1. Introduction
Pharmaceutical microcrystalline cellulose (MCC) is widely used as a filler and binder in oral solid dosage forms. For high-drug-load tablet formulations with API content above 60%, standard MCC grades such as PH-101 and PH-102 may present die-filling limitations and higher tablet-weight variability because of their lower bulk density (typically 0.28-0.32 g/cm³).
DESU® MCC PH-301 and DESU® MCC PH-302 are high-density grades developed from PH-101 and PH-102-type particle-size profiles. Optimized spray-drying increases bulk density while retaining plastic deformation behavior. DESU® MCC PH-301 has a finer particle size (D50 approximately 50 μm) for smaller tablet formats and high-density filling, while DESU® MCC PH-302 has a particle size around 100 μm and is suited to high-speed direct compression.
This study evaluates DESU® MCC PH-301 and DESU® MCC PH-302 as MCC excipients for high-drug-load direct compression using a metformin model formulation (60% API). Performance was compared with equivalent European, Japanese, and American benchmark products, focusing on powder properties, lubricant sensitivity, loading capacity, compactibility, and tablet-weight consistency.
2. Experimental Methods
2.1 Physicochemical Indicators and Powder Characterization
Loss on drying (dried at 105°C to constant weight), pH value, and degree of polymerization were determined according to Chinese Pharmacopeia standards. Graduated cylinder method was used to measure loose bulk density (LBD) and tapped bulk density (TBD), and Carr's index was calculated (CI = (TBD-LBD)/TBD × 100%).
2.2 Lubricant Sensitivity Testing
Pharmaceutical microcrystalline cellulose samples from different sources were blended with 1% magnesium stearate (20 rpm, 10 min) and directly compressed. Five compression-force levels (4, 6, 8, 12, and 15 kN) were evaluated for tablet hardness, friability, and disintegration time. The Lubricant Sensitivity Index (LSI) was defined as hardness at low pressure (6 kN) divided by hardness at medium pressure (12 kN); a lower LSI indicates greater lubricant sensitivity.
2.3 Loading Capacity and Compactibility Evaluation
Simulated formulation: metformin 60% + MCC 35% + sodium starch glycolate 2% + magnesium stearate 0.5-0.8%. Tablet weight was 500 mg, main compression pressure was 8-15 kN, and target hardness was >100 N. Maximum loading capacity, tablet hardness, and tablet-weight RSD were measured.
3. Results and Discussion
3.1 Physicochemical Indicators and Powder Characteristics
Table 1 summarizes the physicochemical properties of four high-density MCC products. MCC PH-302 has a bulk density of 0.43 g/cm³, 43.3% higher than standard MCC PH-102 (0.30 g/cm³), while MCC PH-301 reaches 0.41 g/cm³, a 36.7% increase. The degree of polymerization of MCC PH-301 (265) and MCC PH-302 (272) is comparable to the benchmark products (263-278), and pH values of 6.2-6.6 fall within the stated 5.0-7.5 range.
Table 1 Comparison of Physicochemical Indicators of High-Density MCC from Different Sources
| Source | Bulk Density (g/cm³) | Tapped Density (g/cm³) | Degree of Polymerization | pH Value | Carr's Index (%) |
| MCC PH-301 | 0.41 | 0.52 | 265 | 6.2-6.5 | 21.1 |
| MCC PH-302 | 0.43 | 0.55 | 272 | 6.3-6.6 | 21.8 |
| European Brand | 0.42 | 0.54 | 270 | 6.1-6.4 | 22.2 |
| Japanese Brand | 0.44 | 0.56 | 278 | 6.4-6.7 | 21.4 |
| American Brand | 0.41 | 0.53 | 263 | 6.2-6.5 | 22.6 |
Carr's index was 21.1% for MCC PH-301 and 21.8% for MCC PH-302, compared with 28.5% for standard MCC PH-102. The lower values indicate improved powder flow, an important attribute for high-speed tableting and consistent die filling.
Figure 1 Comparison of Bulk Density of High-Density MCC from Different Sources
3.2 Lubricant Sensitivity Evaluation
Table 2 compares the direct-compression performance of four PH-302 products after addition of 1% magnesium stearate. In the 4-6 kN low-pressure range, MCC PH-302 produced tablet hardness of 48-62 N, compared with 45-58 N for the European benchmark, 52-68 N for the Japanese benchmark, and 50-65 N for the American benchmark. Friability was <0.3% for all four products.
