Deconvolution of the CPMAS C spectrum of amorphous IND by Yuan et al. showed, that besides the aforementioned conformations, free carboxylic acid and hydrogen bonded carboxylic acid chain conformations are present as well. The spectrum of P1 shows broad signals with one prominent peak at 172 ppm (signal 4 in This indicates that the H-bonding capacity of P1 with IND is somewhat saturated at this point, leading to the formation of IND carboxylic acid dimers. Similarly, signal 2 is not observed below a drug loading of 50wt% but appears as a shoulder at lower ppm values (172 ppm) above 50wt%, with its intensity increasing with increasing drug loading.