Issue link: http://www.e-digitaleditions.com/i/477622
26 March 2015 Tablets & Capsules Most tablet presses include systems that can control and/or monitor weight and thickness and can adjust the settings to ensure tablets meet their specifications. The systems can also identify, isolate, and reject off-spec tablets. But sometimes the system either misidentifies the tablet or isolates the wrong one. For this and other rea- sons, some manufacturers continue to rely on sorters to ensure they've made good tablets. They claim that dimensional sorting is equivalent to the automatic sorting method used with hard gelatin capsules, which removes empty and partially filled capsules based on weight. While I have no knowledge of the FDA ever objecting to the use of those systems to sort capsules, the differences between tablets and capsules raise some questions. First, generally speaking, and assuming a nominal amount of API in the blend, there is much less risk of overfilled capsules than there is of overweight tablets. Second, there are fewer hard shell capsule products that contain APIs with a narrow therapeutic index [7]. Third, the FDA is likely to question manufacturers that rely on sorting to ensure quality, as the following excerpt from a 2010 warning letter indicates [8]: For example, it appears that as part of your batch release criteria you rely on a practice of sorting and rejecting tablets with quality defects as a quality con- trol measure. It is our expectation that firms take a sys- tematic approach to correcting and complying with CGMP to ensure the identity, strength, quality, and purity of their drug products. In other words, sorting is seen as an attempt at "inspect- ing in" quality rather than adding a layer of protection. Roll sorter operation It's important to recognize the limitations of dimen- sional sorters. No mechanical sorter can detect and remove foreign tablets based on color differences or for- eign tablets that are the same size and shape as good product. Furthermore, in cases where a tablet's thickness and its minor axis are the same or nearly so, some roll sorters will fail to distinguish between the two. Some machines are also mechanically complex and may require frequent maintenance and/or calibration. Critical opera- tional features of roll sorters include: Slide gate position. The slide gate controls the flow of tablets from the feed hopper to the feeding track, and the tablets should reach the rollers in a controlled man- ner and without disruption. Vibration amplitude. Vibratory feeding provides more precise control than a slide gate. Excessive vibration, however, will cause the tablets to jump as they reach the rollers, possibly allowing unacceptable tablets to pass as acceptable. Plastic tablet guide position. Some machines use guides on the feeding track to divert tablets across the rollers (photo). Proper setup requires some trial and error. Roller speed. How fast the rollers turn determines how fast the tablets move over the rollers. Most machines allow you to adjust roller speed, but some don't. Whatever the setting, either a timing belt or a series of gears ensures that all rollers turn at the same speed. Roller gap. The size of the gap between the rollers changes along their length: narrow at first, on-spec at the midpoint, and wide at the end (Figure 1). Standardizing the setup GMP requires that you calibrate and verify the accept/reject methods of your process [9]. Some dimen- sional sorters have a computer-assisted setup feature that Roll sorter with plastic guides to divert tablets Figure 1 Progressive gap between rollers for separating thin (underweight), standard (on-spec), and thick (overweight) tablets g = good g - x g + x