Drug concentration protein binding

M) for plasma proteins than for their specific binding sites (receptors). In the range of therapeutically relevant concentrations, protein binding of most drugs increases linearly with concentration (exceptions salicylate and certain sulfonamides). 

Drug Therapeutic serum concentration (pg/ml) Bioavailabitity (for oral drugs)(%) Plasma protein binding(%) Kd(Ukg) ti/2(h)... 

The prindpal permeability barrier is represented by the luminal surface of the brush border. Most dmgs are absorbed by passive diffusion in their un-ionised state. The pH of the small intestine determines the degree of ionisation and hence controls the effidency of absorption this is the basis of the pH-partition theory of drug absorption. Protein binding at the serosal side of the epithdium hdps maintain a concentration gradient by binding the absorbed dmg, which is then removed by blocxl flow from the absorption site. 

Sulfaphenazole (684) and sulfazamet (685) are both examples of relatively short acting sulfonamides (B-80MI40406) and their antibacterial activity has been tested against Escherichia coli, the former being more effective than the latter. Sulfaphenazole also displaces sulfonyl ureas from protein binding sites on human serum albumin and consequently increases the concentration of the free (active) drug and produces a more intense reaction that may result in hypoglycemia. 

Some AEDs, especially phenytoin and valproate, are highly bound to plasma proteins. When interpreting a reported concentration for these drugs, it is important to remember that the value represents the total (i.e., bound and unbound) concentration in the blood. Because of differences in the metabolism of these drugs, the clinical effects of altered protein binding are different for different drugs. 

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