Drug distribution factors affecting

Drug distribution is affected by many factors/ including plasma or tissue protein binding/ body weight/ body composition/ and body fluid spaces (8). Of these/ total body weight/ muscle masS/ and fat composition are the major determinants of drug distribution/ and women may differ from men in both of these factors. 

Juliano, R. L. (1988) Factors affecting the clearance kinetics and tissue distribution of liposomes, microspheres and emulsions dv. Drug Deliv. Rev., 2 31-54. 

Factors analogous to those affecting gut absorption also can affect drug distribution and excretion. Any transporters or metabolizing enzymes can be taxed to capacity—which clearly would make the kinetic process nonlinear (see Linear versus Nonlinear Pharmacokinetics ). In order to have linear pharmacokinetics, all components (distribution, metabolism, filtration, active secretion, and active reabsorption) must be reasonably approximated by first-order kinetics for the valid design of controlled release delivery systems. 

Furthermore, pharmacokinetic administration, distribution, metabolism and excretion (ADME) factors affect drug bioavailability, efficacy and safety, and, thus, are a vital consideration in the selection process of oral drug candidates in development pipelines. Since solubility, permeability, and the fraction of dose absorbed are fundamental BCS parameters that affect ADME, these BCS parameters should prove useful in drug discovery and development. In particular, the classification can used to make the development process more efficient.For example, in the case of a drug placed in BCS Class II where dissolution is the rate-limiting step to absorption, formulation principles such as polymorph selection, salt selection, complex formation, and particle size reduction (i.e., nanoparticles) could be applied earlier in development to improve bioavailability. 

Since each of these and other factors may singly or in combination affect absorption, you can see why it is so difficult to specify a drug effect for a person under specific conditions at a given time. This discussion also reaffirms why intravenous injection is the most efficient way to get a drug to its sites of action. Intravenous injection bypasses many factors that may retard absorption because it puts the drug in direct contact with the blood—the vehicle of drug distribution. 

Understanding the physiology of lactation and pharmacokinetic factors affecting drug distribution, metabolism, and elimination can assist the clinician with more appropriate... 

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