Effect of long term alcohol consumption on the half life of tetracycline and doxycycline in man


Elimination of the bacteriostatics tetracycline and doxycycline was compared in patients on long-term alcohol consumption to that in healthy controls. The half-life of doxycycline but not that of tetracycline was significantly shorter in alcoholics than in controls and in some patients the serum concentration of doxycycline decreased below the generally accepted minimum therapeutic concentration when dosed once daily. So, the dosing twice daily might be indicated especially if additional inducing drugs are used.

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    ABSTRACT: Monooxygenase enzymes are involved in the biotransformation of drugs and of environmental carcinogens. The activity of 7-ethoxycoumarin 0-deethylase and associated NADPH-cytochrome c reductase was determined in 9000 g supernatant from bioptically obtained liver specimens from patients with various liver diseases in order to study in vitro drug metabolising capacity. Monooxygenase and reductase activity was significantly higher in the livers of 21 patients with alcoholic liver disease (fatty liver, alcoholic hepatitis, cirrhosis of the liver) than in 22 normal controls or in six patients with chronic active hepatitis. The raised activity of drug-metabolising enzymes obtained from alcoholics with liver damage differs from normal values found in five alcoholics without liver disease. Both groups were comparable in respect to the amount of alcohol consumed and duration of abuse. A strikingly low monooxygenase activity was observed in eight patients with cirrhosis of the liver and ascites, with, however, no apparent effect on reductase activity. The results show that alcoholic liver disease is associated with enhanced monooxygenase and reductase activity, but alcoholism, per se, is not. This rise of drug-metabolising enzyme activity could lead to selectively increased rates of biotransformation in patients with alcoholic liver damage.
    Full-text · Article · Sep 1979 · Gut
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    ABSTRACT: Several conflicting observations in the literature raised considerable doubt about the metabolic fate of doxycycline, which, like other tetracyclines, has been claimed to be metabolically inert. A double liquid chromatographic approach was used in an attempt to demonstrate the polar metabolites and/or conjugates in excreta of human volunteers who ingested the drug. Both ion-exchange and reversed-phase chromatography failed to reveal significant by-products in urine and feces, except for minor amounts of 4-epidoxycycline. In addition, enzymatic hydrolysis procedures did not present any evidence of the conjugates. Thus, the different excretion behavior of doxycycline, compared to other analogs, cannot be explained in terms of increased metabolism.
    No preview · Article · Feb 1981 · Journal of Pharmaceutical Sciences
  • Article: Doxycycline
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    ABSTRACT: The chemistry, mode of action, antimicrobial activity, pharmacokinetics, and therapeutic efficacy of doxycycline are reviewed. Doxycycline displays excellent activity against gram-positive and gram-negative aerobic and anaerobic pathogens. The oral absorption of doxycycline is rapid and virtually complete and is not significantly decreased by food. Moreover, serum concentrations of doxycycline following oral and intravenous (i.v.) administration are comparable. Because of the prolonged half-life of doxycycline, once daily administration is possible. Tissue penetration of doxycycline is excellent. Levels within the therapeutic range have been found in most organs and tissues, including kidney, lung, gallbladder, prostate, intestinal tract, myocardium, sinus secretions, tonsil, aqueous humor, and female reproductive tissue. Doxycycline does not accumulate in patients with renal insufficiency and is not removed from the blood to any great extent during hemodialysis. Extensive clinical investigation has shown doxycycline to be highly effective in infections of the respiratory tract, including atypical pneumonias; skin and soft tissue; genitourinary infection including gonorrhea, syphilis, nonspecific urethritis, and prostatitis; intraabdominal infection due to trauma, sepsis, or surgery; and cholera. Evidence also suggests that doxycycline will prove effective in the treatment of Legionnaires' disease. In addition, placebo-controlled clinical trials suggest doxycycline is effective in the prevention of traveler's diarrhea.
    No preview · Article · Feb 1982 · Therapeutic Drug Monitoring
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