Coating system for the manufacture of hormone preparations

One plant to meet all requirements

Handling highly potent substances requires complete processes to be isolated in order to protect staff and systems. “High containment” has become the magic word. As part of the production process, the coating machines likewise have to be integrated into the system. Haupt Pharma provides a good example of a successful solution. The company uses a LHC 190 coater.

The author: Horst Spittka Sales Life Science Technology, Gebr. Lödige Maschinenbau

With facilities in Germany, Italy, France and Japan and a representative office in the USA, the Haupt Pharma Group is one of the largest European companies for pharmaceutical order processing and manufacture. About 2000 employees there make products for leading pharmaceutical corporations. At its Münster plant with a workforce of over 230 the company is specialised, amongst other things, in the development and manufacture of products containing sex hormones in the form of film- and sugar-coated tablets. Handling sexual hormones as highly potent substances requires special equipment and machines to protect staff, the environment and the products themselves. Against this background Haupt Pharma recently set up a new production department for the manufacture of film- and sugar-coated tablets using state-of-the-art technology. The new plant consistently follows the closed, high containment principle to prevent contamination of the machine surroundings. The technical requirements were correspondingly complex: substances with Occupational Exposure Band (OEB) Classification 4 had to be processed safely. According to the requirements of BG Chemie, the German trade association of the chemical industry, the system must be isolated by special barriers. Furthermore, the coating system had to comply with the relevant CFR regulation (21 CFR Part 11) issued by the US Food and Drug Administration. This is a prerequisite of production for the US market. In addition, the solution had to satisfy the following criteria:
  • Suitability for film- and sugar-coating of very small tablets
  • Batch sizes for the two processes between 120 kg (starting weight) and 600 kg (final weight)
  • Compact, space-saving design, as the containment zone must be utilised as effectively as possible
  • Low energy and media consumption
  • Automatic production and cleaning
  • Coater with partially perforated drum
On the basis of these specifications and various tests a decision was taken to purchase a Type LHC 190 coater with a partially perforated drum from Gebrüder Lödige Maschinenbau. Besides the compact design, a horizontal coating drum with four exchangeable perforations is the main feature of this coater model. Only about 25 % of the cylindrical drum section is perforated; the coating drum itself is closed to the outside. The coater thus complies with the containment principle. The prepared – i. e. dehumidified, heated and filtered – air is introduced into the LHC 190 through an inlet in the coating drum and suctioned off by the exhaust fan through the perforations rotating beneath the product as well as four exhaust ducts. A rotary disc valve is used to control this continuous process. The maximum supply air volume is limited as a consequence of this design and the resulting pressure loss. However, the energy utilisation rate is very high, as there is little waste heat in the enclosed coating drum and the entire airflow is extracted through the product bed. Energy recovery by a heat exchanger between the intake and exhaust air further increases the efficiency of the system.
Special adjustment
This coater type has been in production at Lödige since 1980. The longstanding experience enabled the company to tailor the coater precisely to the needs of Haupt Pharma. In particular, a solution was called for which prevented the agglutination of small and hence light tablet cores in sugar-coating processes. These tend to stick to the drum wall, the mixing elements and each other. The reason for this is their low dead weight, which is often unable to resist the adhesive forces that occur due to the sugar suspension on the tablet surface. A series of measures prevent this undesirable effect: only one quarter of the coating drum wall is perforated while the remainder is smooth, making it ideally suited to sugar-coating processes. Furthermore, special ramp-shaped mixing elements prevent the cores from sticking to the front and rear. To improve the pre-distribution of sugar suspensions on the cores, the customary feed rakes were replaced by single-substance nozzles. These ensure far better pre-distribution of the suspension than feed rakes at pressures of 6 to 8 bar. The chosen solution has many benefits: since overconcentration of sugar-coating suspension on the wetted tablets is avoided, the mixing phase during coating with sugar is significantly reduced along with the batch times. Another effect of this optimised addition of liquid is that so-called “twins” are no longer formed. Parallel to the geometry of the mixing elements, the nozzle arm was also modified in order to achieve the required filling level variability. This modification allows the clearance between the nozzle and the tablets to be set to approximately 200 mm, even with extremely low filling levels of only 15 % of the drum volume. This is a particular advantage with film-coating processes. As the outflow angle of the tablets changes during the process, the nozzle angle of the spray arm can be adjusted exter-nally by means of a gear unit.
Containment measures implemented
Several modifications were necessary to the coater to enable perfect integration into the high-containment system. With the exception of the front door, the coating drum is already securely enclosed. Only the seals had to be specially designed for the high OEB 4 containment level. The coater is loaded with tablets for coating from barrels through a containment flap and a feeder. The tablet feeder, which projects into the coater, is drawn into a continuous plastic pouch after loading and cleaned sep-arately. After feeding, the dust is removed from the inside front part of the coater by a special compressed air blower and the particles resulting from the negative pressure during the entire process are suctioned off. This pneumatic dust removal step can be repeated as often as necessary depending on the dust accumulation in the front zone. It is carried out again prior to emptying the coater to avoid discharging product dust. Since the coated tablets no longer release critical dusts, they can be discharged without containment measures. The mixing elements have been modified for this purpose so that when the coating drum rotates in reverse, the tablets are conveyed to the front discharge and from there to a container placed in front of the coater. Both during the coating process and during feeding and discharge there is a vacuum in the coating drum to prevent the emission of product dust and thus contamination of the operating personnel or the machine surroundings. A by-pass for the exhaust air filter was dispensed with for containment reasons. Emissions of product dust are consequently impossible. However, the cleaning water must be more or less emptied from the system before drying to prevent overly moist exhaust air, which could clog the exhaust air filter. To rule out any impairment of the filter function, a largely moisture-resistant system was selected for the exhaust air. The dust is removed from the dust collector under safe-change conditions. The coater is cleaned by means of various cleaning nozzles using several different detergents. To avoid disrupting production, this process takes place automatically overnight. The plant is controlled by a combination of a PLC and a PC which fully conforms to the specifications of the US authority. Both film- or sugar-coating and cleaning processes can be performed automatically. The plant functions derived from the containment application, such as blow-off, were additionally implemented. The modified LHC 190 enables the requirements of OEB Classification 4 to be met without any restrictions. A second system has been ordered by Haupt Pharma.
Hall 5, Booth 222

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