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Coating helps keep clinical trials 'blind'

05-Jul-2004

Boehringer Ingelheim has been granted a US patent on a way to disguise real and placebo tablets in a clinical trial - without having to resort to placing them in larger capsules which may be difficult for patients to swallow.

The technology covered in the patent can be used to obscure any indicating marks on a tablet using a sugar-based coating that does not have any impact on the stability of the drug, or its ability to be released from the tablet.

Clinical studies to determine the effectiveness of new drugs requires that identical tablets be prepared which contain an active drug, no drug (placebo) and/or a control drug. This is done in order to prevent the patients and investigators from knowing who is receiving the drug that is being tested.

When making dosage forms for a clinical trial, the active drug and the placebo are generally obscured using over-encapsulation, coating or de-branding. In other words, the tablet is placed in a larger capsule, coated with an obscuring layer or 'de-branded' using a de-inking agent.

The patent claims over-encapsulation is effective but time consuming. Moreover, strict quality controls are required to assure that the capsule and tablet are bioequivalent and are manufactured properly, and the gelatin and moisture in the capsules may introduce stability problems.

Meanwhile, overcoating of tablets has not been successful for embossed tablets because of the formation of ghost images in the areas where the tablets are embossed, according to the patent. And the de-branding of printed tablets and capsules is a labour intensive process that may also raise the question of stability, due to the use of solvents for manually de-inking the printed matter on the dosage form.

These problems could mean that companies have to carry out stability and bioequivalence studies on the dosage form, hiking the expense of the trial.

Another alternative is that tablets can be milled and filled into capsules, although this is not always suitable for complex formulations and raises issues about how closely the resulting dosage form matches its parent in uniformity, stability and bioavailability.

Boehringer's solution is to coat the tablets with a polymer such as polyethylene glycol, and then progressively bind sugar-based coatings to this layer until the tablet is 'rounded-out', and any embossed areas are filled.

The invention also provides a method for coating micro tablets for the purpose of rounding them to facilitate the mechanical filling of the micro tablets into capsules.

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