title: Factors affecting the in-vitro activity of roxithromycin.
abstract: The effect of human serum and CO2 on the activity of roxithromycin and erythromycin was assessed. Protein binding of roxithromycin in serum from various animal sources, acid alpha 1-glycoprotein and human albumin V was determined. There was a four- to eight-fold increase in MIC and MBC of roxithromycin in the presence of 70 and 100% human serum (minimum effect seen with erythromycin) and for both compounds there was a four- to eight-fold increase in MIC for fastidious organisms in the presence of CO2. Roxithromycin appears to be selectively bound to acid alpha 1-glycoprotein, binding decreases with an increase in roxithromycin concentration (saturable at 10 mg/l) and protein binding is variable depending on animal source (86% human, 10% guinea pig) and this must be considered when data on activity from animal studies are evaluated.
mesh_terms: D000818:Animals; D001412:Bacillus subtilis / Q000187:drug effects; D001419:Bacteria / Q000187:drug effects*; D004917:Erythromycin / Q000494:pharmacology; D006168:Guinea Pigs; D006801:Humans; D007933:Leucomycins / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D009961:Orosomucoid / Q000378:metabolism; D011485:Protein Binding; D011817:Rabbits; D051381:Rats; D012505:Sarcina / Q000187:drug effects; D012709:Serum Albumin / Q000378:metabolism; D013045:Species Specificity; D013552:Swine
chemical_list: D007933:Leucomycins; D009961:Orosomucoid; D012709:Serum Albumin; D004917:Erythromycin