Tetracyclines selectivity, basis

Doxycycline is commonly used for moderate to severe acne vulgaris. It is more effective and produces less resistance than tetracycline. The initial dose is 100 or 200 mg daily, followed by 50 mg daily as a maintenance dose after improvement is seen. Doxycycline maybe given with food, but it is more effective when taken 30 minutes before meals. / Minocycline is also commonly used for moderate to severe acne vulgaris. It is more effective than tetracycline. It is dosed similar to doxycycline (100 mg/day or 50 mg twice daily) and on an indefinite basis in selected patients. Minocycline has the most reported adverse effects of the tetracyclines, some of which may be serious. 

Minocycline is another commonly prescribed oral antibiotic used in the treatment of moderate to severe acne vulgaris. It is more effective than tetracycline because of greater lipid solubility and enhanced penetration into tissne and sebaceons foUicles. It is dosed similarly to doxycycline (100 mg/day or 50 mg twice daily) and on an indefinite basis in selected patients. 

On the basis of existing knowledge, novel quantitative approaches for the analysis of tetracyclines should involve extraction under mild acidic conditions, incorporate metalchelating agents, and investigate polymeric SPE sorbents. In addition, they should be able to detect and quantify OTC, TC, CTC, DC, and their associated 4-epimers at concentrations that are fit for their intended purpose. If confirmation is required, LC-MS/MS is recommended for its selectivity. 

The tetracyclines have been used extensively for agricultural purposes as animal feed additives however, their use has been discontinued in England on evidence of the report of the Swann committee s. This recommendation was based on findings that the bacterial flora of animals fed tetracyclines (and other antibiotics) on a continuous basis contained a high proportion of strains carrying R-factors. Such animals constitute a reservoir of resistant strains which may be passed to human subjects and possibly transmit their resistance characters to antibiotic sensitive pathogens. There is no direct evidence that such transfer occurs, but there is little doubt that the extensive use of antibiotics selects for an antibiotic-resistant population of bacteria among cattle, poultry, swine and fish which have been maintained on antibiotic feed additives . 

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