Interaction of some chemotherapeutic Agents with Human plasma proteins

Drug binding to various serum and tissue proteins can influence the therapeutic, pharmacodynamic and toxicologic actions of drugs . Protein binding may also exert a pro¬found effect on the drug distribution, The protein-drug co¬mplex may act as a transport system to carry the drug to the sites of action; this transport is extremely important for drugs that exhibit low solubility in the water portion of the plasma. 1’rotein binding slows the disappearance of free drug from the plasma into tissues by decreeing the. concentration gradient. It also provides a source of free drug to replace that removed by various distribution and elimination precedes. The binding equilibrium in often described by an association constant or constants together with the number of sites exhibiting each association cons¬tant. Such information is useful in establishing a proper dosage regimen. It is also of importance when two or more -drugs, that strongly bind to protein and compete for the same binding sites, are administered concurrently. Higher free drug concentrations are thereby produced and may pre¬cipitate a toxic response. ;such increase in pharmacological activity of the displaced drug often necessitates an adjust¬ment in dosage, The binding to human albumin of a new drug should be examined, especially the drug is an acidic molecule, because competitive binding with serum protein among acidic drugs has been shown it to be particularly signi¬ficant. Sulfamethoxazole, medium-acting sulfonamide, is used in respiratory infections and urinary tract infection.