Table 2 Comparison of Direct Compression Performance of PH-302 with Lubricant from Different Sources
| Source | Low Pressure Hardness (N) | Medium Pressure Hardness (N) | High Pressure Hardness (N) | Friability (%) | LSI Index |
| MCC PH-302 | 48-62 | 95 | 118 | <0.3 | 0.62 |
| European Brand | 45-58 | 92 | 115 | <0.3 | 0.60 |
| Japanese Brand | 52-68 | 98 | 122 | <0.3 | 0.65 |
| American Brand | 50-65 | 96 | 120 | <0.3 | 0.63 |
Note: Low pressure range 4-6 kN, medium pressure 12 kN, high pressure 15 kN
The LSI results in Figure 2 show differences in lubricant sensitivity among PH-302 products. The Japanese benchmark had the highest LSI (0.65), followed by the American benchmark (0.63), MCC PH-302 (0.62), and the European benchmark (0.60). The LSI of MCC PH-302 falls within the 0.60-0.65 range observed in the comparison and indicates that its densified structure retains plastic deformation behavior during compression.
Figure 2 Lubricant Sensitivity Index (LSI) Calculation Results of MCC PH-302 with 1% Magnesium Stearate from Different Sources
3.3 Process Robustness of DESU® MCC PH-301 and DESU® MCC PH-302
Under the same test conditions, MCC PH-301 showed low-pressure hardness of 55-72 N versus 48-62 N for MCC PH-302, with LSI values of 0.61 and 0.62, respectively. The similar LSI values indicate comparable lubricant sensitivity and process robustness between the two high-density grades.
Table 3 Comparison of Process Robustness between PH-301 and PH-302
| Grade | Low Pressure Hardness (N) | Medium Pressure Hardness (N) | LSI Index | Process Robustness Evaluation |
| MCC PH-301 | 55-72 | 98 | 0.61 | Robust |
| MCC PH-302 | 48-62 | 95 | 0.62 | Robust |
The performance difference is mainly associated with particle-size distribution. MCC PH-301 has a finer particle size (D50 approximately 50 μm) and larger specific surface area, while MCC PH-302 has a larger particle size (D50 approximately 100 μm), higher bulk density, and characteristics suited to high-speed tableting.
3.4 High-Drug-Load Capacity and Compactibility
At a main compression pressure of 15 kN, the two MCC grades were compared in 500 mg simulated tablets containing 60% metformin:
Table 4 Comparison of Loading Capacity and Compactibility
| Evaluation Indicator | MCC PH-102 | MCC PH-302 | Improvement |
| Maximum Loading Capacity (%) | 65.5 | 88.2 | +22.7% |
| Tablet Hardness (N) | 125 | 118 | -5.6% |
| Tablet Weight RSD (%) | 2.8 | 0.7 | -75.0% |
At 15 kN, MCC PH-302 produced tablet hardness of 118 N versus 125 N for standard MCC PH-102, while remaining above the >100 N target. More importantly, maximum API loading increased from 65.5% to 88.2%, and tablet-weight RSD decreased from 2.8% to 0.7%. The higher bulk density of MCC PH-302 increases fill mass and reduces air entrainment during high-speed feeding, helping improve tablet-weight consistency.
Figure 3 Comparison of Loading Capacity of Different MCC Products
4. Conclusion
This study evaluated DESU® MCC PH-301 and DESU® MCC PH-302 as high-density MCC excipients for direct compression of high-drug-load tablets, focusing on powder density, hardness-pressure behavior, lubricant sensitivity, compactibility, and loading capacity:
(1) High-density advantage: MCC PH-302 reaches a bulk density of 0.43 g/cm³, 43.3% above standard MCC PH-102, while MCC PH-301 reaches 0.41 g/cm³. These higher-density grades address die-filling constraints in high-drug-load formulations.
(2) Process robustness: MCC PH-302 has an LSI of 0.62, within the range observed for the imported benchmark products. The study recommends magnesium stearate at 0.5-0.8% and main compression pressure above 7 kN.
(3) Higher loading capacity: At tablet hardness >100 N, MCC PH-302 reached a maximum API loading capacity of 88.2%, 22.7 percentage points above standard MCC PH-102, while tablet-weight RSD decreased from 2.8% to 0.7%.
(4) Application fit: MCC PH-302 is suited to conventional high-drug-load, high-speed direct compression (machine speed >80,000 tablets/hour; pressure 8-12 kN), while MCC PH-301 is suited to smaller tablet formats requiring a finer particle size (D50 approximately 50 μm).
Overall, DESU® MCC PH-301 and DESU® MCC PH-302 provide high-density pharmaceutical microcrystalline cellulose options for high-drug-load tablet formulations. In the metformin model used in this study, the high-density grades supported improved filling performance and direct compression while maintaining the target tablet hardness.