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Risedronate

Also indexed as: Actonel™

Risedronate is used to treat Paget’s disease of the bone, and is in a family of drugs known as bisphosphonates.

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.

Summary of Interactions for Risedronate

Depletion or interference Calcium*
Adverse interaction None known
Side effect reduction/prevention None known
Supportive interaction None known
Reduced drug absorption/bioavailability Antacids
Calcium
Food
Iron
Magnesium
Zinc (absorption)
Zinc (action)

For the convenience of the reader, the information in the summary is categorized as follows: “Depletion or interference” indicates the drug may deplete or interfere with the absorption or function of the supplement or herb. “Adverse interaction” indicates that the supplement or herb used together with the drug may result in undesirable effects. “Side effect reduction/prevention” indicates the supplement or herb may reduce the likelihood and/or severity of a potential side effect caused by the drug. “Supportive interaction” indicates the supplement or herb may support or aid the function of the drug. “Reduced drug absorption/bioavailability” indicates that the supplement or herb may decrease the absorption and/or activity of the drug in the body. An asterisk (*) next to an item in the summary indicates that the interaction is supported only by weak, fragmentary, and/or contradictory scientific evidence.

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.