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Premenstrual Syndrome (PMS)
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Aluminum Hydroxide
Aluminum Hydroxide-containing Medications
Amiloride-containing Medications
Atenolol-containing Medications
Estradiol-containing Medications
Gentamicin-containing Medications
Quinolone Antibiotics
Tetracycline Derivatives
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Thiazide Diuretics
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Look Up > Supplements > Calcium > Interactions
Interactions with Calcium

Because calcium supplements may interfere with alendronate absorption, they should be taken two hours before or after the drug (PDR 1998).

Aluminum Hydroxide

In a study with eight male subjects, 5 mL of aluminum hydroxide gel (2.4 gm qid) coadministered with calcium citrate (950 mg qid) for three days increased urinary aluminum excretion (Coburn et al. 1991). The finding of enhanced aluminum excretion is consistent with another study involving 30 healthy women who were given calcium citrate (800 mg elemental calcium/day) (Nolan et al. 1994). Urinary and plasma aluminum levels were increased significantly. This effect may have been related to aluminum derived only from dietary sources because the women were not receiving aluminum-based antacids.


Two doses of amiloride (2.5 mg/day) reduced urinary calcium in subjects with kidney stones (Leppla et al. 1983). This decrease in calciuresis was enhanced when amiloride was coadministered with two doses of hydrochlorothiazide (25 mg/day).


Oral administration of 500 mg calcium salts (lactate, gluconate, and carbonate) with atenolol (100 mg) reduced plasma levels of atenolol by 51% in six healthy subjects (Kirch et al. 1981). Long-term coadministration increased the elimination half-life and led to atenolol accumulation. Subsequent studies did not confirm an interaction between atenolol and calcium antacids (Gugler and Allgayer 1990). Until more is known, individuals on beta-blockers should have their blood pressure checked before and after the addition of calcium antacids or supplements to their atenolol regimen.


Hypocalcemia can negate the therapeutic effects of digoxin, while hypercalcemia may predispose a patient to arrhythmias and digoxin toxicity (Hines Burnham et al. 2000). In one study, patients with digoxin-induced cardiotoxicity had serum concentrations of the drug that were within therapeutic range but they had higher calcium to potassium ratios (Sonnenblick et al. 1983). Normal levels of calcium should be maintained during digoxin treatment. Patients taking digoxin should have calcium blood levels monitored closely.

Estrogens; Progestins

Conjugated estrogens lower calcium excretion (Lobo et al. 1985) and increase calcium absorption in postmenopausal women (Gallagher et al. 1980). The enhanced absorption appears to be due to an increase in serum 1,25(OH)2D. Early postmenopausal women taking calcium supplements with estradiol (or conjugated estrogens) have been shown to have significantly greater gains in bone mineral density than women taking HRT alone (Pines et al. 1999). Calcium supplementation is highly recommended in all postmenopausal women. For women 51 years or older, the Dietary Reference Intake (DRI) for calcium is 1200 mg/day (Institute of Medicine 1997).


In a retrospective study, coronary artery bypass graft patients who received both a bypass prime with a high calcium concentration and gentamicin perioperatively had a higher incidence of renal failure compared with those who received only the prime, gentamicin alone, or neither (Schneider et al. 1996). Concomitant administration of calcium may potentiate gentamicin-induced nephrotoxicity.

Quinolone Antibiotics

Quinolone antibiotics form chelates with metal cations, such as aluminum, magnesium, calcium, iron, zinc, copper, and manganese (Kara et al. 1991; Li et al. 1999), which significantly reduces the absorption of these medications (Balfour and Wiseman 1999; Brouwers 1992; Campbell and Hasinoff 1991). Dietary supplements and antacids containing aluminum and magnesium should be taken two to four hours before or after administration of these antibiotics (Hines Burnham et al. 2000; Li et al. 1999).

Tetracycline Derivatives

Tetracyclines form chelates with divalent and trivalent cations, including iron, aluminum, magnesium, and calcium (Neuvonen 1976). These chelates are poorly soluble and can significantly reduce the absorption and efficacy of tetracyclines (Hines Burnham et al. 2000; Neuvonen 1976). Calcium salts should be administered at least two hours before or after tetracyclines (Hines Burnham et al. 2000).

Thiazide Diuretics

Thiazide diuretics may cause hypercalcemia by decreasing calcium excretion (Hines Burnham et al. 2000). Treatment with a combination of hydrochlorothiazide (50 mg/day) and vitamin D in six postmenopausal women with osteoporosis for six months reduced urinary calcium excretion by 22% (Sakhaee et al. 1984). In this study, it was noted that the combination of hydrochlorothiazide and vitamin D also decreased calcium absorption by 25%.

However, the ability of thiazide diuretics to decrease urinary calcium excretion has been associated with less risk of hip fractures in patients taking these medications (Rejnmark et al. 1998).


