Tablets are the most used oral dose type in the pharmaceutical sector. They have numerous benefits, the most important of which are their capacity to precisely manage dosage and the great stability of active substances.
Tablets can be created quickly and in huge quantities, allowing for greater design freedom in terms of size, form, and color. They can be effervescent, dissolving, or dispersible; dissolving tablets, lozenges; enteric-coated and retarding tablets; and uncoated and coated tablets.
Image Credit: Soho A Studio/Shutterstock.com
Tablet coatings
Tablets are commonly coated. This entails adding a thin film of one or more polymers and other functional excipients (colorants or humectants) on the tablet, which can serve various purposes.
Tablets are coated to control the release of the active ingredient, such as in enteric-coated or extended-release dose forms, to protect the active ingredient from light or moisture or to hide a bitter taste in the tablet formulation.
Tablets are also coated to improve swallowability or for color (for unique identification or marketing). Coating with active substances is becoming increasingly significant.
This covers combination goods and the use of two incompatible active substances in the same dosage form. Furthermore, multiple release profiles of the same active component can be blended. In this example, the slow-release component is located in the core, whereas the fast-release initial dose is found in the tablet coating.
Image Credit: L.B. Bohle Maschinen und Verfahren GmbH
Formulation procedures can include up to four film kinds, leading to extended processing times. Coating consistency is required for the successful development and production of such formulations.
The Relative Standard Deviation (RSD) measures coating uniformity and is highly analytically significant.
The lower the RSD, the more uniform the tablet's coating. However, correct determination of the RSD requires significant analytical effort because the same individual tablets must be tested before and after coating, or coating components must be quantified using content determination methods.
Image Credit: L.B. Bohle Maschinen und Verfahren GmbH
Color difference (ΔE) for colored coatings differs from RSD uniformity measurement. High ΔE values indicate a considerable hue change.
The dimensionless quantity ΔE is sometimes equated with coating uniformity in percentage RSD, although this is a severe error that can radically affect a method's validity.
Mixing, spraying and drying
Mixing, spraying, and drying are essential in tablet coating. To achieve the best coating uniformity, they must be done simultaneously with the proper parameters.
Mixing
Smooth and careful movement of the tablet cores beneath the spray cones is required. To prevent damage, tablet cores should not be subjected to severe mechanical stress. For almost 20 years, L.B. Bohle (Ennigerloh, Germany) has successfully used an extended coating drum (length/diameter (L/D) > 1) with welded-in mixing spirals.
The mixing spirals ensure that the tablet bed is continuously and gently mixed. Homogeneous mixing occurs within minutes and is maintained throughout the operation. The flat tablet bed lowers the melt pressure in the tablet bed.
Because of the continual direction of the mixing spirals, the tablets are not significantly accelerated, and tablet breakage and twinning do not occur.
Drum geometry, spray arm design, and reduced coating time
The drum design of the L.B. Bohle BFC tablet coater allows for a broad spray area in the moving tablet bed.
This allows for more spray nozzles than in shorter drums, resulting in a bigger overall spray area and a higher spray rate. In addition to the coating suspension, the nozzle type, number of nozzles, and distance between nozzles are all critical considerations.
L.B. Bohle provides various methods for changing the nozzle bed distance, spray angle, and atomization pressure. Typically, the suspension mass of film-coated tablets ranges from 5 to 15% of the core mass.
The film thickness is particularly critical, as it must be uniform for thin color (protective) coatings and active component coatings. Uneven film application within a batch, for example, causes color variances that lower product quality or compliance.
Larger drum systems can reduce process durations by up to 40% compared to traditional tablet coaters with low L/D ratios. This is due to increased spray rates.
Drying
It is vital to ensure efficient energy and mass transfer. This requires that the energy be applied directly to the tablet bed. The air travels directly and softly into the tablet bed, quickly drying the sprayed suspension.
There is no heating of the coater's perimeter or housing. Optimal airflow produces a smooth spray pattern, reducing spray drying. The supply air stream does not touch spray nozzles and stays cool during the spraying procedure. This reduces spray drying effects, resulting in >97% or greater coating uniformity.
World premiere at Interpack 2023 - Coater optimized in terms of process, technology, and machine execution
L.B. Bohle tablet coaters have been in the market for almost two decades and are considered technologically advanced. Through extensive customer interaction, ongoing cross-departmental research, and process optimization, L.B. Bohle has improved the BFC series.
This has resulted in advancements in technology/machine equipment, cleaning, usability and safety, hygienic design, and sustainability. The goal is to optimize the daily manufacturing process by making it more flexible, faster, resource-efficient, uniform, and feasible.
Image Credit: L.B. Bohle Maschinen und Verfahren GmbH
In terms of machine equipment, the emphasis is on a modern machine control system. The iFix program allows you to monitor and control the processes. As a Human Machine Interface (HMI), iFix provides the elements required for operation.
Crucial data, such as long-term data storage of measured values, warnings and messages, data interfaces to external systems, and a recipe management system, are recorded.
The necessity of covering small quantities is steadily increasing. Significant flexibility in production equipment is needed in addition to existing laboratory coaters. The BFC tablet coater provides maximum versatility, allowing 10 to 100% batch sizes.
This translates to batch sizes ranging from 65 to 650 l with a BFC 400. L.B. Bohle revised the BFC's nozzle block. The nozzle angle and distance are motorized and automatically adjusted. Furthermore, the nozzle block has become smaller and more rounded. This makes cleaning easier, and the bigger sight glass enables more accurate process monitoring.
Easier to operate and safer
The coating process is already heavily mechanized. Nonetheless, operators are present throughout the process to provide in-process controls, visual evaluations, and material sampling. L.B. Bohle has specifically implemented the operator instructions in the new tablet coater.
The side door can now be opened and closed with pneumatic cylinders, reducing the necessary force. The air supply shoes are separated, significantly reducing weight and improving handling.
Safety concerns have also been considered. Inflatable seals are now standard. The fully automatic sample and loading of tablets with the door closed improves operator safety.
The control panel is now more hygienic, and a status light in the machine's front allows for process monitoring.
Fast discharge and effective cleaning
After the coating operation, the coater is rapidly, gently, and thoroughly discharged by reversing the rotational direction and changing the inclination. This is followed by completely automated cleaning.
An extra cleaning lance at the bottom of the unit is now included as standard. Further enhancements shorten cleaning time and ensure the cleaning medium drains swiftly and without residue.
Focus on sustainability
The pharmaceutical sector generates significant greenhouse emissions and consumes a lot of energy. L.B. Bohle addressed energy consumption in the new coater design.
For the first time, L.B. Bohle incorporates optional heat recovery into the ventilation system, significantly reducing energy usage. A new energy monitoring system for the coater's energy supply provides manufacturers with a thorough insight into their process and consumption.
About L.B. Bohle Maschinen und Verfahren GmbH
L.B. Bohle with the headquarter in Germany, is one of the largest system suppliers for the pharmaceutical processing industry and related sectors. Internationally active, they focus on machinery and equipment as well as process technology and components.
In addition, L.B. Bohle offer sustainable solutions for demanding production processes in batch and continuous manufacturing for the oral solid dosage production. For instance, L.B. Bohle provides single or interlinked machines for the processes Weighing, Dry and Wet Granulation, Grinding and Sieving, Container Blending, Tablet Coating and Tablet Handling.
Sponsored Content Policy: News-Medical.net publishes articles and related content that may be derived from sources where we have existing commercial relationships, provided such content adds value to the core editorial ethos of News-Medical.Net which is to educate and inform site visitors interested in medical research, science, medical devices and treatments.