Table 6.

Terms of active research clusters with time from co-citation analysis.

Categories	Year
	~1980	1980~1996	1997~2003	2004~2010
Model drug	Diflunisal, diazepam	sulfathiazole, paracetamol, zolpidem, glucosamine	sibutramine, tranilast, megestrol acetate	felodipine, kinetisola, itraconazole, ketoprofen, glibenclamide
Carrier	polyethlene glycol 6000, amphiphilicity	sodium lauryl sulfate, hydroxypropyl methylcellulose, eudragit, cellulose derivative matrice, lactose, polyethlene glycol, povidone-sodium, cholate-phospholipid mixed micelle	N/A	Polyvinylpyrrolidone
Preparation method	N/A	spray	supercritical fluid	fusion production, hot-melt extruded, supercritical antisolvent process
Characterizations	N/A	N/A	N/A	thermoanalytical measurement, NMR atomic force microscopy
Mechanism	N/A	amorphous drug stabilization, sustained-release, thermal behavior, dissolution behaviour	crystalline property, solid nano dispersion system	binary dispersion, quantifying drug crystallinity, in vivo drug absorption, drug-release properties, ab initio polymer selection, physical stability studies, acidic decomposition characteristic, free amorphous solid dispersion, glassy form, drug-carrier interaction, heterogeneity, excipient distribution, phase diagram, enthalpy relaxation studies, crystal engineering principle, moisture, miscibility