It has been reported that calcium salts may reverse the clinical effects and toxicities associated with verapamil (Hines Burnham et al. 2000). However, pretreatment with intravenous calcium in patients with supraventricular arrhythmias reduced the incidence of hypotensive side effects without compromising the antiarrhythmic effect of verapamil (Haft and Habbab 1986; Weiss et al. 1983). Calcium also influenced blood pressure by restoring it to control values when administered after treatment with verapamil (Weiss et al. 1983).


Balfour JA, Wiseman LR. Moxifloxacin. Drugs. 1999;57(3):363-374.

Brouwers JR. Drug interactions with quinolone antibacterials. Drug Safety. 1992;7(4):268-281.

Campbell NR, Hasinoff BB. Iron supplements: a common cause of drug interactions. Br J Clin Pharmacol. 1991;31(3):251-255.

Coburn JW MD, Mischel MG MD, Goodman WG MD, et al. Calcium citrate markedly enhances aluminum absorption from aluminum hydroxide. Amer J Kidney Dis. 1991;17(6):708-711.

Gallagher JC, Riggs BL, DeLuca HF. Effect of estrogen on calcium absorption and serum vitamin D metabolites in postmenopausal women. J Clin Endocrinol Metab. 1980;51(6):1359-1364.

Gugler R, Allgayer H. Effects on antacids on the clinical pharmacokinetics of drugs. An update. Clin Pharmacokinet. 1990;18(3): 210-219.

Haft JJ, Habbab MA. Treatment of atrial arrhythmias. Effectiveness of verapamil when preceeded by calcium infusion. Arch Intern Med. 1986; 146(6):1085-1089.

Hines Burnham T, et al, eds. Drug Facts and Comparisons. St. Louis, MO:Facts and Comparisons; 2000.

Institute of Medicine. Standing Committee on the Scientific Evaluation of Dietary Reference Intakes. Dietary Reference Intakes: Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. Washington, DC: National Academy Press; 1997.

Kara M, Hasinoff BB, McKay DW, et al. Clinical and chemical interactions between iron preparations and ciprofloxacin. Br J Clin Pharmacol. 1991;31(3):257-261.

Kirch W, Schäfer-Korting M, Axthelm T, et al. Interaction of atenolol with furosemide and calcium and aluminum salts. Clin Pharm and Ther. 1981;30(4):429-435.

Leppla D, Browne R, Hill K, Pak C. Effect of amiloride with or without hydrochlorothiazide on urinary calcium and saturation of calcium salts. J Clin Endocrinol Metab. 1983;57(5):920-924.

Li RC, Lo KN, Lam JS, et al. Effects of order of magnesium exposure on the postantibiotic effect and bactericidal activity of ciprofloxacin. J Chemother. 1999;11(4):243-247.

Lobo RA, Roy S, Shoupe D, et al. Estrogen and progestin effects on urinary calcium and calciotropic hormones in surgically-induced postmenopausal women. Horm Metab Res. 1985;17(7):370-373.

Neuvonen PJ. Interactions with the absorption of tetracyclines. Drugs. 1976;11(1):45-54.

Nolan CR, DeGoes JJ, Alfrey AC. Aluminum and lead absorption from dietary sources in women ingesting calcium citrate. South Med J. 1994;8(9):894-898.

Physicians' Desk Reference, PDR. 52nd ed. Montvale, NJ: Medical Economics Company; 1998.

Pines A, Katchman H, Villa Y, et al. The effect of various hormonal preparations and calcium supplementation on bone mass in early menopause. Is there a predictive value for the initial bone density and body weight? J Intern Med. 1999;246(4):357-361.

Rejnmark L, Mosekilde L, Andreasen F. Diuretics and osteoporosis. Nord Med. 1998 Feb;113(2):53-59.

Sakhaee K, Nicar M, Glass K, Zerwekh J, Pak C. Reduction in intestinal calcium absorption by hydrochlorothiazide in postmenopausal osteoporosis. J Clin Endocrinol Metab. 1984;59(6):1037-1043.

Schneider M, Valentine S, Clarke GM, Newman MA, Peacock J. Acute renal failure in cardiac surgical patients, potentiated by gentamicin and calcium. Anaesth Intens Care. 1996;24(6):647-650.

Sonnenblick M, Abraham AS, Meshulam Z, Eylath U. Correlation between manifestations of digoxin toxicity and serum digoxin, calcium, potassium, and magnesium concentrations and arterial pH. Br Med J. 1983;286(6371):1089-1091.

Weiss AT, Lewis BS, Halon DA, Hasin Y, Gotsman MS. The use of calcium with verapamil in the management of supraventricular tachyarrhythmias. Int J Cardiol. 1983;4(3):275-284.

Copyright © 2000 Integrative Medicine Communications

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