Minor
Doxycycline × Iron oral (salts: sulfate, bisglycinate, fumarate, gluconate, polymaltose; heme iron polypeptide, lactoferrin)
Tetracyclines×Oral iron preparations; antianaemic agents
Mechanism
Iron forms non-absorbable chelates with tetracyclines in the gut (as with the doxycycline-calcium pair). Doxycycline bioavailability falls by 50–80%.
Symptoms
Persistent infection symptoms 48–72 hours after antibiotic start, risk of clinical failure.
Management
Take doxycycline 2 hours before or 6 hours after iron supplements. Same interval applies to calcium, magnesium, zinc, and aluminium-containing antacids. If timing separation is impossible (e.g. severe iron deficiency), choose an alternative antibiotic (amoxicillin, a cephalosporin).
Check the full regimen, not just this pair
Opens the checker with these two drugs prefilled. Add the rest of the regimen and recompute additive risks.