- The patient must not be pregnant or nursing. Tetracycline (Demeclocycline, Doxycycline, Minocycline, Tetracycline, and Tigecycline) are classified as FDA pregnancy category D. Maternal ingestion of Tetracyclines during pregnancy may cause tooth discoloration, enamel defects, and other congenital anomalies. Tetracyclines are excreted in human breast milk; however, the extent of absorption of Tetracyclines by the breastfed infant is not known.