SELECTION AND EVALUATION OF PROCESSING DATA

Drug A is a compressed tablet containing a single active ingredient. Inspection
of the batch record reveals that the following operations are involved in the
manufacture of the dosage unit. The active ingredient is combined with several
excipients in a twin-shell blender. The premix just prepared is granulated using
a purified water-binder solution. The resulting wet mix is milled using a specified
screen and machine setting, then dried using either an oven tray dryer or a
fluid bed dryer. When dry, the blend is oscillated, combined with previously
sized lubricant, and blended. The granulation is then compressed. See Figure 2
for a flow diagram of the manufacturing process.
At the premix blending step, the batch record provides two pieces of infor-mation: recommended blending time and blender load. The latter will be of little
interest, as only one size batch is produced for this product. Blender speed is
not specified in the batch record because it is fixed. Because mixing time has
been recognized as influencing blend uniformity, this operation will become the
first of the critical process steps for which we will want to collect historical
information [8].
The second major step is granulation. The process is controlled by the
operator, whose judgment is relied on for the appropriate end point. As no
information useful for process validation is available, we will move on to the
next step, comminution.
The batch record calls for passing the wet mix through a comminutor
using a no. 5 or 7 drilled stainless steel screen. Knife position and rotational
speed are two other factors that influence particle size; however, the step instruction
is quite specific about machine setup. Therefore, only screen size is a source
of variability for this step. We will want to know the frequency of use of each
screen.
Next, the granulation is dried to a target moisture of 1%. Either a tray or
fluid bed dryer may be used, at the discretion of area supervision. Regardless
of the method, drying time will be of interest. In addition, the final moisture
content should be ascertained for each batch. The dried granulation and lubricant
are then oscillated using a no. 10 or 12 wire screen. This is the last sizing
operation of the process; it will determine the particle size distribution of the
final blend. Knowing the history of use of each screen size is thus important.
The lubricant and granulation are blended for several minutes. The elapsed
mixing time is of interest because of its impact on drug distribution and the
generally deleterious effect of the lubricant on dissolution.
Because excess moisture is thought to have a negative effect on the dosage
form, loss on drying (LOD) is determined on the final blend.
Blending is followed by tableting. During compression, online measurements
such as tablet weight, hardness, and disintegration are made by the process
operator in order to ensure uniformity of the tablets. The weight of the
tablets is not measured individually; rather, the average weight of 10 tablets is
recorded. Although these data are good indicators of operation and machine
performance, we would prefer to have the more precise picture provided by
individual tablet weight.
Disintegration time and tablet hardness data could be collected from the
manufacturing batch records; however, for ease of administration these figures
will be obtained from the quality control test results, which also contain individual
tablet weighings.
Disintegration time was selected as a critical variable because for a drug
substance to be absorbed it must first disintegrate and then dissolve. The resistance
of a tablet to breakage, chipping, and so forth depends on its hardness.Disintegration, too, can be influenced by hardness of the tablet. For these reasons,
hardness testing results also will be examined.
Specifications used by quality control to release drug A are found in a
laboratory procedure. In addition to the previously discussed hardness and disintegration
time requirements, the procedure calls for determining the average
tablet weight by the United States Pharmacopeia (USP) procedure; that is, 20
individual tablets are weighed.
The control procedure also requires assay of individual tablets. Of all the
information available, these data will be the most useful in reaching an opinion
of the adequacy of the process to distribute the therapeutic agent uniformly.
In addition, the laboratory checks the moisture content of the bulk tablets.
It will be interesting to compare these results to the LOD of the final blend to
measure the contribution of material handling.