Doxycycline hydroxide

These antibiotics are partially absorbed from the stomach and upper gastrointestinal tract. Food impairs absorption of all tetracyclines except doxycycline and minocycline. Absorption of doxycycline and minocy-cbne is improved with food. Since the tetracyclines form insoluble chelates with calcium (such as are found in many antacids), magnesium, and other metal ions, their simultaneous administration with milk (calcium), magnesium hydroxide, aluminum hydroxide, or iron will interfere with absorption. Because some of the tetracyclines are not completely absorbed, any drug remaining in the intestine may inhibit sensitive intestinal microorganisms and alter the normal intestinal flora. 

Bind to other drugs that are administered within 1 or 2 hours of the antacid, This process results in reduced availability of the co-administered drug for absorption, For example, the chelation of tetracyclines (e.g, tetracycline, doxycycline) will decrease their absorption by up to 90%, Avery similar process - precipitation - occurs with drugs such as quinine with aluminium and magnesium hydroxide preparations, which results in a decreased absorption of quinine, It has to be noted that the absorption of fluoroquinolones (e g. ciprofloxacin, norfloxacin, ofloxacin, enoxacin, perfloxacin i will be decreased by 60-75% if they are co-administered with divalent and trivalent cations. Patients are recommended not to take these divalent and trivalent cationic preparations until fluoroquinolone therapy is discontinued. 

Deppermann K-M, Lode H, HofQ en G, Tschink G, Kalz C, Koeppe P. Influence of ranitidine, pirenzepine, and aluminum magnesium hydroxide on the bioavailability of various antibiotics, including amoxicillin, cephalexin, doxycycline and amoxicillin-clavulanic acid. Antmdcrob Agents Chemodier( 9Z9) 33,1901-1907. 

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