Osteoporosis happens when not enough new bone grows to replace the bone that is naturally broken down. Gradually, the bones become thin and fragile, and more likely to break. Osteoporosis is more common in women after the menopause, when the levels of the female hormone oestrogen fall, since oestrogen helps to keep bones healthy.

Vantavo contains two active substances: alendronic acid and colecalciferol (vitamin D3). Alendronic acid is a bisphosphonate that has been used in osteoporosis since the mid-1990s. It slows the action of the osteoclasts, the cells that are involved in breaking down the bone tissue. Blocking the action of these cells leads to less bone loss. Vitamin D3 is a nutrient that is found in some foods, but is also made in the skin through exposure to natural sunlight. Vitamin D3, along with other forms of vitamin D, is required for calcium absorption and normal bone formation. Since patients with osteoporosis may not get enough vitamin D3 through exposure to sunlight, it is included in Vantavo.