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•Article: 35 Years Of Flow-Through Cell Dissolution

By SOTAX Corporation

From the first conceptual drawings from the creator of the flow through method, Dr Langenbucher at Ciba in the early seventies to the latest development for elution testing of drug eluting stents and injectables, the flow-through cell has always been the dissolution instrument of choice for novel dosage forms due to its flexibility and has evolved with the evolution of new drug delivery technologies.

Originally designed for poorly soluble compounds where more than the compendial USP 1, 2 and 3 media volumes could provide, the flow-through cell system has always been linked to "optimal sink conditions" allowing for complete flexibility in terms of media volume. In the "Open Loop" configuration, fresh media crosses the dosage form. The total amount of media is determined by the flow rate used. It is therefore more appropriate to link the FTC technique to the "sink conditions" in which the concentration of solute is from 5 to 10 times higher than the saturation concentration. In an "Open Loop" configuration, the total media volume is infinite. With the evolution of low dose products, it is also possible to use the same flow cell to work with a fixed volume of media in a "Closed Loop" configuration. In a "Closed Loop" set up, media is re-circulated across the dosage form. Media volumes in this set up can be as low as 10 ml (small volume dissolution) and as high as needed. It is now possible to compare 250 ml, 500 ml, 900 ml, 1 l, 2 l paddle, baskets and BioDiss methods to the FTC method. The FTC method provides advantages over the USP methods such as different hydrodynamic and mixing effects as well as eliminates the coning or dead zones effects seen in USP 1 and 2.

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•Article: 35 Years Of Flow-Through Cell Dissolution