Describe the different theories of drug dissolution. State the Noyes Whitney Equation and explain all the terms of the stated equation.
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Dissolution Theory
ã Copyright 2011 by Alex Avdeef. All rights reserved.
This section is a rigorous theoretical discussion of the state-of-the-art data analysis used for interpreting pH-dependent dissolution processes exhibited by poorly-soluble multiprotic ionizable test compounds synthesized by medicinal chemists in pharmaceutical companies.1-5 This data analysis is encoded in the µDISS-X software from in‑ADME Research.
This can be of interest to candidate-selection analytical/physical chemists intent on designing information-rich dissolution measurements, and on effectively communicating these results tomedicinal chemists, so that rational structural modifications leading to improved physicochemical properties can be made. Also, this can be of interest to preformulation scientists, charged downstream with the daunting task of formulating very insoluble molecules into drug products.
The enhanced theory of dissolution kinetics is spotlighted with the convective diffusion &simultaneous chemical reaction (CDR) model, incorporating the low-ionic-strength Vinograd-McBain6 electric field treatment. The new computational treatment described here extends the generality and robustness of the CDR model, clarifies limitations in earlier underlying assumptions, and aspires to provide some of the finishing touches to the pioneering works of Higuchi et al.,15,16 Mooney et al.,17-20 McNamara et al.,21-23 and Southard et al.,24 and a number of others.
The coverage here is focused on two applications of CDR data analysis: (a) rotating disk intrinsic dissolution rate (disk-IDR)25 and (b) Wang-Flanagan 7,8 spherical particle model (particle-IDR)models. The rigorous CDR kinetics model may be most helpful in early applications of IDR, where compounds are studied as compacted solid rotating disks or suspended powders of the pure compound. Such investigations are done long before the traditional formulation development and quality control type of applications.
Concentration-time profiles as a function of pH, buffers, salt, complexation and self-aggregation are considered. Concentration-position profiles of all species in the aqueous boundary layer (ABL), including solid species, are also considered under the above conditions. The new small-volume (≥ 1 mL) dip-probe UV detection apparatus, developed by pION INC for polymorph transformation/salt selection/solubility screening, is discussed using published case studies.9-14
ã Copyright 2011 by Alex Avdeef. All rights reserved.
This section is a rigorous theoretical discussion of the state-of-the-art data analysis used for interpreting pH-dependent dissolution processes exhibited by poorly-soluble multiprotic ionizable test compounds synthesized by medicinal chemists in pharmaceutical companies.1-5 This data analysis is encoded in the µDISS-X software from in‑ADME Research.
This can be of interest to candidate-selection analytical/physical chemists intent on designing information-rich dissolution measurements, and on effectively communicating these results tomedicinal chemists, so that rational structural modifications leading to improved physicochemical properties can be made. Also, this can be of interest to preformulation scientists, charged downstream with the daunting task of formulating very insoluble molecules into drug products.
The enhanced theory of dissolution kinetics is spotlighted with the convective diffusion &simultaneous chemical reaction (CDR) model, incorporating the low-ionic-strength Vinograd-McBain6 electric field treatment. The new computational treatment described here extends the generality and robustness of the CDR model, clarifies limitations in earlier underlying assumptions, and aspires to provide some of the finishing touches to the pioneering works of Higuchi et al.,15,16 Mooney et al.,17-20 McNamara et al.,21-23 and Southard et al.,24 and a number of others.
The coverage here is focused on two applications of CDR data analysis: (a) rotating disk intrinsic dissolution rate (disk-IDR)25 and (b) Wang-Flanagan 7,8 spherical particle model (particle-IDR)models. The rigorous CDR kinetics model may be most helpful in early applications of IDR, where compounds are studied as compacted solid rotating disks or suspended powders of the pure compound. Such investigations are done long before the traditional formulation development and quality control type of applications.
Concentration-time profiles as a function of pH, buffers, salt, complexation and self-aggregation are considered. Concentration-position profiles of all species in the aqueous boundary layer (ABL), including solid species, are also considered under the above conditions. The new small-volume (≥ 1 mL) dip-probe UV detection apparatus, developed by pION INC for polymorph transformation/salt selection/solubility screening, is discussed using published case studies.9-14
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