Risedronate

Summary of Interactions with Vitamins, Herbs, and Foods
(for details about the summarized interactions, read the full article)

May be Beneficial: Depletion or interference—The medication may deplete or interfere with the absorption or function of the nutrient. Taking these nutrients may help replenish them.	Calcium*
Avoid: Reduced drug absorption/bioavailability—Avoid these supplements when taking this medication since the supplement may decrease the absorption and/or activity of the medication in the body.	Antacids Calcium Food Iron Magnesium Zinc (absorption) Zinc (action)
Side effect reduction/prevention	None known
Supportive interaction	None known
Adverse interaction	None known

Interactions with Dietary Supplements

Calcium and Vitamin D
Short-term treatment with risedronate in people with hyperparathydoidism—a disorder characterized by high blood levels of calcium—resulted in lower calcium blood levels.¹ Additional research is needed to determine whether people taking risedronate for Paget’s disease might develop low blood calcium levels. As a precaution, people with Paget’s disease should take supplemental calcium and vitamin D if dietary intake is inadequate. However, taking risedronate at the same time as calcium supplements reduces absorption of the drug.² Therefore, people taking risedronate for Paget’s disease should take calcium supplements an hour before or two hours after taking the drug.

Minerals
Taking risedronate at the same time as iron, zinc, or magnesium may reduce the amount of drug absorbed.³ Therefore, people taking risedronate who wish to supplement with these minerals should take them an hour before or two hours after the drug.

Interactions with Foods and Other Compounds

Antacids
Taking risedronate at the same time as antacids containing calcium or magnesium may reduce absorption of the drug. Therefore, people taking risedronate should take calcium- or magnesium-containing antacids an hour before or two hours after the drug.

Food
One controlled study showed that taking risedronate either a half an hour before or two hours after a meal dramatically reduced absorption of the drug, compared with taking the drug one hour before or four hours after a meal.⁴ Consequently, people should take risedronate one hour before a meal or 4 hours after a meal, as long as the latter is at least one hour before the next meal.

References

1. Reasner CA, Stone MD, Hosking DJ, et al. Acute changes in calcium homeostasis during treatment of primary hyperparathyroidism with risedronate. J Clin Endocrinol Metab 1993;77:1067–71.

2. Sifton DW, ed. Physicians’ Desk Reference. Montvale, NJ: Medical Economics Company, Inc., 2000, 2504–6.

3. Sifton DW, ed. Physicians’ Desk Reference. Montvale, NJ: Medical Economics Company, Inc. 2000, 2504–6.

4. Mitchell DY, Heise MA, Pallone KA, et al. The effect of dosing regimen on the pharmacokinetics of risedronate. Br J Clin Pharmacol 1999;48:536–42.

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The information presented in Healthnotes is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over-the-counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires March 2005.