Interactions between cyclodextrins and pilocarpine - As an example of a hydrophilic drug

Investigations of interactions between cyclodextrins (CyDs) and pilocarpine (P) were carried out by means of several common methods. Subjects of interest were aqueous solutions and solid dispersions of the drug and various cyclodextrins. The solid dispersions were prepared by spray-drying and by lyophilization of the aqueous solutions. These products and the equivalent physical mixtures were compared by scanning electron microscopy (SEM), differential thermal analysis (DTA), powder X-ray diffractometry (XRD) and Fourier transformation infrared (FTIR) spectroscopy. Methods for investigations of the aqueous solutions were H-1-NMR,C-13-NMR, correlation, rotating frame Overhauser effect and nuclear Overhauser effect spectroscopy, reversed phase high performance liquid chromatography (HPLC), UV-spectroscopy and conductometry. The results obtained may be interpreted as an inclusion of pilocarpine in cyclodextrins. In vitro and in vivo studies yielded results of a modified release and a slightly higher bioavailability of pilocarpine in the presence of the tested cyclodextrins. Therefore we assume that the use of cyclodextrins in ophthalmic preparations could be advantageous not only for lipophilic drugs but also for hydrophilic drugs.