# Tablet Scoring: Current Practice, Fundamentals, and Knowledge Gaps
## 6 Tablet Scoring: Challenges and Opportunities
Size reduction is a step that is commonly used after the granulation step to eliminate the oversize granules [209; 210]. For formulations that are designed for tablet splitting, this step plays a crucial role. (2) Blending and Mixing (Blend Uniformity)  
The uniformity of a powder blend is dependent on the excipients used in the formulation and the mixing approach. Mixing is an energy consuming process which produces a random distribution of particles [211]. Poor blend uniformity can potentially produce tablets with poor content uniformity [212]. The efficiency of the mixer dictates the uniformity of the blend. Mixer efficiency is dependent on the following factors: type of mixer used, operating speed, mixing time, blend volume. Particle size, shape, density, and cohesively can also influence mixing [213]. Mixing involves the following steps:  
* Convective movement of the particles from various location within the mixer [214]. * Shear movement, which is the cascading effect of the particles within the mixer [215]. * Diffusive movement of the particles as a result of increasing mobility [216]. Blend uniformity is an important factor to consider when developing a formulation suitable for tablet splitting. Blend uniformity ensures content uniformity within the tablets [212]. For tablet splitting it is important to have homogenous distribution of the drug substance in the powder blend, to ensure content uniformity in the split tablets. (3) Tablet Compression and Tooling Design  
Powder segregation should be controlled during tablet compression [160] Discharging the powder blend from the tote to the hopper tablet press introduces powder transportation effects. During the  
Figure 6: Factors to consider for tablet formulations in order to facilitate proper splitting. transport of powders, there is a constant migration of particles. Due to differences in trajectories of particles with different masses and/or sizes, these particles will be separated during transportation [217]. The shape of the particles also plays an important role during this type of segregation process [218]. Special precautions must be taken during handling of these powders by reducing the transportation velocity or the falling height segregation is minimized [217]. In order to overcome this effect, a valve is designed and placed with a certain angle at the junction of the mixer to the hopper of the tablet press [219]. The speed of the turret can introduce percolation effect where gravity causes smaller particles to move into the voids between larger particles, due to relatively larger differences in particle sizes [220]. The tablet press turret and feeder speed should be optimized in order to control powder vibration. Smaller sized particles will gradually move under the bigger sized particles, leading to a separation between differently sized particles [221]. In addition, tablet compression forces should be controlled in order to produce tablets with physical properties that are amenable for scoring [222]. Tablet splitting effectiveness is dependent on the following tablet properties. * Hardness (good breakability will not crumble during splitting)
* Thickness (bulkier tablets can be difficult to split)
* Good friability (tablets are not brittle and do not loose mass during splitting)  
Finally, tablet tooling design is also important [223], as tooling geometry and the depth of the debossed score line influence the ability to effectively score tablets. Ineffective, tablet splitting may result in the administration of an inaccurate dose, which can be of significant risk if the split medication is a narrow therapeutic index medication. Several studies have reported weight differences among partitioned tablets [224]. Numerous studies have assessed drug content uniformity only as a variation in half tablet weights [224; 225]. However, very few studies have explored the in-vitro drug content of half tablets. The current United States Pharmacopeia (USP) guidelines for drug content of split tablets are loosely defined.