Tetracyclines

The tetracyclines are broad-spectrum, bacteriostatic antibiotics that are active against many pathogens including gram positive and gram negative bacteria, spirochetes, chlamydia, leptospira, mycoplasma and rickettsia. They are widely used in medical practice, but currently have restricted usefulness. Tetracyclines act by binding to bacterial ribosomes inhibiting protein synthesis. Bacterial resistance is common and is usually caused by plasmids that decrease the bacterial cell wall permeability. At least eight different tetracyclines are currently available in the United States: tetracycline, doxycycline, minocycline, tigecycline, sarecycline, omadacycline, eravacycline and demeclocycline. Several others tetracyclines have been used in the past in the United States or Europe, but have been withdrawn (chlortetracycline, aureomycin, triacetyloleandomycin, rolitetracycline, oxytetracycline). While all tetracyclines are capable of causing a distinctive form of acute fatty liver disease when given intravenously in high doses, liver injury from oral forms tetracyclines vary greatly in frequency and clinical features. Minocycline is the most commonly implicated tetracycline in causing liver injury and generally ranks within the 10 most common causes of drug induced liver injury in developed nations. Minocycline hepatotoxicity generally presents with a long latency, hepatocellular enzyme elevations, prominent autoimmune features, apparent response to corticosteroid therapy and relatively bengn course. Doxycycline, in contrast, usually presents with a short latency (within 60 days), a cholestatic course, mild immunoallergic or autoimmune features and sometimes prolonged, but ultimately benign course. The other tetracyclines have had limited clinical use and are generally suspected but unproven potential causes of liver injury. References updated: 10 April 2019