Micromeritics is the science and technology of small particles. The knowledge and control of the size of particles is of importance in
pharmacyPharmacy is the health profession that links the health sciences with the chemical sciences and it is charged with ensuring the safe and effective use of pharmaceutical drugs...
and
materials scienceMaterials science is an interdisciplinary field applying the properties of matter to various areas of science and engineering. This scientific field investigates the relationship between the structure of materials at atomic or molecular scales and their macroscopic properties. It incorporates...
. The size, and hence the
surface areaSurface area is the measure of how much exposed area a solid object has, expressed in square units. Mathematical description of the surface area is considerably more involved than the definition of arc length of a curve. For polyhedra the surface area is the sum of the areas of its faces...
of a particle, can be related to the physical, chemical and pharmacologic properties of drugs. Clinically, the particle size of a
drugA drug, broadly speaking, is any substance that, when absorbed into the body of a living organism, alters normal bodily function. There is no single, precise definition, as there are different meanings in drug control law, government regulations, medicine, and colloquial usage.In pharmacology, a...
can affect its release from dosage forms that are administered orally, parenterally, rectally and topically. The successful
formulationFormulation may refer to:* Clinical formulation* Formulations * Formulation science* Pharmaceutical formulation:** Galenic formulation* Pesticide formulation...
of suspensions, emulsions and tablets; both physical
stabilityChemical stability when used in the technical sense in chemistry, means thermodynamic stability of a chemical system.Thermodynamic stability occurs when a system is in its lowest energy state, or chemical equilibrium with its environment. This may be a dynamic equilibrium, where individual atoms...
and pharmacologic response also depends on the particle size achieved in the product.
Origin
The term was created by J. M. DallaValle in his book
Micromeritics: the technology of fine particles. It was derived from the Greek word for small and part. The size range which he covered in the book was from 10
−1 to 10
5 micrometers. Anything smaller than this but bigger than a
moleculeA molecule is an electrically neutral group of at least two atoms held together by covalent chemical bonds. Molecules are distinguished from ions by their electrical charge...
were referred to at the time as colloids but are now often referred to as nanoparticles. Applications included
soil physicsSoil physics is the study of soil physical properties and processes. It is applied to management and prediction under natural and managed ecosystems. Soil physics deals with the dynamics of physical soil components and their phases as solids, liquids, and gases. It draws on the principles of...
,
mineral physicsA mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...
,
chemical engineeringChemical engineering is the branch of engineering that deals with physical science , and life sciences with mathematics and economics, to the process of converting raw materials or chemicals into more useful or valuable forms...
,
geologyGeology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...
, and
hydrologyHydrology is the study of the movement, distribution, and quality of water on Earth and other planets, including the hydrologic cycle, water resources and environmental watershed sustainability...
. Characteristics discussed included particle size and shape,
packingIn geometry, a sphere packing is an arrangement of non-overlapping spheres within a containing space. The spheres considered are usually all of identical size, and the space is usually three-dimensional Euclidean space...
, electrical,
opticalRayleigh scattering, named after the British physicist Lord Rayleigh, is the elastic scattering of light or other electromagnetic radiation by particles much smaller than the wavelength of the light. The particles may be individual atoms or molecules. It can occur when light travels through...
, chemical and
surface scienceSurface science is the study of physical and chemical phenomena that occur at the interface of two phases, including solid–liquid interfaces, solid–gas interfaces, solid–vacuum interfaces, and liquid-gas interfaces. It includes the fields of surface chemistry and surface physics. Some related...
.
Release and dissolution
Particle size and surface area influence the release of a drug from a dosage form that is administered
orallyThe mouth is the first portion of the alimentary canal that receives food andsaliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth....
, rectally parenterally and topically. Higher surface area brings about intimate contact of the drug with the
dissolutionDissolution is the process by which a solid, liquid or gas forms a solution in a solvent. In solids this can be explained as the breakdown of the crystal lattice into individual ions, atoms or molecules and their transport into the solvent. For liquids and gases, the molecules must be compatible...
fluids
in vivoIn vivo is experimentation using a whole, living organism as opposed to a partial or dead organism, or an in vitro controlled environment. Animal testing and clinical trials are two forms of in vivo research...
and increases the
drugA drug, broadly speaking, is any substance that, when absorbed into the body of a living organism, alters normal bodily function. There is no single, precise definition, as there are different meanings in drug control law, government regulations, medicine, and colloquial usage.In pharmacology, a...
solubilitySolubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a solid, liquid, or gaseous solvent to form a homogeneous solution of the solute in the solvent. The solubility of a substance fundamentally depends on the used solvent as well as on...
and dissolution.
Absorption and drug action
Particle size and
surface areaSurface area is the measure of how much exposed area a solid object has, expressed in square units. Mathematical description of the surface area is considerably more involved than the definition of arc length of a curve. For polyhedra the surface area is the sum of the areas of its faces...
influence the
drugA drug, broadly speaking, is any substance that, when absorbed into the body of a living organism, alters normal bodily function. There is no single, precise definition, as there are different meanings in drug control law, government regulations, medicine, and colloquial usage.In pharmacology, a...
absorptionIn pharmacology , absorption is the movement of a drug into the bloodstream.Absorption involves several phases...
and subsequently the therapeutic action. Higher the dissolution, faster the absorption and hence quicker and greater the
drugA drug, broadly speaking, is any substance that, when absorbed into the body of a living organism, alters normal bodily function. There is no single, precise definition, as there are different meanings in drug control law, government regulations, medicine, and colloquial usage.In pharmacology, a...
action.
Physical stability
Micromeritic properties of a particle, i.e. the particle size in a
formulationFormulation may refer to:* Clinical formulation* Formulations * Formulation science* Pharmaceutical formulation:** Galenic formulation* Pesticide formulation...
, influence the physical stability of the suspensions and emulsions. Smaller the size of the particle, better the physical stability of the
dosage form-Introduction:Dosage forms are a mixture of active drug components and nondrug components. Depending on the method of administration they come in several types. These are liquid dosage form, solid dosage form and semisolid dosage forms. A Liquid dosage form is the liquid form of a dose of a...
owing to the
Brownian motionBrownian motion or pedesis is the presumably random drifting of particles suspended in a fluid or the mathematical model used to describe such random movements, which is often called a particle theory.The mathematical model of Brownian motion has several real-world applications...
of the particles in the
dispersionDispersion may refer to:In physics:*The dependence of wave velocity on frequency or wavelength:**Dispersion , for light waves**Dispersion **Acoustic dispersion, for sound waves...
.
Dose uniformity
Good flow properties of granules and
powdersA powder is a dry,thick bulk solid composed of a large number of very fine particles that may flow freely when shaken or tilted. Powders are a special sub-class of granular materials, although the terms powder and granular are sometimes used to distinguish separate classes of material...
are important in the
manufacturingManufacturing is the use of machines, tools and labor to produce goods for use or sale. The term may refer to a range of human activity, from handicraft to high tech, but is most commonly applied to industrial production, in which raw materials are transformed into finished goods on a large scale...
of tablets and capsules. The distribution of particles should be uniform in terms of number and
weightIn science and engineering, the weight of an object is the force on the object due to gravity. Its magnitude , often denoted by an italic letter W, is the product of the mass m of the object and the magnitude of the local gravitational acceleration g; thus:...
.