Increased flexibility when coating highly potent solid dosage forms

The demand for highly potent oral solid dosage (OSD) forms is increasing, as is the need for corresponding processing options, which prompted Syntegon to augment its existing portfolio with the Sepion drum coater, explains Product Manager Fritz-Martin Scholz

The new products are designed for closed material handling with batch sizes of 10–100% of the drum volume. The automatically adjustable spray arm and significant process optimisations, including containment options, ensure an optimal coating process.

Tablet coating is a demanding and important process step in tablet production. Only a precise and tailor-made coating solution meets both the colouring and taste-masking needs of many applications, not to mention more demanding requirements such as enteric coatings, controlled release coatings or the addition of an active ingredient.

For Syntegon (formerly Bosch Packaging Technology), it was an obvious decision to complement the cutting-edge high-shear mixer-granulators and fluid bed systems of the Hüttlin product brand with a state-of-the-art drum coater.

Syntegon has combined decades of experience derived from the former Manesty product brand with the expertise of Hüttlin in tablet coating and process technology to offer customers an ideal fusion of know-how and innovation.

Key requirements

What do pharmaceutical manufacturers expect from a new coater series that’s designed to offer them added value? An analysis of market requirements revealed that the focus should not be on a single aspect.

Fritz-Martin Scholz

Rather, the goal was to develop a state-of-the-art drum coater that meets a wide range of customer needs. The development team, comprising engineers and pharmacists, had to fulfil the following five requirements.

Closed material handling

The entire process sequence should be closed from filling to emptying and cleaning. The new Sepion series eliminates the need to open any doors during the ongoing process as it is filled and emptied using tubes with clamp connections that are integrated into the front door and can be equipped with split valves.

Uncoated tablet cores are extremely sensitive to breakage. In the Sepion coater, they slide into the mixing drum smoothly and gently. Sampling is just as easy and uncomplicated thanks to the sampling cylinder.

The mixing drum is emptied by means of reverse rotation via a closed system: specially shaped discharge baffles guide the tablets quickly and gently to the discharge opening in a continuous tablet stream, allowing a 500 L drum to be emptied in just a few minutes.

Containment

Safe containment is especially important to protect machine operators, products and the environment. When developing a new system, the containment concept should be considered right from the start — as was the case with the Sepion coater.

For example, the basic version can be upgraded to a containment coater with user-specific options. These essentially consist of split valves, safe-change filters and extended cleaning.

Flexible batch sizes

The Sepion coater is extremely flexible when it comes to batch sizes: the drum can be filled with product from a minimum of 10% up to a maximum of 100% of the working volume, thus offering wide application possibilities.

The design of the mixing baffles ensures gentle and thorough mixing at any fill level. The mixing quality was examined in extensive tests, during which tablets with three coatings were mixed.

At a fill volume of 100%, the specified relative standard deviation (RSD) of the mixture of less than 3% was successfully achieved after 8 minutes (Figure 1).

Figure 1: Mixing test at a fill volume of 100%: homogeneity was achieved after 8 minutes

Automatic spray arm

The automatic spray arm ensures that the correct distance between the spray nozzles and the tablet bed — as well as the correct inclination of the spray nozzles — can be set automatically for all filling heights (Figure 2).

Figure 2: The standard Sepion coater spray arm

The alignment is either recipe-controlled or done via an optional distance sensor. Depending on requirements, two variants of the spray arm are available: the standard and the pro spray arm.

With the standard spray arm, each spray nozzle is supplied with a separate liquid line. The pneumatic connection of the nozzles is partly achieved using hose connections.

The pro spray arm ensures pneumatic attachment to the spray nozzles mechanically and enables the connection of a common liquid supply and return, which greatly simplifies installation and cleaning (Figure 3).

The spray nozzles are positioned along the spray arm by a tool- and hose-free quick-connect system that avoids misalignments while greatly reducing set-up and cleaning times.

Figure 3: The pro Sepion coater spray arm

Process optimisation for best coating results

During development, a key aim was also to significantly reduce process times while maintaining high yields. Hence, the drum was lengthened in relation to its diameter.

On the one hand, this allows a higher number of spray nozzles to be used. On the other hand, the longer drum results in a flatter tablet bed, allowing individual tablets to pass through the spray zone more frequently.

The combination of both features facilitates higher spray rates and more uniform coating with shorter process times. Extensive tests with different tablets and filling quantities in comparison with an established coater have shown that the Sepion coater achieves significant improvements in process times while minimising the RSD of the coating.

The results presented here refer to a coating series with Opadry II (Figure 4). The objective was to achieve the required mass increase of 13% with a maximum spray rate and a high solid content of the spray solution (20%) in the shortest possible time.

Figure 4: Extensive testing provided clear results

The average weight of an uncoated tablet was 304 mg; the measured standard deviation within a sample of 500 tablets was 3.045 mg or 1% RSD (left side of diagram). After a process time of only 155 minutes, 345 kg tablets were coated. The average weight of a coated tablet was 344 mg with a standard deviation of 3.76 mg or 1.09% RSD.

Accordingly, the new Sepion coater is suitable for a wide range of applications — from cosmetic, non-functional coatings to enteric coatings, controlled release tablets and active ingredient coatings.

The Sepion coater also achieves very good values in terms of yield (98%). The effective use of the coating suspension saves process time, minimises product use and reduces cleaning efforts.

Optimised cleaning process

The new Sepion coater has also been optimised in terms of cleaning. The wash-in-place (WIP) rack is located in the technical area. The cleaning nozzles in the drum coater have been arranged in a way to ensure that all product-contact surfaces are safely reached.

In addition, the 360-degree high-pressure cleaning nozzle provides for even more intensive cleaning. All cleaning operations follow a validated, reproducible recipe and minimise manual intervention. Finally, the new touchscreen with integrated, intuitive operator guidance and optional process visualisation ensures safe operations.

The new, highly flexible Sepion coater is available in six sizes: from 175 and 250 through to 350 and 500 to 750 and 1000 L capacities. The thorough comparative tests have already convinced customers and the first Sepion coaters are currently being installed in greenfield projects in Europe and Asia.

In addition to its flexible batch size, the closed material handling and high spray rates with very low RSDs were the contributing factors that convinced these customers to invest in Syntegon technology.

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