation between PR and lipidduring the preparation of the NLC. The FTIR spectrum (Fig. 7) of thepure PR revealed the absorption bands at 3381 cm−1(hydrate O Hstretching), 3018 cm−1(aromatic C H stretching), and 1620 cm−1(aromatic C C stretching). These were the characteristic peaks ofPR and these characteristic peaks were only present in the PR-lipid melt except the pure PR. FTIR spectra of the blank NLC and the PR-NLC were almost the same. In the FTIR spectrum of PR-NLC, peaks corresponding to PR disappeared or were buried in thepeaks of blank NLC indicating PR entrapment in lipid matrix. Sim-ilar result was also observed for other drugs [37–39]. This couldbe explained by drug-enriched core model for the incorporation ofactive compounds into SLN [5]. Similar to the SLN, the PR may startprecipitating first due to its high melting point as core and the lipid(solid lipid and liquid oil) may form the coating around the core.