The first in situ analyses of dosage form changes during drug release involved CARS. Kang et al. imaged the distribu on and release of paclitaxel from poly(ethyl-co-vinyl acetate) films in an isoporopyl alcoholphosphate buffered saline solu on . CARS has also been used to image theophylline anhydrate release from lipid extrudates in water, as well as simultaneous theophylline monohydrate forma on . More recently, SRS microscopy has been used to image poly(D,L-lac c acid) extrudates as model implant formula ons, in which par cles of the API, entecavir, were distributed. SRS was employed to image the distribu on of the two components, as well as the decrease in size and eventual disappearance of individual API par cles during drug release in a flow through cell .