Moderate
Azithromycin × Digoxin
Macrolides×Cardiac glycosides (digitalis)
Mechanism
Macrolides suppress the gut bacteria Eggerthella lenta that inactivate digoxin. Digoxin plasma levels rise within days of co-administration.
Symptoms
Nausea, anorexia, visual disturbances (yellow-green halos around lights), arrhythmias. Older patients: confusion.
Management
For short azithromycin courses (3–5 days), check digoxin level at 5–7 days. If it rises, temporarily reduce digoxin. Alternative antibiotics without gut flora effect: a cephalosporin or doxycycline.