In this paper, the in vivo effects of some antibiotics including cefazolin, cefuroxime, and cefoperazon, on the activity of the carbonic anhydrase enzyme (CA) in heart, brain, eye, liver, and kidney tissues of rats were evaluated. For this purpose, 16 different groups, which each containing six rats (n = 6), were formed (control group, cefazolin groups, cefuroxime groups, and cefoperazon groups). The rats were necropsied 60 min after the intraperitoneal injection of the chemicals into the rats. The CA activities were measured for each tissue using esterase activity methods. The activity values for each tissue obtained were statistically calculated. The CA activities in the liver tissue were assessed, and the activities of the cefoperazon groups were decreased compared to the sham groups from the third hour (p<0.05). In the cefuroxime and cefoperazon groups, the CA activities in the eye tissue were decreased during the first 3 h and then increased (p<0.05).