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Ultrasonic approach for viscoelastic and microstructure characterization of granular pharmaceutical tablets.

International journal of pharmaceutics (2013-07-04)
Armin Saeedi Vahdat, Chaitanya Krishna Prasad Vallabh, Bruno C Hancock, Cetin Cetinkaya
ABSTRACT

The mechanical properties of a solid dosage, defined by its granular micro-structure and geometry, play a key role in its dissolution profile and performance. An ultrasonic method for extracting the viscoelastic material properties and granular structure of drug tablet compacts is introduced and its utility is demonstrated for tablet compacts made of microcrystalline cellulose (MCC), lactose monohydrate, and sodium starch glycolate as well as magnesium stearate as lubricant. The approach is based on the effect of viscoelasticity and internal micro-structures on the frequency-dependent attenuation of an ultrasonic wave propagating in a granular medium. The models for viscoelastic (a two-parameter Zener model) and scattering attenuation (Rayleigh model) mechanisms are employed. The material parameters including viscoelastic and scattering parameters (average Young's modulus, stress and strain relaxation time constants, and the Rayleigh scattering material parameter) and grain size distribution with a known distribution profile are extracted by an optimization algorithm based on the least square method. The results also indicate good agreement between experimentally and computationally determined phase and group velocities in compacted samples. It is found that the effects of both attenuation mechanisms are present and the extracted grain size distribution parameters are in good agreement with the optically determined values.

MATERIALS
Product Number
Brand
Product Description

USP
Sodium Starch Glycolate Type A, United States Pharmacopeia (USP) Reference Standard
Sigma-Aldrich
Lactose, tested according to Ph. Eur.
Supelco
Stearic acid, analytical standard
Supelco
Lactose, Anhydrous, Pharmaceutical Secondary Standard; Certified Reference Material
Supelco
Stearic acid, certified reference material, TraceCERT®
Sigma-Aldrich
Stearic acid, Vetec, reagent grade, 94%
Sigma-Aldrich
Stearic acid, ≥95%, FCC, FG
Sigma-Aldrich
Stearic acid, reagent grade, 95%
Supelco
Stearic Acid, Pharmaceutical Secondary Standard; Certified Reference Material
Lactose (anhydrous), European Pharmacopoeia (EP) Reference Standard
Stearic acid, European Pharmacopoeia (EP) Reference Standard
Sigma-Aldrich
Stearic acid, Grade I, ≥98.5% (capillary GC)