chelation
11 interactions related to chelation
doxycycline + iron
Iron forms an insoluble chelate complex with doxycycline in the gut, sharply reducing absorption of the antibiotic. In controlled human studies, ferrous sulfate taken together with doxycycline cut serum antibiotic levels substantially, which can undermine treatment.
doxycycline + magnesium
Magnesium ions can bind doxycycline in the gastrointestinal tract, forming a poorly absorbed complex that reduces how much antibiotic reaches the bloodstream. Magnesium-containing supplements, antacids, and laxatives can meaningfully lower doxycycline absorption if taken at the same time.
doxycycline + calcium
Calcium binds doxycycline in the gut, forming a complex the body cannot fully absorb. Taking doxycycline together with calcium supplements, calcium-based antacids, or large dairy servings can lower how much antibiotic reaches the bloodstream, though doxycycline binds calcium less than older tetracyclines.
risedronate + calcium
Calcium and other divalent cations bind risedronate in the gut and form insoluble complexes, blocking absorption of a drug whose oral bioavailability is already very low. Taking them together can reduce the absorbed amount to subtherapeutic levels and quietly undermine osteoporosis treatment.
tetracycline + zinc
Zinc forms a chelate with tetracycline in the gastrointestinal tract, modestly reducing absorption of the antibiotic. The interaction also reduces zinc absorption. Doxycycline is much less affected.
tetracycline + calcium
Calcium binds to tetracycline in the gut, forming an insoluble chelate that the intestine cannot absorb. Dairy products, calcium supplements, and calcium-based antacids can sharply reduce how much tetracycline reaches your bloodstream, which can drop levels below what is needed to treat the infection.
phenytoin + calcium
Calcium-containing supplements and antacids can bind phenytoin in the gut and lower how much of the drug is absorbed when the two are taken together, which can reduce phenytoin's blood level. Separately, long-term phenytoin use can reduce calcium absorption by speeding up the breakdown of vitamin D, which is relevant to bone health over time.
alendronate + calcium
Calcium binds alendronate in the gut and forms an insoluble complex, sharply reducing absorption of an already very poorly absorbed bisphosphonate. Taken together, the calcium can leave the osteoporosis drug clinically ineffective.
levofloxacin + calcium
Calcium binds (chelates) levofloxacin in the gastrointestinal tract, modestly lowering the antibiotic's peak blood level. Total drug exposure over the dosing interval is largely preserved, so the effect is smaller than with iron, magnesium, or aluminum. Separating the doses by a couple of hours avoids the interaction.
dairy + fluoroquinolones
Calcium and other metal ions in dairy products bind oral fluoroquinolone antibiotics in the gut, forming poorly absorbed chelate complexes that lower the amount of antibiotic reaching the bloodstream.
whey protein + iron
Whey protein is usually consumed alongside calcium-rich milk minerals, and calcium competes with iron for absorption in the gut. When taken at the same time, a whey-plus-iron serving can modestly lower how much iron you absorb. The effect is largely driven by calcium, is generally modest, and is easily offset by taking a vitamin C source with your iron.