Yes, stearic acid can affect the disintegration time of coated tablets, including those containing Tolperisone HCl.

Here’s how and why:

1. Hydrophobic Nature of Stearic Acid

Stearic acid is a hydrophobic lubricant, meaning it repels water.

It can form a water-repellent film around granules or tablets, especially if used in excess or poorly blended.

This film can impede water penetration, delaying disintegration and potentially slowing dissolution.

2. Concentration Matters

Typical use level is 0.5%–3% w/w.

Higher concentrations (>1%) increase the risk of slower disintegration, especially in low-porosity tablets.

In coated tablets, the effect may be compounded due to the added barrier from the coating layer.

3. Mixing Time & Method

Over-mixing with stearic acid can worsen the hydrophobic barrier.

Ideally, it should be added last and mixed gently to avoid overcoating particles.

4. Coating Influence

If the film coating is not water-soluble or has limited permeability, the delay from stearic acid becomes more significant.

The combined effect can lead to non-compliance with pharmacopeial disintegration specs.

Recommendations

Evaluate disintegration time vs. stearic acid level using a factorial design.

Consider using alternative lubricants like:

Magnesium stearate (with care—also hydrophobic),

Sodium stearyl fumarate (less hydrophobic),

Colloidal silica + talc (for better wetting/disintegration balance).

If stearic acid is necessary, optimize granule porosity and coating permeability.

Tri Phan, Stearic acid is a hydrophobic lubricant, commonly used in tablet formulations to reduce friction during tablet compression. While effective for improving manufacturability, hydrophobic lubricants are known to form a water-repellent film on the surface of powder particles, which can hinder wetting and penetration of water, thereby delaying tablet disintegration and drug dissolution.

In your case, the core tablet disintegrates within 5 minutes, which suggests that the stearic acid level in the core is within acceptable limits and not significantly impeding disintegration.

However, after applying a film coating, the disintegration time doubles to 10 minutes. This increase is not unusual, and multiple factors could be responsible such as (Seal Coating or Sub-Coating, Coating Thicknes, and Core-Coating Interaction). Therefore, while stearic acid alone in the core may not have caused a dramatic delay in disintegration, the combined impact of the lubricant and the coating especially if both are hydrophobic can explain the observed increase from 5 to 10 minutes. This does not necessarily mean that disintegration time always doubles after coating, but rather that the specific formulation and coating system used in this case contribute synergistically to that delay.

To mitigate this, consider:

• Reducing the concentration of stearic acid or switching to a less hydrophobic lubricant like magnesium stearate in lower amounts or sodium stearyl fumarate.
• Optimizing the coating formulation, possibly using more hydrophilic film-formers or including superdisintegrants in the coating (e.g., in fast-dissolving film coatings).
• Evaluating coating thickness (weight gain) and ensuring it's within the optimal range to avoid over-coating.

In conclusion, yes, stearic acid can indirectly affect the disintegration of a coated tablet, particularly when its hydrophobicity works in tandem with a non-permeable or slowly dissolving coating.