Pharmaceutical Analysis: What effect does particle size have on solubility?

Pharmaceutical Analysis: What effect does particle size have on solubility?


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  • Source: Microbioz India

  • Date: 10 Feb,2023

In the pharmaceutical industry, particle size is a key factor since it affects surface area and porosity, which in turn affects a drug’s bioavailability, effectiveness, and shelf life. Particle size is therefore examined in the creation of new active medicinal components as well as in quality control (APIs). In fact, while assessing novel medications, particle size distribution (PSD) is one of the most crucial criteria to look at.

What Does It Mean to Have a Distribution of Particle Size in Pharmaceuticals?

The term “particle size distribution(PSD) refers to a measurement that is used in the pharmaceutical business to define the range of sizes of particles that are present in a certain medicine. When it comes to the creation of brand-new pharmaceutical goods, the PSD is one of the most crucial evaluation metrics. In most cases, sieve analysis, laser diffraction, dynamic image analysis, or dynamic light scattering are the techniques that are utilised to perform PSD measurements.

Because of their unique forms, the particles in a pharmaceutical product may have varying dimensions at various points. When measuring particles, the diameter is the characteristic that is utilised when the particles are nearly perfect spheres. It’s possible that other kinds of particles, such those with an ovoid or irregular shape, have length and breadth measurements. The most accurate results can be achieved by obtaining horizontal and vertical measurements, although doing so is a more complicated process than just determining a diameter. As a result, the majority of measurements make the assumption that each particle is a spherical, but they only report an estimated diameter.

The size of the particles in pharmaceuticals and their solubility:

One of the important parameters to consider in order to achieve the desired concentration of drug in systemic circulation in order to produce the desired (anticipated) pharmacological response is solubility, which refers to the phenomenon of dissolving a solute in a solvent to produce a homogenous system. When developing formulations for new chemical entities or developing generic versions of existing drugs, one of the most significant challenges that can be faced is low water solubility. More than forty percent of the new chemical entities (NCEs) generated by the pharmaceutical industry are so insoluble in water that they are essentially unusable.

How does the size of the particles affect the solubility?

The size of the particles does, in fact, have an effect on the apparent solubility. When dissolved in water, particles that have been reduced to an extremely small size (micronized or nanonized), potentially reaching a higher maximum concentration (or solubility) than a typical crystalline product is capable of achieving. This is because there are less crystal lattice interactions per amount of chemical if the particle size is lowered, which may result in supersaturation in comparison to the thermodynamic solubility of the substance. This supersaturated concentration is metastable, which means that it can cause precipitation if it persists long enough.

It is common knowledge that the dissolution of solutes takes place on the surface. This indicates that the activity is only taking place on the surface of each individual particle. The total surface area of the solute particles expands as a molecule of the solute is broken down into smaller particles and then further broken down into even smaller particles. This indicates that the solute will dissolve at a faster rate. Therefore, fragmenting a solute into smaller bits will increase its surface area, which will, in turn, result in an increased rate of solvation or solubility.

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