Ceftiofur sodium is a third generation cephalosporin which is active against number of gram positive and gram negative bacteria. It has bactericidal properties, acting by inhibition of the bacteria cell wall synthesis. Cephalosporins are reported to cause the gastrointestinal complications for which the simultaneous use of the acid suppressing drugs like H2-receptor antagonists are prescribed. It is quite possible that co-administration of one drug may affect the performance of the other drug and vice versa. The aim of the present work is to investigate the effect of the co-administration of ceftiofur sodium and cimetidine which is well established H2-receptor antagonist. The studies have been carried out by pH simulation as full gut at normal and elevated temperature