Pharmaceuticals and Particle Size Measurement

The Efficacy and Safety of Medicines

In the field of medicines and pharmaceuticals, particle size distribution directly influences "effectiveness" and "safety" and, in some situations, it might become a major life-related issue.

With medicines and pharmaceuticals that are difficult to dissolve in a body fluid, their area of contact with fluid can be increased and their dissolution speed in fluid can be accelerated by pulverization. Yet, too great a dissolution speed will make the concentration higher than necessary and sometimes causes side effects.

Thus, to manufacture medicines and pharmaceuticals that are more effective and that have fewer side effects, the particle size distribution must be controlled.

Particle size distribution control is important also for ensuring the homogeneity of medicines and pharmaceuticals. Generally, pills, tablets and capsules are made by mixing two or more medicines and pharmaceuticals. If there is variance in the mixture ratio, this will cause the "effectiveness" to differ in each individual pill, tablet or capsule, and the homogeneity, consistency and safety as a medicine or pharmaceutical will be impaired.

To ensure this homogeneity, and enhance product consistency and quality, the fluidity of the raw materials in manufacturing processes and consistency, etc. in the blending process must be enhanced. Particle size distribution greatly affects homogeneity, consistency and quality in these processes, too.

Besides this, positive attempts are being made to fully utilize the nature of particles.

Joint research is being conducted by the First Department of Surgery, Miyazaki University School of Medicine and the Miyazaki Prefecture Industrial Technology Center into the application of emulsions formed by a new technology "membrane emulsification technique" to the treatment of liver cancer. Currently, research has progressed to the clinical testing stage.

They are attempting to make antineoplastic agents act stably at high concentrations in a limited manner on only cancer cells by encasing particles of aqueous solution containing antineoplastic agents with oil particles having a high affinity with cancer cells and administering these particles to the hepatic artery. They say that revolutionary effectiveness comparable with surgery can be expected and that an outstanding feature of this application is that it causes hardly any side effects.

Other research institutes also are conducting basic research using emulsions to administer immunosuppressants to patients after organ transplants.

In all of these cases, the particle size distribution of emulsions is a major factor for determining their effectiveness and side affects.

Specific Surface Area and Pore Distribution of Pharmaceuticals

Clays such as aluminum silicate (acid clay) are used for stomach medicines. These porous materials have a large surface area, which functions to absorb gastro-intestinal toxic bacteria and abnormal matter, absorb surplus moisture to stop diarrhea, and protect the gastro-intestinal membrane.

Dissolution testing (dissolution time and rate) is one kind of method for evaluating medicines and pharmaceuticals. The fact that the specific surface area is large means that the area of contact with solids and surrounding liquids is large, and so it is said that dissolution testing and the size of the specific surface area are in a direct correlation to each other.

In the case of pills and tablets, their strength and porosity (fraction of the volume of voids over the total volume of a sample) is closely related to their physical properties.

Lactose is water-soluble, and is used as a vehicle in medicines and pharmaceuticals since it has small reactivity to living organisms. Moreover, it goes without saying that the same solubility as that of active ingredients is required for vehicles, too. The chief factor affecting this solubility is specific surface area.