NoyesWhitneytörvény

The Noyes Whitney law, also known as the Noyes Whitney equation, is an empirical relationship used in pharmaceutical science to describe the dissolution rate of a solid drug in a liquid medium. Developed by William Noyes and William Whitney in 1903, the equation models how quickly a drug dissolves, which is a critical factor in its bioavailability and therapeutic effectiveness.

The Noyes Whitney equation states that the rate of dissolution is directly proportional to the surface area of the dissolving solid and the difference in concentration between the saturated solution at the surface of the solid and the bulk solution. Mathematically, it is often expressed as dM/dt = k * A * (Cs - Cb), where dM/dt represents the rate of mass dissolution, k is the dissolution rate constant, A is the surface area of the dissolving solid, Cs is the saturation solubility of the drug, and Cb is the concentration of the drug in the bulk solution.

This equation highlights several key factors influencing dissolution. A larger surface area, achieved through smaller particle sizes or techniques like micronization, leads to faster dissolution. A higher concentration difference (meaning the bulk solution is far from saturation) also promotes a quicker dissolution rate. The dissolution rate constant (k) is influenced by various factors, including the properties of the solid, the solvent, and the hydrodynamics of the system, such as stirring speed.

The Noyes Whitney equation is fundamental in understanding and predicting drug dissolution. It is widely applied in the formulation of solid dosage forms, such as tablets and capsules, to optimize the release profile of active pharmaceutical ingredients. By controlling particle size, excipients, and manufacturing processes, formulators can manipulate dissolution rates to achieve desired therapeutic outcomes. However, it is important to note that this is an empirical model and may not perfectly predict dissolution under all conditions, especially for complex systems or poorly soluble drugs.