Effect of Surfactants on the Crystal Properties and Dissolution Behavior of Aspirin

The aim of present investigation was to evaluate the effects of different surfactants on crystal properties and dissolution behavior of aspirin. Aspirin was crystallized through methanol in the presence of three surfactants namely cetrimide (cationic), sodium lauryl sulphate (anionic) and Tween 80 (non-ionic). All the three surfactants were used in various concentrations ranging from 0.0001M to 0.1M. The crystals were characterized for habit, melting points, bulk density, true density, solubility and drug-surfactant interaction studies using infra-red spectroscopy. Dissolution profile of aspirin tablets prepared with surfactant was compared with control aspirin tablets using USP dissolution apparatus. The concentration and charge of the surfactants have brought about modifications in the crystal habit of aspirin, which has subsequently affected the crystal properties such as density and equilibrium solubility. IR spectroscopic studies revealed that the internal lattice structure of aspirin was not altered in presence of the surfactants in all of the employed concentrations. However, presence of surfactants considerably modified crystal habit and other crystal properties. Such changes apparently appeared to be responsible for altered equilibrium solubility. Presence of surfactant (0.1 M SLS) in aspirin tablets enhanced the dissolution of aspirin significantly as compared to control aspirin tablets (P<0.05). From these results it can be concluded that the choice of selection of surfactants and optimization of its concentration is important in manufacturing of dosage forms with aspirin.