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By Joan Unger, RN, MS, ARNP and James Chan, PharmD, PhD
Merck & Co. has received Food and Drug Administration (FDA) approval to market once-a-week doses of alendronate (marketed under the trade name Fosamax) for the treatment and prevention of osteoporosis. Alendronate is a bisphosphonate that inhibits bone resorption. It has been available since 1995 as a once-a-day medication and has been widely used to treat and prevent osteoporosis in postmenopausal women. Alendronate inhibits the rate and extent of bone resorption by inhibiting osteoclast activity. The drug has a long half-life on bone surface, which allows for weekly dosing. In a comparative one-year study, 70 mg once weekly was as effective as 10 mg daily. Increases in bone mineral density (BMD) in the lumbar spine in those who completed the trial were 5.1% and 5.4% for the weekly and daily dosing respectively.1,2 Increases in BMD at the total hip, femoral neck, trochanter, and total body were similar. Weekly and daily regimens appear to be comparable in efficacy as shown by BMD studies. In a one-year prevention trial, alendronate, 35 mg weekly and 5 mg daily, produced a 2.9% and 3.2% increase in BMD, respectively.1
Long-term studies on fracture rates have not been conducted with the weekly regimens. While complaints such as dyspepsia and abdominal pain have been associated with alendronate administration, the drug did not appear to be associated with serious upper gastrointestinal (GI) events in patients with no recent history of GI events.3
The dose of alendronate for the treatment of osteoporosis is 70 mg once weekly. For prevention, the dose is 35 mg once weekly. Alendronate is not recommended for patients with renal impairment (creatinine clearance < 35 mL/min).1 Cost of the daily and weekly regimens is the same.
• Nursing considerations.
Weekly alendronate 35 mg and 70 mg provide an alternative to the daily regimens for the prevention and treatment of osteoporosis and may be preferred by patients who cannot tolerate the daily dose or cannot follow the strict regimen. It also may improve compliance as patients need only follow the instructions once weekly instead of daily. Once-weekly dosing also reduces esophageal exposure to the drug. A trend toward a lower incidence of esophageal or gastric duodenal irritation was seen with the weekly dosing compared to daily dosing.2
Patients must take alendronate with specific instructions to reduce esophageal irritation. A retrospective database analysis reported that patients taking alendronate and who are elderly or are users of nonsteroidal anti-inflammatory drugs may have a greater risk of clinic visits and hospital admissions for acid-related GI disorders.4
• Patient education.
Alendronate should be taken upon rising with plain water (6-8 oz) at least one-half hour before the first food, beverage, or medication of the day. Patients should not lie down for at least 30 minutes and until after their first food of the day.1 Patients also should receive supplemental calcium and vitamin D if they are not adequately supplied by the diet. Advise patients not to chew or suck on the tablets, as this may cause oropharyngeal ulceration. If they miss a dose, advise patients to take it the next morning after they remember and return to the originally chosen weekly schedule.
1. Fosamax Product Information. Merck & Co. October 2000.
2. Schnitzer T, et al. Aging Clin Exp Res 2000; 12:1-12.
3. Bauer DC, et al. Arch Intern Med 2000; 160:517-525.
4. Ettinger B, et al. Am J Manag Care 1998; 4:1,377-1,382. n