Oxytetracycline (terramycin) is a linear, tetracyclic broad spectrum antibiotic originally isolated from Streptomyces rimosus in 1949. Like all tetracyclines, oxytetracycline shows broad spectrum antibacterial and antiprotozoan activity and acts by binding to the 30S and 50S ribosomal sub-units, blocking protein synthesis. Oxytetracycline, although less coloured than other tetracyclines, is still a pigment and is thus sensitive to environmental and storage conditions. Commercial oxytetracycline may contain significant levels of degradation products.