Melting Diagrams of Adefovir Dipivoxil and Dicarboxylic Acids: An Approach to Assess Cocrystal Compositions

Enhanced Dissolution of Naproxen by Combining Cocrystallization and Eutectic Formation

Improving dissolution properties of active pharmaceutical ingredients (APIs) is a critical step in drug development with the increasing occurrence of sparingly soluble APIs. Cocrystal formation is one of the methods to alter the physicochemical properties of APIs, but its dissolution behavior in biorelevant media has been scrutinized only in recent years. We investigated the combined strategy of cocrystallization and eutectic formation in this regard and utilized the cocrystal model system of naproxen and three pyridinecarboxamide isomers. Binary melting diagrams were constructed to discover the eutectic compositions of the three cocrystals with excess amounts of pyridinecarboxamides. The melt-crystallized eutectics and cocrystals were compared in their dissolution behaviors with respect to neat naproxen. The eutectics enhanced the early dissolution rates of the cocrystals in both the absence and presence of biologically relevant bile salt and phospholipid components, whereas the cocrystal dissolution was expedited and delayed, respectively. The combined strategy in the present study will be advantageous in maximizing the utility of the pharmaceutical cocrystals.

A Comprehensive Study of a New 1.75 Hydrate of Ciprofloxacin Salicylate: SCXRD Structure Determination, Solid Characterization, Water Stability, Solubility, and Dissolution Study

One problem that often arises during the formulation of a dosage form is the solubility and dissolution of the active ingredients. This problem arises in ciprofloxacin, which is a BCS class IV fluoroquinolone antibiotic. A pseudopolymorph is a kind of polymorph in which the number of hydrates is different. In this study, a new pseudopolymorph comprised of ciprofloxacin and salicylic acid was found, namely the salt ciprofloxacin salicylate 1.75 hydrate form. This new solid phase was analyzed by Fourier-transform infrared spectroscope (FTIR), Raman spectroscopy, and thermal analysis and proven by Powder X-ray Diffractometry (PXRD) analysis. The crystal structure was successfully determined by Single Crystal X-ray Diffractometry (SCXRD) analysis. It was found that the piperazinyl group of ciprofloxacin is protonated by H+ from the carboxylic group of salicylic acid. In the unit cell, two ciprofloxacin and two salicylic acid molecules were independent with four water molecules, in which one water molecule had 0.5 occupancy due to inversion symmetry. Interestingly, this hydrate crystal dehydrated by grinding for 105 minutes forms an anhydrous crystalline phase, which was analyzed with FTIR, Raman spectroscopy, thermal analysis, and PXRD. The solubility and dissolution tests were carried out using UV-Visible spectrophotometry and a multiple linear regression method. This new hydrate solid phase has a better profile than the original ciprofloxacin crystal, according to the solubility and dissolution tests.