Orient Calcium Lactate I.p. 25 gm Calcium can decrease the absorption of other drugs such as bisphosphonates (for example, alendronate), tetracycline antibiotics (such as doxycycline, minocycline), estramustine, levothyroxine, and quinolone antibiotics (such as ciprofloxacin, levofloxacin). Therefore, separate your doses of these medications as far as possible from your doses of calcium. Ask your doctor or pharmacist about how long you should wait between doses and for help finding a dosing schedule that will work with all your medications.