Alendronic acid osteoporosis drug. Single tablet of the osteoporosis drug alendronic acid. This drug is used to treat and prevent osteoporosis in post-menopausal women. It belongs to a class of drugs called bisphosphonates. It inhibits the action of bone cells that degrade and reabsorb bone (osteoclasts), therefore slowing the loss of bone mass. One tablet is taken once a week. It is important to take alendronic acid while upright and with plenty of water as it can cause inflammation and ulceration of the oesophagus