5 Prerequisites for Tablet Coating

What pharmaceutical manufacturers should expect from a state-of-the-art coater

September 10, 2021

4 Min Read
Fritz-Martin Scholz, product manager at Hüttlin, a Syntegon Technology Co.Image courtesy of Syntegon Technology

Fritz-Martin Scholz, product manager, Hüttlin, a Syntegon Technology Co.

Fritz-Martin Scholz, product manager at Hüttlin, a Syntegon Technology Co. in Schopfheim, Germany, talks about what pharmaceutical manufacturers should expect from a state-of-the-art coater.

Tablet coating is a demanding and important process step in tablet production. Only a precise and tailor-made coating meets both the coloring and taste masking, as well as the more demanding requirements such as enteric coatings, retarded release coatings, or an active ingredient application. So what should be taken into account when designing a new coater? Market requirements show that the focus should not be on a single aspect. Rather, the goal is to develop a state-of-the-art drum coater that meets all customer needs, which can be divided into five distinct aspects:

* Closed material handling
* Containment options
* Flexible batch sizes
* An automatic spray arm
* Significant process improvements


1. Closed Material Handling

As far as closed material handling is concerned, the entire process sequence should be closed from filling to emptying and cleaning. Any new coater should eliminate the need to open doors during the ongoing process, when filled and emptied via tubes with clamp connections integrated into the front door, which can be equipped with split valves. In the case of uncoated tablets--which are extremely sensitive to breakage--they should slide into the mixing drum smoothly and gently. Sampling should be just as easy and uncomplicated as is discharging and ideally allow a continuous tablet stream, so that a 500-l drum can be emptied in just a few minutes.

2. Containment Options

The second point is containment. This is especially important to protect everyone and everything involved in the process (i.e. machine operators, products, and the environment). When developing a new system, the containment concept should be considered right from the start, and basic coater versions should be upgradable to containment coaters with user-specific options. These essentially consist of split valves, safe-change filters, and extended cleaning.

3. Flexible Batch Sizes

Number three is flexibility--especially regarding batch sizes. Imagine a drum that can be filled with product from a minimum of 10% up to a maximum of 100% of the working volume. This will offer wide application possibilities. A special design of the mixing baffles can further ensure gentle and thorough mixing at any fill level. The mixing quality was examined in extensive tests, where tablets with three coatings were mixed. At 100% filling, the specified relative standard deviation (RSD) of the mixture of less than 3% was undercut during the tests after eight minutes.


4. Automatic Spray Arm

The fourth aspect is the spray arm. It all depends on the degree of automation and connectivity: Every spray arm must have a certain level of automation to ensure the correct distance of the spray nozzles to the tablet bed and to provide the correct inclination of the spray nozzles so they can be set automatically for all filling heights. In the best case, the spray nozzles are positioned along the spray arm by a tool-free quick-connect system without hose connection. This avoids misalignments, while greatly reducing setup and cleaning times.


5. Process Improvements

Finally, process optimizations play a central role in all new equipment. For a new coater, this primarily means reducing process times while maintaining high yields. This can be achieved, for example, by lengthening the drum in relation to its diameter. On one hand, this allows for a higher number of spray nozzles; on the other hand, it results in a flatter tablet bed, allowing the individual tablet 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.

Fritz-Martin Scholz is product manager at Hüttlin, a Syntegon Technology Co. (Schopfheim, Germany). Syntegon (formerly Bosch Packaging Technology) is a leading global process and packaging technology provider for pharmaceutical and food manufacturers. For more information, visit www.syntegon.com

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