Beta-lactam antibiotics, aminoglycosides, amphotericin B, cyclosporine, nonsteroidal anti-inflammatory drugs, antineoplastic, or antivirus drugs that are used extensively in clinical settings bear the risk of nephrotoxicity. This side effect is dose-dependent and has been attributed mainly to the accumulation of drugs in the renal proximal tubule. When assessing nephrotoxicity, both the dosage and the tubular secretion system, which allows transport of drug from blood to urine via the tubular cells, are important factors. This study was designed to investigate how renal transporters work in the renal secretion of specific drugs.