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Pharmaceutical Manufacturing and Packing Sourcer

WeightWatchers

During the manufacture of dry powder inhalers (DPIs) it is necessary to ensure that the filling process puts the right weight or volume of powder into each pocket. The DPI product consists of a metal foil into which small pockets are pressed. Fine powder with a granular size of between 50 and 100 microns is placed into each pocket in a filling process and then a sealing foil lid is placed over the top to contain it. Once a user receives the product, contained in a plastic carrier, the powder carrying the drug is inhaled by exposing the pocket to the atmosphere, usually by peeling the lid back inside the plastic carrier.

It is important that the right quantity of powder is inhaled so that the user gets the right dose each time the product is used. In order to make sure that the user gets the right dose, each batch of powder is checked for consistency before being placed into the pockets. Following this, the weight of the powder in each pocket is checked to make sure that each pocket contains the same amount. It is possible to measure the volume of powder, but this is hard to do accurately as the volume can vary depending on the compression of the powder into the pocket due to the fact that the powder is fairly compressible. As such, volume is regarded as a poor indicator of dose. As a quality control check, performing a weighing operation at regular stages in the production process ensures that the dose in each pocket is within specification.

CHECKWEIGHING ALTERNATIVES

There are a number of basic methods of weighing the powder in each pocket. One is to pour the pocket content out into a suitable vessel and then weigh the content. This has the advantage of weighing exactly what you want to weigh. This approach assumes that all the powder falls out of the pocket – and from manual experimentation this was found not to be the case. Some powder formulations are slightly sticky so that some powder remains on the foil, both on the lid and in the pocket. When the user inhales using the plastic carrier, the air flow generated by the user helps the powder leave the pocket.


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James Aitken initially qualified with a Mechanical Engineering degree, obtaining a first from Loughborough University in 1975, before completing an MSc in Computation at UMIST in 1977. His company Aitken Scientific Ltd was set up in 1982 to provide software development services to science and engineering related companies, thus combining his interests in software with engineering applications. James has been involved with CheckWeighing systems for over six years, and has been developing systems to GAMP standards for pharmaceutical production.
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James Aitken
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