Facts About Tetracycline Antibiotics

Tetracyclines were discovered in the late 1940s and were extremely popular when they were first introduced.

Tetracyclines got their name because they share a chemical structure that has four rings. They were originally derived from soil bacteria Streptomyces aureofaciens.

Tetracycline antibiotics are broad-spectrum bacteriostatic agents, that inhibit bacterial protein synthesis and may be effective against a wide variety of microorganisms.

These medications are used in the treatment of infections of the respiratory tract, sinuses, middle ear, urinary tract, skin, intestines. They are also used to treat Gonorrhoea. Their most common current use is in the treatment of moderately severe acne and rosacea.

The most commonly prescribed tetracycline antibiotics are: tetracycline, doxycycline, minocycline, oxytetracycline.

How do they work?

Tetracyclines act at the ribosomal level where they interfere with the protein synthesis of susceptible bacteria. They also have several non-antibiotic properties, which are not well understood:

• Anti-inflammatory effects
• Inhibition of metalloproteinases (enzymes that inhibit collagen and gelatin production)
• Reduction of new blood vessel formation (angiogenesis)
• Reduction of programmed cell death (apoptosis)

Resistance to Tetracyclines

One of the major drawbacks of tetracyclines is the development of resistance. Resistance to these drugs occurs in two main ways: ribosomal protection and efflux of drug outside of cell. Cross-resistance to all of the drugs in the tetracycline class is due to these two mechanisms.

Tetracyclines side effects

Common side effects associated with tetracyclines include cramps or burning of the stomach, diarrhea, sore mouth or tongue. Tetracyclines can cause skin photosensitivity, which increases the risk of sunburn under exposure to UV light. This may be of particular importance for those intending to take doxycyline long-term doxycyline on holidays as a malaria prophylaxis.

Rarely, tetracyclines may cause allergic reactions. Very rarely severe headache and vision problems may be signs of dangerous secondary intracranial hypertension.

These antibiotics should not be used in children under the age of 8, and specifically during periods of tooth development. Tetracyclines are classed as pregnancy category D. Use during pregnancy may cause alterations in bone development.

Effects on contraceptives

There is little evidence that tetracyclines reduce the efficacy of the birth control pill unless they cause gastrointestinal upset. However, to be absolutely safe, extra precautions should be taken, particularly in the first four weeks of starting the antibiotics.