The structural alterations to the erythromycin base used to synthesize the advanced macrolides and ketolides result in improved pharmacokinetic properties. Because erythromycin is degraded in an acidic environment, oral bioavailability is variable and depends on the preparation studied. Clari- thromycin and azithromycin are more acid-stable and have greater oral bioavailability (55% and 37%, respectively) [14,15]. When taken with meals the peak plasma concentration of clarithromycin immediate-release tablets is increased by 24% but the overall bioavailability is unchanged [16]. Clarithromycin extended-release tablets provide extended absorption of clarithromycin from the gastrointestinal tract. The bioavailability of the extended-release formulation is equivalent to the immediate-release tablets when taken with food but is decreased by 30% when administered in the fasting state [17]. The extended-release formulations of clarithromycin should be administered with food, whereas the immediate-release tablets can be taken with or without food. The oral bioavailability of the
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