Advanced Tablet-Coating Technologies Aid Manufacturing Efficiency

New coating technologies achieve high uniformity and reduce waste through mixing system advances and pan and airflow configuration.
Jun 01, 2012

As the pharmaceutical market continues to grow, tablet manufacturers face countless operational decisions that impact their ability to compete. Processing efficiency is one of the most important issues, affecting time-to-market, budgets, and product margins.

Advanced tablet-coating technologies increase manufacturing efficiency and help manufacturers produce more tablets in less time by improving coating uniformity, reducing coating solution waste, and minimizing cleaning and maintenance.

Improved uniformity

Figure 1: Patented, high-efficiency coating drum (L.B. Bohle).
The biggest limitation of traditional tablet coaters is the amount of time and solution required to achieve uniformity. Typically, for a cosmetic coating (i.e., instant-release coating) using a conventional coater, tablet weight must increase 4–5% to achieve a uniform coat. The newest drum coaters, however, achieve the same coverage with only a 1.5–2% weight gain, primarily due to an advanced mixing system and pan configuration.

Figure 2: (a) Unmixed tablets are (b) fully mixed after 10 min. in a high-efficiency coater (Bohle Tablet Coater, L.B. Bohle).
This improved uniformity and mixing effect results in better distribution of the coating solution on the tablet surface. Thus, with a lower weight gain, manufacturers are able to achieve the color specification required.

Mixing system

Table 1: Percentages of each tablet color in the front, middle, and back of the coating pan demonstrate complete mixing after 10 min.
The mixing system of a high-efficiency coater uses patented spiral baffles to move tablets constantly, as shown in Figure 1. One of the baffles moves tablets to the back of the pan while the other brings them forward. In 10 min or less, manufacturers can attain tablet homogeneity in each batch as was demonstrated in a mixing experiment with white, red, and green tablets (see Figure 2). In this experiment, an approximate 500 mL sample was taken from the front, middle, and back of the mixer after 2, 5, and 10 min, and the percentage of white, red, and green tablets in each location was calculated. As shown in Table I, the tablets in the middle were almost perfectly mixed after 2 min, and all zones were completely mixed after 10 min.