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This information is listed deep in the archives in a previous post, but since I am reading posts by so many new members who are taking doxycycline (or minocycline), I thought I would bring it up again. If you are taking doxycycline or any of the other tetracyclines, please be aware that calcium supplements interfere with the effectiveness of the antibiotic. Also, anyone taking thyroid medications, please be aware that calcium supplements interfere with thyroid medications as well.
http://ods.od.nih.gov/factsheets/calcium.asp
http://www.uspharmacist.com/index.as...age=8_1933.htm
http://ods.od.nih.gov/factsheets/calcium.asp
Calcium supplements have the potential to interact with several prescription and over the counter medications. Further information about these interactions is described below. Some examples of medications that may interact with calcium include:
* digoxin
* fluroquinolones
* levothyroxine
* antibiotics in tetracycline family
* tiludronate disodium
* anticonvulsants such as phenytoin
* thiazide, type of diuretic
* glucocorticoids
* mineral oil or stimulant laxatives
* aluminum or magnesium containing antacids
Calcium supplements may decrease levels of the drug digoxin, a medication given to heart patients [112]. The interaction between calcium and vitamin D supplements and digoxin may also increase the risk of hypercalcemia. Calcium supplements also interact with fluoroquinolones (a class of antibiotics including ciprofloxacin), levothyroxine (thyroid hormone) used to treat thyroid deficiency, antibiotics in the tetracycline family, tiludronate disodium (a drug used to treat Paget's disease), and phenytoin (an anti-convulsant drug). In all of these cases, calcium supplements decrease the absorption of these drugs when the two are taken at the same time [112,113].
* digoxin
* fluroquinolones
* levothyroxine
* antibiotics in tetracycline family
* tiludronate disodium
* anticonvulsants such as phenytoin
* thiazide, type of diuretic
* glucocorticoids
* mineral oil or stimulant laxatives
* aluminum or magnesium containing antacids
Calcium supplements may decrease levels of the drug digoxin, a medication given to heart patients [112]. The interaction between calcium and vitamin D supplements and digoxin may also increase the risk of hypercalcemia. Calcium supplements also interact with fluoroquinolones (a class of antibiotics including ciprofloxacin), levothyroxine (thyroid hormone) used to treat thyroid deficiency, antibiotics in the tetracycline family, tiludronate disodium (a drug used to treat Paget's disease), and phenytoin (an anti-convulsant drug). In all of these cases, calcium supplements decrease the absorption of these drugs when the two are taken at the same time [112,113].
Calcium interacts with prescription medications by limiting their absorption through chelation. Significant interactions have been observed between calcium and certain antibiotics--namely tetracyclines and fluoroquinolones. Calcium carbonate can reduce the bioavailability of ciprofloxacin by 40%, which could result in inadequate infection treatment and increased complications.15 Patients taking tetracyclines or fluoroquinolones should avoid the supplement altogether during the course of therapy, which is usually a short period of time.16,17
Typically, pharmacists will instruct patients to space the doses of medications and/or supplements whose absorption is affected by binding. Controversy, however, exists on how much time is long enough to wait between doses. A minimum of two hours is usually mandated, with some sources citing four to six hours as a minimum recommendation. For example, it is recommended that doses of calcium and levothyroxine be separated by at least four hours, because the former decreases the bioavailability of the latter.18
Typically, pharmacists will instruct patients to space the doses of medications and/or supplements whose absorption is affected by binding. Controversy, however, exists on how much time is long enough to wait between doses. A minimum of two hours is usually mandated, with some sources citing four to six hours as a minimum recommendation. For example, it is recommended that doses of calcium and levothyroxine be separated by at least four hours, because the former decreases the bioavailability of the latter.18