Table 2.

Methods of characterization of pharmaceutical powder before and during the compression process: direct and indirect methods.

	Method of Evaluation	Type of Method	Characterization	Reference(s)
DIRECT METHOD	Microscopic Evaluation	Scanning Electron Microscopy	Morphology and surface characteristic of particles and pellets	[79]
	Particle Size Analysis	Sieve Analysis	Size of the particles and pellets of pharmaceutical compounds	[80]
INDIRECT METHOD	Analytical Procedures	Dissolution Studies (In Vitro)	Release profile(s) of active pharmaceutical ingredients	[81]
	Texture Analysis	Texture Analyser	♦Elastic–plastic properties of powders and pellets. ♦Disintegration of compacts of fast-dissolving formulation ♦Mucoadhesion properties of polymers	[82]
	Compression Analysis	Heckle Model	♦Powder compressibility–porosity relationship ♦Elastic–plastic deformation (Figure 5)	[83]
	Compression Analysis	Kawakita Equation	♦Flowability and cohesiveness of bulk powder ♦Volume–compressibility relationship (Figure 6) ♦Powder rearrangement at low pressure	[84]
	Compression Analysis	Partial Differential Equations	♦Prediction and evaluation of the variables influencing mechanical properties ♦Determine shape model of pharmaceutical tablets	[85]
	Numerical Compression Analysis	Finite Element Method	♦Evaluation of tablets shape and their mechanical properties	[86]