distribution coefficient การใช้

• This quantitative measure is known as the distribution ratio or distribution coefficient.
• The distribution coefficient ( D ) considers the partitioning of all ionic species of the compound.
• Hence the hydrophobicity of a compound ( as measured by its distribution coefficient ) is a major determinant of how drug-like it is.
• A number of methods of measuring distribution coefficients have been developed, including the shake-flask, reverse phase HPLC, and pH-metric techniques.
• In the context of pharmacokinetics ( what the body does to a drug ), the distribution coefficient has a strong influence on ADME properties of the drug.
• Many other industries take into account distribution coefficients for example in the formulation of make-up, topical ointments, dyes, hair colors and many other consumer products.
• Where Kd ( l g-1 ) represents the distribution coefficient, and n is the slope of the straight line giving an indication of the H + / M z + stoichiometry of the exchange reaction.
• Furthermore, the lipid solubility of the nonionized species is slight as shown by its low logP value ( log ( 10 ) of the distribution coefficient of the nonionized form between octanol and water ) of-1.43.
• According to JiY
  ?H醠a's text book, the distribution coefficient K d is the ratio of the soil's radioactivity ( Bq g  " 1 ) to that of the soil water ( Bq ml  " 1 ).
• A drug's distribution coefficient strongly affects how easily the drug can reach its intended target in the body, how strong an effect it will have once it reaches its target, and how long it will remain in the body in an active form.
• For cases where a drug reaches its target locations through passive mechanisms ( i . e ., diffusion through membranes ), the ideal distribution coefficient for the drug is typically intermediate in value ( neither too lipophilic, nor too hydrophilic ); in cases where molecules reach their targets otherwise, no such generalization applies.
• Hence, a single experiment can be used to measure the logs of the partition coefficient ( log " P " ) giving the distribution of molecules that are primarily neutral in charge, as well as the distribution coefficient ( log " D " ) of all forms of the molecule over a pH range, e . g ., between 2 and 12.
• The "'distribution coefficient "', "'log " D " "', is the ratio of the sum of the concentrations of all forms of the compound ( ionized plus un-ionized ) in each of the two phases, one essentially always aqueous; as such, it depends on the pH of the aqueous phase, and log " D " = log " P " for non-ionizable compounds at any pH . For measurements of distribution coefficients, the pH of the aqueous phase is buffered to a specific value such that the pH is not significantly perturbed by the introduction of the compound.
• The "'distribution coefficient "', "'log " D " "', is the ratio of the sum of the concentrations of all forms of the compound ( ionized plus un-ionized ) in each of the two phases, one essentially always aqueous; as such, it depends on the pH of the aqueous phase, and log " D " = log " P " for non-ionizable compounds at any pH . For measurements of distribution coefficients, the pH of the aqueous phase is buffered to a specific value such that the pH is not significantly perturbed by the introduction of the compound.