Background: Glutathione S-transferase (GST) and acetylcholinesterase (AChE) are important enzymes in the metabolism. GSTs are primarily available in phase II metabolism. AChE is vital for neurodegenerative disorders. Subjects and methods: The in vitro and in vivo effects of cefoperazone sodium (CFP), cefuroxime (CXM), and cefazolin (CZO) were investigated on GST and AChE activity in the present study. GST was purified using Glutathione-Agarose affinity chromatography. Results: K-i constants of CFP, CXM, and CZO were 0.1392 +/- 0.02, 1.5179 +/- 0.33, and 1.006 +/- 0.11 mM for GST and 0.3010 +/- 0.07, 0.3561 +/- 0.09, and 0.3844 +/- 0.04 mM, for AChE, respectively. The most effective inhibitor was CFP for both enzymes in in vitro. CZO (50 mg/kg), CXM (25 mg/kg), and CFP (100 mg/kg) inhibit in vivo GST and AChE activities. CXM had the most effective in vivo inhibition on AChE and GST. Conclusions: CZO, CXM, and CFP are effective AChE and GST inhibitors in both in vitro and in vivo.