Medscape -- The US Food and Drug Administration (FDA) has approved safety labeling revisions to advise that concomitant use of azithromycin may potentiate the effects of oral anticoagulants, frovatriptan succinate is linked to a risk for serotonin syndrome that is increased by coadministration of antidepressants, and regadenoson injection may cause heart block and hypotension in some patients.