Does Fosamax (alendronate) alter calcium levels?

From the Guidelines

Fosamax (alendronate) does not significantly alter calcium levels in the blood when used as prescribed. Alendronate belongs to the bisphosphonate class of medications that work by inhibiting bone resorption by osteoclasts, which helps maintain bone density and strength. While the medication affects calcium metabolism in bones, it does not typically cause meaningful changes in serum calcium concentrations in patients with normal kidney function and adequate calcium intake 1. However, to ensure optimal bone health while taking Fosamax, patients should maintain adequate calcium and vitamin D intake, typically 1000-1200 mg of calcium and 800-1000 IU of vitamin D daily. This supplementation is important because Fosamax works best when the body has sufficient calcium available for bone mineralization.

Key Considerations

• Patients should have serum calcium measured prior to starting treatment 1.
• Calcium and vitamin D supplementation is recommended unless otherwise contraindicated 1.
• Oral bisphosphonates and calcium should not be taken concurrently; several monographs suggest an interval of at least 2 hours to allow for maximum absorption 1. Patients should take Fosamax first thing in the morning with plain water, at least 30 minutes before any food, beverage, or other medications, and remain upright for at least 30 minutes afterward to prevent esophageal irritation.

Important Warnings

• Hypocalcemia is a contraindication for some bisphosphonates, including Alendronate/cholecalciferol (Fosamax Plus D) and Zoledronic acid (Reclast) 1.
• Patients receiving intravenous bisphosphonates (zoledronic acid) should be monitored for renal function prior to starting this treatment, and for serum calcium and increase in serum creatinine throughout the treatment period 1.

From the FDA Drug Label

As a result of inhibition of bone resorption, asymptomatic reductions in serum calcium and phosphate concentrations were also observed following treatment with alendronate sodium In the long-term studies, reductions from baseline in serum calcium (approximately 2%) and phosphate (approximately 4 to 6%) were evident the first month after the initiation of alendronate sodium 10 mg. No further decreases in serum calcium were observed for the five-year duration of treatment; however, serum phosphate returned toward prestudy levels during years three through five As a result of the inhibition of bone resorption, alendronate sodium induced generally mild, transient, and asymptomatic decreases in serum calcium and phosphate Presumably due to the effects of alendronate sodium on increasing bone mineral, small, asymptomatic decreases in serum calcium and phosphate may occur, especially in patients with Paget's disease, in whom the pretreatment rate of bone turnover may be greatly elevated and in patients receiving glucocorticoids, in whom calcium absorption may be decreased

Yes, Fosamax (alendronate) can alter calcium levels, with asymptomatic reductions in serum calcium concentrations observed in patients treated with the medication 2. These reductions are generally mild and transient 2.

From the Research

Fosamax and Calcium Levels

• Fosamax (alendronate) can alter calcium levels, as evidenced by a study where a patient developed hypocalcemia after treatment with alendronate 3.
• The study suggests that patients with unexplained hypocalcemia should be screened for celiac sprue, even in the absence of gastrointestinal symptoms 3.
• Another study found that alendronate decreased plasma calcium levels in normal rats, primarily by suppressing bone resorption 4.
• However, a study on postmenopausal women with low bone mineral density found that treatment with alendronate plus calcium, alendronate alone, or calcium alone resulted in significant increases in bone mineral density, with no significant difference in calcium levels between the groups 5.
• A study on HIV-infected patients found that alendronate, vitamin D, and calcium supplementation increased lumbar spine bone mineral density, with no significant adverse effects on calcium levels 6.

Mechanism of Action

• Alendronate decreases plasma calcium levels by suppressing bone resorption, whereas other medications like elcatonin decrease plasma calcium by inhibiting bone resorption and accelerating calcium excretion 4.
• Bisphosphonates like alendronate and ibandronate inhibit artery calcification at doses comparable to those that inhibit bone resorption, without affecting serum calcium and phosphate levels 7.