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Cardiovascular Medications
Cardiac Glycosides


Digoxin increases the renal excretion of magnesium (Schwinger and Erdmann 1992). Low magnesium concentrations increase cardiac glycoside toxicity.

Significance of Depletion

Magnesium deficiency affects calcium and vitamin D metabolism and is primarily associated with hypocalcemia (Cashman and Flynn 1999). Clinically, neuromuscular hyperexcitability may be the first symptom manifested in patients with hypomagnesemia (reflected in a serum concentration of 17 mg/L or less). Recent evidence supports a possible connection between chronically low magnesium levels and various illnesses such as cardiovascular disease, hypertension, diabetes, and osteoporosis.

Replacement Therapy

The current recommended dietary allowance (RDA) for magnesium ranges from 30 to 420 mg/day, depending upon age and gender (Cashman and Flynn 1999). For replacement therapy, doses should be tailored to the patient's clinical condition, taking into account serum magnesium levels, dietary habits, and medication regimen.

Vitamin B1 (Thiamine)

Digoxin inhibits thiamine uptake by cardiac cells; chronic use may cause a deficiency of this nutrient (Zangen et al. 1998).

Significance of Depletion

Early nonspecific manifestations of depleted thiamine levels include weakness, fatigue, anorexia, constipation, nystagmus, and mental status changes such as memory loss, confusion, and depression (Covington 1999). Beriberi is the classic condition associated with thiamine deficiency. Symptoms include polyneuritis, cardiac disturbances (bradycardia, heart failure, hypertrophy), and possibly edema. Thiamine deficiency rarely occurs alone; it is usually accompanied by deficiencies in other B vitamins.

Replacement Therapy

Although the recommended daily allowance (RDA) for this nutrient ranges from 1.1 to 1.5 mg for adults depending on gender, treatment of beriberi requires oral doses as high as 5 to 10 mg/day for one month to achieve tissue saturation and replenish body stores of thiamine (Covington 1999). Treatment of deficiency secondary to alcoholism may require up to 40 mg/day of thiamine orally; cardiovascular disease may warrant a total daily intake of 90 mg (Marcus and Coulston 1996). Replacement therapy should be tailored to the patient's needs depending on age, gender, clinical presentation, serum vitamin B1 levels, dietary habits, and medication regimen.

Editorial Note

This information is intended to serve as a concise reference for healthcare professionals to identify substances that may be depleted by many commonly prescribed medications. Depletion of these substances depends upon a number of factors including medical history, lifestyle, dietary habits, and duration of treatment with a particular medication. The signs and symptoms associated with deficiency may be nonspecific and could be indicative of clinical conditions other than deficiency. The material presented in these monographs should not in any event be construed as specific instructions for individual patients.


Cashman K, Flynn A. Optimal nutrition: calcium, magnesium and phosphorus. Proc Nutr Soc. 1999;58:477-487.

Covington T, ed. Nonprescription Drug Therapy Guiding Patient Self-Care. St Louis, MO: Facts and Comparisons; 1999:467-545.

Marcus R, Coulston AM. Water-soluble vitamins. In: Hardman JG, Limbird LE, et al, eds. Goodman & Gilman's The Pharmacological Basis of Therapeutics. 9th ed. New York, NY: McGraw-Hill Health Professions Division; 1996:1557-1558.

Schwinger RH, Erdmann E. Heart failure and electrolyte disturbances. Methods Find Exp Clin Pharmacol. 1992;14(4);315-325.

Zangen A, Botzer D, Zangen R, Shainberg A. Furosemide and digoxin inhibit thiamine uptake in cardiac cells. Eur J Pharmacol. 1998;61(1):151-155.

Copyright © 2000 Integrative Medicine Communications

This publication contains information relating to general principles of medical care that should not in any event be construed as specific instructions for individual patients. The publisher does not accept any responsibility for the accuracy of the information or the consequences arising from the application, use, or misuse of any of the information contained herein, including any injury and/or damage to any person or property as a matter of product liability, negligence, or otherwise. No warranty, expressed or implied, is made in regard to the contents of this material. No claims or endorsements are made for any drugs or compounds currently marketed or in investigative use. The reader is advised to check product information (including package inserts) for changes and new information regarding dosage, precautions, warnings, interactions, and contraindications before administering any drug, herb, or supplement discussed herein.