chelation
11 interactions related to chelation
doxycycline + iron
Iron forms an insoluble chelate complex with doxycycline in the gastrointestinal tract, dramatically reducing absorption of the antibiotic. Studies show ferrous sulfate co-administration can lower doxycycline serum levels by 80% or more, potentially leading to treatment failure.
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 (~0.6%). Co-administration can reduce the dose to subtherapeutic levels.
tetracycline + zinc
Zinc forms a chelate with tetracycline in the gastrointestinal tract, reducing absorption of the antibiotic by approximately 30 percent. The interaction also reduces zinc absorption.
tetracycline + calcium
Calcium binds tightly to tetracycline in the gut, forming an insoluble chelate that cannot be absorbed. Dairy products and calcium supplements can reduce tetracycline absorption by 50 to 90 percent, often dropping serum levels below the threshold needed to treat infection.
doxycycline + calcium
Calcium chelates doxycycline in the gut, forming an insoluble complex that cannot be absorbed. Co-administration with calcium supplements or dairy products can reduce doxycycline absorption by 50 to 80 percent.
phenytoin + calcium
Phenytoin reduces calcium absorption by accelerating vitamin D catabolism and by directly inhibiting active transcellular calcium transport in intestinal enterocytes; separately, calcium-containing antacids and supplements can chelate phenytoin in the gut and lower its absorption when taken simultaneously.
alendronate + calcium
Calcium binds alendronate in the gut and forms an insoluble chelate, drastically reducing absorption of an already poorly bioavailable bisphosphonate (oral bioavailability is only ~0.6%). Co-administration can render the osteoporosis drug clinically ineffective.
levofloxacin + calcium
Calcium chelates levofloxacin in the gastrointestinal tract, reducing peak serum concentrations by 20 to 30 percent. While the area under the curve is less affected than with older fluoroquinolones, the drop in peak concentration can matter for organisms with MICs close to the breakpoint.
doxycycline + magnesium
Magnesium ions chelate doxycycline in the gastrointestinal tract, forming an insoluble complex that markedly reduces antibiotic absorption. Magnesium-containing antacids and supplements can lower doxycycline bioavailability by up to 90 percent.
dairy + fluoroquinolones
Calcium and magnesium in dairy products chelate with fluoroquinolone antibiotics (ciprofloxacin, levofloxacin, moxifloxacin) in the gut, forming insoluble complexes that the body cannot absorb. Co-ingestion can reduce fluoroquinolone bioavailability by 30-50%, potentially causing treatment failure.
whey protein + iron
Whey protein contains calcium and bioactive peptides that can chelate iron in the gut and reduce its absorption. Studies in iron-fortified casein-whey drinks show calcium added with whey reduces iron absorption by approximately 18 to 27 percent.