Serum protein binding alterations of selected cephalosporin antibiotics by fatty acids and their derivatives.

Saturated fatty acids containing 10--14 carbon atoms were more potent inhibitors of serum protein binding than those containing shorter or longer carbon chains. Introduction of unsaturation into chains containing 16 or 18 carbons increased their inhibitory potency. Triglycerides and fatty acid esters, chlorides, thiols, and amides had no inhibitory activity. When inhibition was observed, it was concentration dependent and occurred when the molar ratio of fatty acid to protein equaled or exceeded three. The change in percent serum protein binding in the presence of an effective inhibitor was the greatest with cephalosporins that were most highly bound in the absence of an inhibitor.