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Author: Admin | 2025-04-28
Erythromycin may occur.WarfarinInitiation of erythromycin therapy in some patients stabilized on warfarin has resulted in prolongation of prothrombin time and bleeding. Increased anticoagulant effect may be more pronounced in geriatric patients. The exact mechanism(s) of this interaction has not been clearly established, but erythromycin may inhibit hepatic metabolism of warfarin. Prothrombin time should be monitored more closely than usual in patients receiving warfarin when erythromycin therapy is initiated, and warfarin dosage should be adjusted as necessary. Laboratory Test InterferencesErythromycin may falsely elevate concentrations of urinary catecholamines, 17-hydroxycorticosteroids, and 17-ketosteroids. The drug may interfere with colorimetric assays resulting in falsely increased AST (SGOT) and ALT (SGPT) concentrations. Falsely elevated AST concentrations without liver injury may result due to erroneous measurement of unidentified metabolites of erythromycin in colorimetric determinations.Erythromycin may decrease serum folate assay results if a microbiologic method is used since the drug can inhibit the growth of Lactobacillus casei; results are unaffected if the chromatographic procedure of Landon is used. The presence of erythromycin in the blood may interfere with the etiologic diagnosis of mycoplasmal pneumonia by masking a rise in the titer of the tetrazolium reduction inhibition neutralizing antibody to Mycoplasma pneumoniae.Mechanism of ActionErythromycin is usually bacteriostatic, but it may be bactericidal in high concentrations or against highly susceptible organisms.Erythromycin inhibits protein synthesis in susceptible organisms by binding to 50S ribosomal subunits, thereby inhibiting translocation of aminoacyl transfer-RNA and inhibiting polypeptide synthesis. The site of action of erythromycin is the same as that of other macrolides (e.g., azithromycin, clarithromycin) and the same as that of clindamycin, lincomycin, and chloramphenicol.Erythromycin exerts its effect only against multiplying organisms. Only un-ionized erythromycin is believed to penetrate susceptible bacteria, and penetration increases in an alkaline environment as the pKa of the drug is approached. Erythromycin generally penetrates the cell wall of gram-positive bacteria more readily than that of gram-negative bacteria, and gram-positive organisms may accumulate 100 times more erythromycin than do gram-negative organisms.SpectrumErythromycin is active in vitro against gram-positive cocci (staphylococci and streptococci) and gram-positive bacilli including Bacillus anthracis, Corynebacterium, Clostridium, Erysipelothrix, and Listeria monocytogenes. Erythromycin also is active in vitro against some
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