Tetracyclines semisynthetic type

The first antibiotic of the tetracycline series, chlorotetracycUne, which was isolated from a culture liquid of Streptomyces aureofaciens, was introduced into medical practice in 1948. Conseqnently, there were another six dmgs of the tetracycline series that were introdnced into medical practice between 1950 and 1972. Oxytetracycline is isolated from Streptomyces rimosus tetracycline (semisynthetic), demeclocycline is isolated from the mutant type of S. aureofaciens methacycUne (semisynthetic), doxycycUne (semisynthetic), and minocycline (semisynthetic). Methods of synthesis of the tetracycline series antibiotics have been sng-gested however, they are purely of an academic interest and do not have any practical valne. 

Tetracyclines Tetracyclines are broad spectrum antibiotics obtained from Streptomyces strains or prepared semisynthetically. Use of tetracyclines has resulted in three types of renal effects. First, the use of outdated tetracyclines results in direct proximal tubular toxicity characterized by the increased excretion of amino acids, glucose, and phosphate (Fan-coni syndrome). The mechanism of this response is unclear, but appears to be due to the formation of the degradation product anhydro-4-epi-tetracycline. Second, administration of some tetracyclines, particularly demeclocycline, can result in a dose-dependent, reversible nephrogenic diabetes insipidus, which appears to result from an inhibition of ADH effects on water reabsorption. Lastly, in patients with preexisting compromised renal function, tetracyclines can induce increased sodium excretion and azotemia. The mechanism of the naturesis may be due to an effect of tetracyclines on luminal membrane sodium conductance, while the azotemia appears to result from the antianabolic effects of the tetracyclines. 

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