DRUG DISCOVERY AND DEVELOPMENT 51
Controlling your weight E
A new solution sets out to improve the process by which correct tablet weights are maintained in a tablet press. By Jutta Hartmann.
nsuring the correct tablet weight is the top priority when compressing tablets for pharmaceutical application.
To ensure that the tablet weight is always within the prescribed limits, modern tablet presses apply a constant compression force control. Tis ensures that the powder dosing is adjusted to maintain the tablet target weight if needed. In addition, tablets that are outside the individual limits for compression force and hence weight, are identified and rejected.
“In-line tablet weight measuring provides the highest possible precision and continuity of the tablet weight even when there are variations in the bulk density.”
However, compression force control can usually not determine a weight drift due to a variation in bulk density, as it can occur during the processing of a large volume batch, as well as temperature drifts of the tableting equipment and tablet tooling.
Here, an automatic check- weighing device or IPC is used to sample tablets from good production of the press at regular intervals, which are then checked off-line for weight and other parameters.
Te traditional offline sample sequence is 20 tablets every 20 minutes, of which typically 10 tablets are evaluated for their weight. If a weight drift is detected, the IPC will give feedback to the tablet press, in order to trigger a weight adjustment.
Tis procedure raises two questions. What happens within the 20 minutes it takes to process a tablet sample? And is it really necessary to take tablet samples, which are later discarded?
A newly developed system is aiming to address both of those questions and in doing so, bring
Fig. 1 The new solution is designed to allow tablets to be tested while they are in the production line.
great improvements to the entire process.
CWC (continuous weight control) is a new system to measure the weight of the produced tablets in-line in the tablet chute, without destroying them.
During tablet production, selected tablets are fed into the CWC from the good production channel of the press. Tey are then checked for weight and (if found to be OK) released as good product.
After 10 weighing operations, the average weight of the evaluated
10 tablets is compared to the set weight specifications and corrective feedback is triggered if necessary.
Te weight measurement can be performed on tablets from individual punches per revolution or from a random sequence of punches.
Te system is integrated into the machine control system and measuring results can be used directly for machine regulation/ adjustment.
After the weighing process the tablet is returned into the good channel of the tablet chute.
www.scientistlive.com
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