Tetracycline

Tetracycline is a broad-spectrum antibiotic produced by the Streptomyces genus of actinobacteria. It has a bacteriostatic effect on a wide range of gram-positive and gram-negative pathogens. It is used to treat a number of infections. These include acne, cholera, brucellosis, plague, malaria, and syphilis. It is taken by mouth. Tetracycline requires a prescription and is on the World Health Organization's list of essential medicines.

Pharmacodynamics

Tetracycline passively diffuses through pore channels in the bacterial membrane and reversibly binds to the 30S ribosomal subunit, preventing tRNA binding to the mRNA-ribosome complex and thus interfering with protein synthesis. As a result, bacteria are unable to proliferate further and can be more easily eliminated by the immune system.

Pharmacokinetics

Bioavailability is less than 40% with intramuscular administration, 100% intravenously, and 60-80% orally (fasting adults). Food and/or milk reduce GI absorption of oral tetracycline preparations by 50% or more. Plasma protein binding is approximately 20-70%. Excretion is by the kidney and the half-life is 6-12 hours.

Drug Interactions

Tetracycline may be inactivated by iron, aluminum or calcium. Therefore, dairy products, iron supplements, and antacids should be avoided while taking it.

Side effects:

• Yellowing of the teeth.
• photosensitivity of the skin, so exposure to the sun or intense light is not recommended
• drug-induced lupus and hepatitis
• fatty liver
• Tinnitus

Toxicological data

LD50 (mouse,oral): 678 mg-kg-1