Adsorption of zwitterionic drugs (beta-lactam antibiotics and amino acids) on samples of oxidized cellulose (OC) with various carboxyl contents and structure characteristics was investigated from aqueous and water/ alcohol solutions. The process is described according to the theory of localized stoichiometric adsorption and represented by Langmuir-like isotherms. The drug uptake increases with increase of alcohol content in the solution and with growth of alcohol molecular weight. The main contribution to the increase of drug uptake with addition of alcohol to the aqueous drug solution is provided by the desolvation of zwitterion ionic groups, which increases with growth of alcohol content. The structural characteristics of OC (degree of crystallinity and carboxyls distribution) and sorbate molecule size have considerable effect on the drug adsorption. It is shown that different drug uptake occurs on the CC samples with similar exchange capacity but various structure characteristics, which can be explained by various accessibility of carboxylic groups of OC, caused by decreased swelling of a sorbent in binary water/alcohol solutions.