alendronate

Alendronate is a nitrogen-containing bisphosphonate used to prevent and treat osteoporosis in postmenopausal women and in men, to treat glucocorticoid-induced osteoporosis, and to manage Paget's disease of bone. It works by inhibiting osteoclast-mediated bone resorption through suppression of the farnesyl pyrophosphate synthase enzyme in the mevalonate pathway, which leads to osteoclast dysfunction and reduced bone turnover. The result is increased bone mineral density and a decreased risk of vertebral and nonvertebral fractures.

Administration and dosing commonly involve oral tablets taken with a full glass of plain water, first thing in the morning, at least 30 minutes before food, drinks, or other medications. The patient should remain upright for at least 30 minutes after taking the dose to reduce the risk of esophageal irritation. Dosing regimens vary by indication and country, with examples including once-weekly and daily schedules (for example, a weekly regimen of 70 mg or a daily regimen of 10 mg for osteoporosis; other regimens exist for glucocorticoid-induced osteoporosis and Paget’s disease).

Contraindications include esophageal abnormalities or motility disorders, inability to sit or stand upright for at least 30 minutes, hypersensitivity to the drug, and hypocalcemia. Pregnancy is discouraged, and renal impairment may necessitate dose adjustments or avoidance. Caution is advised in patients with low calcium or vitamin D levels, renal disease, or significant dental disease.

Common adverse effects are gastrointestinal symptoms (esophagitis, abdominal pain, reflux), musculoskeletal pain, and rare but serious events such as osteonecrosis of the jaw and atypical femoral fractures with long-term use. Potential drug interactions include calcium, antacids, and iron supplements, which can impair absorption; these should be spaced from alendronate administration. Monitoring typically includes bone density testing, calcium and vitamin D status, renal function, and dental evaluation as appropriate.