Azithromycin × Digoxin

Azithromycin inhibits P-glycoprotein (azithromycin SmPC). Digoxin is a P-glycoprotein substrate in the gut and kidneys, so its blood level may rise (both labels). There is a second route: in about 1 in 10 patients, gut bacteria break down 40% or more of an oral digoxin dose, and some antibiotics suppress these bacteria, so more digoxin is absorbed (US Food and Drug Administration (FDA) digoxin label). The level rises gradually as digoxin accumulates, not at once.

Nausea, anorexia, visual disturbances (yellow-green halos around lights), arrhythmias. Older patients: confusion.

The combination calls for digoxin level monitoring. Measure the serum digoxin concentration before azithromycin is started, keep monitoring and reduce the digoxin dose as needed (US Food and Drug Administration (FDA) digoxin label). During and after the azithromycin course, monitor the patient clinically and possibly the digoxin level (azithromycin SmPC). Draw the sample just before the next digoxin dose or at least 6 hours after the last one (FDA digoxin label). Older age, low body weight, reduced kidney function and electrolyte disorders raise the risk of toxicity, so these patients need monitoring most (FDA digoxin label).