The purpose of this study was to investigate whether some non-steroidal anti-inflammatory drugs (NSAIDs) could cause inhibition of the growth of Lactobacillus casei Shirota (LcS) or whether this microorganism is able to use some of them as the sole carbon source, considering that the simultaneous consumption of NSAIDs and a dairy drink fermented with LcS could help to prevent the appearance or improve the healing of gastric ulcers. Acetylsalicylic acid (ASA), sodium acetylsalicylate (SAS), acetaminophen, sodium naproxen, and sodium ibuprofen were added as the sole carbon source to a basal medium and tested for biodegradation by LcS. The same NSAIDs were added in different concentrations to disks and plated on MRS Agar to test the possible inhibitory effect of these compounds on LcS. Also, the resistance of LcS to 12 different antibiotics was studied on MRS agar. None of the NSAIDs tested could be used by LcS as the sole carbon source at the assayed concentrations. In the case of the disk diffusion method, sodium naproxen showed inhibition zones for the 500-mu g disks and sodium ibuprofen was inhibitory for the 250- and 500-mu g disks. However, when the macrobroth dilution method was used, the growth of LcS was inhibited by ASA, SAS, acetaminophen, and sodium ibuprofen. This strain showed resistance to the antibiotics sulfamethoxazole with trimethoprim, pefloxacin, and gentamicin. This is the first study on the effect of NSAIDs on probiotic bacteria. The results of the biodegradation test indicate that the simultaneous consumption of NSAIDs and a dairy beverage with LcS is not likely to change the bioavailability of the drugs.