High pressure membrane processes such as nanofiltration (NF) and reverse osmosis (RO) play a pivotal role in the treatment of water. Although RO/NF membranes effectively remove most of organic compounds, especially pharmaceutically active compounds, their major drawback is membrane fouling and they require chemical cleaning process. The aim of chemical cleaning is to return membrane performance and achieve a long membrane life. This paper examined efficiency of chemical cleaning of RO/NF membranes after adsorption of albendazole. For this purpose three RO (UTC–70HA, BW30, XLE) and three NF (NF, NF90, NF270) membranes were investigated. Commercially available formulated chemical cleaning reagents – namely Nalco PermaClean99 and solution of sodium hydroxid (NaOH), ethylenediaminetetraacetic acid (EDTA) were used for the membrane cleaning experiments. FTIR analysis and retention factor proved interactions i.e, adsorption of albendazole on membranes during the separation process. Before cleaning process, impact of chemical clenanig reagents on the membrane was examined. FTIR analyses of the virgin and cleaned membranes showed no discernible impact of chemical cleaning reagents on bonding structure of membranes investigated here. It is shown that caustic cleaning led to increase in the permeate flux of the NF270, NF i BW30 membranes. FTIR analyses after chemical cleaning showed that selected cleaning reagents didn't remove albendazole from the membrane surface i.e., membranes weren't cleaned successfully.