| Indication | Used to treat bacterial infections such as Rocky Mountain spotted fever, typhus fever, tick fevers, Q fever, rickettsialpox and Brill-Zinsser disease. May be used to treat infections caused by Chlamydiae spp., B. burgdorferi (Lyme disease), and upper respiratory infections caused by typical (S. pneumoniae, H. influenzae, and M. catarrhalis) and atypical organisms (C. pneumoniae, M. pneumoniae, L. pneumophila). May also be used to treat acne. Tetracycline may be an alternative drug for people who are allergic to penicillin. |
| Pharmacodynamics | Tetracycline is a short-acting antibiotic that inhibits bacterial growth by inhibiting translation. It binds to the 30S ribosomal subunit and prevents the amino-acyl tRNA from binding to the A site of the ribosome. It also binds to some extent to the 50S ribosomal subunit. This binding is reversible in nature. Additionally tetracycline may alter the cytoplasmic membrane of bacteria causing leakage of intracellular contents, such as nucleotides, from the cell. |
| Mechanism of action | Tetracycline passively diffuses through porin channels in the bacterial membrane and reversibly binds to the 30S ribosomal subunit, preventing binding of tRNA to the mRNA-ribosome complex, and thus interfering with protein synthesis. |
| Absorption | Bioavailability is less than 40% when administered via intramuscular injection, 100% intravenously, and 60-80% orally (fasting adults). Food and/or milk reduce GI absorption of oral preparations of tetracycline by 50% or more. |
| Volume of distribution | Not Available |
| Protein binding | 20 - 67% protein bound |
| Metabolism | Not metabolized |
| Route of elimination | They are concentrated by the liver in the bile and excreted in the urine and feces at high concentrations in a biologically active form. |
| Half life | 6-12 hours |
| Clearance | Not Available |
| Toxicity | LD50=808mg/kg (orally in mice) |