Model Formula Release For Free

First order model: The release of drug can be represented by the equation: DC/dt=-K1C K1 is the first order rate constant, expressed in time-1 or per hour After rearranging and integrating the equation, Log C=log C0-K1t/2.303 C0 is the initial concentration of the drug, C is the percent of drug remaining at time t.

Ft = Q = A ?D(2C ? Cs) Cs t (7) where Q is the amount of drug released in time t per unit area A, C is the drug initial concentration, Cs is the drug solubility in the matrix media and D is the diffusivity of the drug molecules (diffusion coeffi- cient) in the matrix substance.

Zero Order Model, First Order Model, Higuchi Model, Peppas Model and Hixon Crowell Model are used in 85% of drug release studies in total.

Higuchi Model It assumes that the initial drug concentration in the film is much higher than the solubility of the drug in the ointment base. Henceforth, drug release will comprise drug dissolution and diffusion.

These models are based on different mathematical functions, which describe the dissolution profile. The basic kinetic models used are - Zero order model, - First order model, - Higuchi model, - Hixson-Crowell model. is the zero order release constant expressed in units of concentration/time.

?It is a process by which a drug leaves a drug product & is subjected to ADME & eventually becoming available for pharmacological action.? It involves the study of drug release rate, dissolution /diffusion/erosion studies and the study of factors affecting release rate of the drug.

The basic mechanisms that control the release of the drug molecules through the polymeric layer are osmosis, dif- fusion, chemical degradation, swelling and dissolution, with diffusion play- ing a dominant role in many CR systems. Diffusion-controlled systems are mainly of the reservoir and the matrix designs.