(180ca) Solvent Penetration Rate in Tablet Measurement Using Video Image Processing

Solvent Penetration Rate in Tablet Measurement Using Video
Image Processing

Purpose

The
performance of drug delivery systems, such as pharmaceutical tablets, is usually
quantified by the dissolution rates required to maintain the desired active
ingredients concentration in the gastrointestinal tract.  Whether or not the tablet matrix
disintegrates, the rate at which solvent penetrates the matrix can be highly
influential in terms of the drug release rate as well as the total drug
released.  Therefore, experimental
measurements of the velocity of the liquid front are needed in order to adjust or optimize the product performance. In addition,
such measurements can help us understand the diffusion mechanism for a
particular solvent - tablet matrix combination. 
We seek to validate a low cost method for determination of solvent
penetration in tablets and evaluate the performance of numerical modeling of
this penetration.

Methods

Tablet
composed of spray dried lactose are manually compressed to produce samples with
equivalent pore structures.  Solvent is
then deposited atop sample tablets and the process of solvent penetration into
the matrix is recorded using a GimaGo GO443C camera.  Using OPENCV, the videos are processed such
that the solvent fronts are isolated and their progress tracked.  The process is repeated for tablets made of a
pharmaceutical blend.  The resulting
progress of the solvent through the polymer matrices are compared to the
Washburn and molecular sorption models.

Results

Solvent front
propagation as captured by the video processing technique shows the effective
fit of the system to the Washburn and molecular sorption models to tablets of
pure lactose as shown in Figure 1a.    

Figure 1: Model fits for (a)lactose
tablets,   tablets of low (b) and high (c) total strain blends.

Figure 1 b
and c shows the evolution of the solvent front and associated models in tablets
made from model pharmaceutical blends.

Conclusions

We have
presented an experimental technique for the measurement of the solvent/water
penetration in immediate release tablets using digital video image processing
which may be useful if many tablets have to be processed and their absorption
ability compared.  The solvent
penetration results of a simple system fit well with the molecular sorption
model proposed by Vesely, however, the lack of direct correlation of the
coefficients with actual physical parameters limits the insights which can be
gleaned from this model.  The more
complex systems produce more variable results. 
For tablets made from more complex powder blends, the mechanisms
governing penetration are not completely incorporated in either model utilized
herein.