Alendronate is a medication used to treat and prevent osteoporosis. It works by preventing bone loss and increasing bone density, making bones stronger and reducing the risk of fractures. Common side effects include stomach pain, indigestion, and constipation. Serious side effects can include esophageal ulcers and allergic reactions. Take the medication on an empty stomach with a full glass of water, do not lie down for at least 30 minutes after taking it, and wait at least 30 minutes before eating. Avoid interactions with certain medications and regularly monitor your health while on this drug. Seek medical attention immediately if you experience severe side effects or suspect an overdose.