Solving Common Tableting Problems: Hardness, Weight Variation, and Capping

Pharmaceutical tableting continues to be a vital step in manufacturing oral solid dosage forms. Even with progress in formulation science and equipment, persistent problems like low tablet hardness, weight variation, and capping keep undermining quality, compliance, and patient safety. Such problems stem not only from the process itself but also from the more intricate interplay between formulation ingredients and material properties.

a) Low Tablet Hardness

Tablet hardness is a critical quality attribute (CQA) that shapes how durable the product is, how well it withstands packaging, and how it dissolves. It depends on the strength of interparticulate bonding, the compression force applied, and how the excipients deform.

Contributing Factors:

• Too little compaction force or dwell time [1]
• Weak cohesion, an unsuitable binder, or too little binder

Solutions Strategies:

• Fine-tune the compression parameters

Choose plastically deforming fillers such as microcrystalline cellulose (MCC). Add binder or raise its concentration to strengthen particle cohesion and, in turn, the tablet’s mechanical strength. Common binders like polyvinylpyrrolidone (PVP), or cellulose-based options such as hydroxypropylcellulose (HPC) and low-viscosity Hypromellose (PHARMACOAT®/TYLOPUR®), suit both granulation and direct compression. [2-3]

b) Weight Variation

Variation in tablet weight has a direct bearing on dosage accuracy and patient safety. Regulatory thresholds, for example those set out in USP <905> Uniformity of Dosage Units, demand that a tablet’s mass stay within a defined band around the target weight.

Root Causes:

• Uneven powder flow or segregation [4]
• Inconsistent die filling, particularly at high turret speeds, along with faulty feeders or misaligned tooling [5]

Control Measures:

Boost powder flow by introducing flow agents (for example, colloidal silicon dioxide), or by adopting granulation with binders to secure an adequate granule size.

c) Capping and Lamination

Capping describes the partial or full detachment of a tablet’s top or bottom portion. It arises from trapped air, too much elasticity, or insufficient bonding. Lamination, by contrast, is the horizontal splitting of a tablet into separate layers.

Primary Causes:

• Fast decompression that triggers elastic rebound [6]
• Insufficient pre-compression or missing dwell time
• Overly dry granules with low moisture or poor plasticity

Preventive Actions:

• Apply pre-compression to cut down on trapped air [7]

Keep granule moisture at an optimal level (usually around 1 to 2 % w/w for most excipients). Improve granule plasticity by optimizing the binder. PVP or fine HPC grades with an optimized surface area typically strengthen the cohesion of the tablet’s components. This binding action stops air pockets from forming and yields a more compact, uniform tablet. A further excipient that resolves capping and lamination is low-substituted L-HPC, particularly LH-11. Its long, interlocking fibers boost mechanical interparticulate bonding and lower ejection stresses during compression.

Conclusion

Ongoing tableting defects (low hardness, weight variation, and capping) reflect the intricate interplay among material properties, formulation design, and process parameters. Tackling them calls for a thorough grasp of powder characterization, compaction science, and equipment optimization. Putting an integrated Quality by Design (QbD) approach and control strategies in place gives a clearer view of the formulation design and production window, and it secures dependable product quality and compliance.

Continue reading the original Shin-Etsu article here

Source/ References:

Primary source: Setylose Blog, “Pharmaceutical Tableting.”

Further sources:
[1] ICH Q8 (R2): Pharmaceutical Development

[2] Aulton, M. E. & Taylor, K. (2017). Aulton’s Pharmaceutics: The Design and Manufacture of Medicines, 5th Ed.

[3] Rowe, R. C., Sheskey, P. J., & Quinn, M. E. (2009). Handbook of Pharmaceutical Excipients

[4] USP <905>: Uniformity of Dosage Units

[5] Hoag, S. W. (2011). Pharmaceutical Dosage Forms: Tablets, Vol. 1

[6] Lieberman, H. A., Lachman, L., & Schwartz, J. B. (1990). Pharmaceutical Dosage Forms: Tablets, Vol. 2

[7] EMEA: Guideline on the Manufacture of the Finished Dosage Form (CPMP/QWP/486/95)

Interested in more information or a sample from Shin-Etsu excipients?