Food has the following effects on macrolide absorption: For extended-release clarithromycin, increased absorption For immediate-release clarithromycin tablet or suspension, no effect For azithromycin capsules and erythromycin (including base and stearate formulations), decreased absorption For fidaxomicin, minimal effects Once absorbed macrolides diffuse well into body fluids, except cerebrospinal fluid, and are concentrated in phagocytes.