4-Epioxytetracycline is the 4-epimer of oxytetracycline, a semisynthetic derivative of tetracycline antibiotics. It is primarily recognized as a common impurity or degradation product in oxytetracycline production and formulations. While it retains some antibacterial activity against gram-positive and gram-negative bacteria, its potency is significantly reduced compared to oxytetracycline. In veterinary medicine, it may be present in trace amounts in antibiotic preparations for livestock, but its main applications are as a reference standard in pharmaceutical quality control, residue analysis in food and animal tissues, and research on tetracycline stability, epimerization, and antibiotic resistance mechanisms.