Determination of Tablet Hardness

Tablet hardness, also known as tablet crushing strength, is a critical quality attribute that determines the
tablet’s ability to withstand mechanical stress during handling, packaging, and transportation. The hardness of a
tablet directly influences its disintegration and dissolution properties, as well as patient compliance. Various
methods are used to determine tablet hardness during pharmaceutical manufacturing. Let’s explore how tablet
hardness is determined:

Method: Tablet Hardness Tester

The most common method used to measure tablet hardness is through the use of a tablet hardness tester, also known
as a hardness tester or a tablet compression tester. This equipment applies a controlled force to the tablet,
measuring the peak force required to break or fracture the tablet. The tablet hardness tester typically consists
of the following components:

• Anvil: A flat surface on which the tablet rests during the test.
• Punch: A rod or probe that exerts a downward force on the tablet.
• Force Sensor: The sensor that measures the force applied to the tablet.
• Display Unit: The display unit shows the hardness value in units like kg/cm² or N/mm².

Procedure:

The tablet hardness test is conducted as follows:

1. A tablet is placed on the anvil of the hardness tester.
2. The punch is then brought down to apply force to the tablet until it fractures.
3. The force required to break the tablet is recorded by the force sensor and displayed on the unit.

Factors Affecting Tablet Hardness:

Several factors can influence the hardness of tablets, and it is essential to consider them during formulation and
manufacturing processes. Some of these factors include:

• Formulation: The selection of excipients and their proportions can affect tablet hardness.
  Using appropriate binders and diluents can help achieve the desired hardness.
• Compression Force: The force applied during tablet compression impacts the hardness. Higher
  compression force generally results in harder tablets.
• Particle Size and Distribution: The size and distribution of the drug and excipient particles
  influence tablet hardness.
• Granule Properties: In granulation processes, the properties of granules formed can affect
  tablet hardness. Properly sized and uniform granules contribute to consistent hardness.
• Lubrication: The use of lubricants can affect tablet hardness, as excessive lubrication may
  lead to softer tablets.
• Moisture Content: Tablets with high moisture content can have reduced hardness due to reduced
  inter-particulate bonding.

Importance of Tablet Hardness:

Tablet hardness is a critical quality attribute in pharmaceutical manufacturing for several reasons:

• Hardness ensures the tablet’s mechanical strength, preventing breakage during handling and transportation.
• Appropriate hardness influences the tablet’s disintegration and dissolution rates, affecting drug release
  profiles and bioavailability.
• Hardness is a key factor in patient compliance, as excessively hard or soft tablets may be difficult to
  swallow.
• During coating processes, hard tablets are less prone to chipping or damage.
• Tablet hardness serves as a quality control parameter to ensure consistent product performance.

Conclusion:

Tablet hardness is a crucial parameter in pharmaceutical manufacturing, impacting tablet integrity, drug release
rates, and patient acceptability. The use of a tablet hardness tester allows manufacturers to measure and control
tablet hardness accurately, ensuring the production of high-quality tablets that meet the required specifications.