ABSTRACT
Oral absorption of acidic or basic drugs can be predicted by the pH-partition theory, proposed by L. S. Schanker et al. This chapter describes orally active cephalosporins from the viewpoints of oral absorbability and biological evaluation, including both prodrug and nonprodrug. The ester-type prodrug approach was applied to cephalosporins, and several useful prodrugs have been developed for oral use. Remarkable progress of nonprodrug oral cephalosporins has also been achieved in Japan. The chapter discusses the effect of some physicochemical and biological properties on the oral absorbability of cephalosporin esters. The acylamido moiety at the C-7 position was chosen as a 2-(2-aminothiazol-4-y1)-(Z)-2-methoxyiminoacetamido function, which is widely employed in thirdgeneration cephalosporins used for injection. The effect of the C-3 substituents on the chemical and biological reactivity of β-lactam ring of cephalosporins has been investigated in detail by many groups. The C-3 substituent of cephalosporin enters was found to influence their chemical stability in a phosphate buffer solution.
