Risedronate (Actonel), a new bisphosphonate, was launched on April 12. The drug is being jointly marketed by Procter & Gamble and Aventis (see p635). It is licensed to reduce risk of vertebral fracture in established postmenopausal osteoporosis, to prevent osteoporosis in postmenopausal women with increased risk of osteoporosis and to maintain or increase bone mass in post-menopausal women undergoing long-term systemic corticosteroid treatment. The drug is also licensed for the treatment of Paget's disease.
Speaking at the launch, Professor David Reid (professor of rheumatology, University of Aberdeen) said that risedronate gave a rapid reduction in vertebral fracture risk, in excess of 60 per cent in the first year of treatment. This effect was sustained over three years.
Professor Reid reported the results of phase III clinical trials in which the prevention of vertebral fracture was examined in 3,684 postmenopausal women. Risedronate was found to be effective "right across the board in the first year". In the US, treatment resulted in a 74 per cent reduction in vertebral fractures in high risk women and a 65 per cent reduction in other women. In Europe, the corresponding figures were 65 and 61 per cent. In patients with corticosteroid-induced osteoporosis, risedronate gave a 73 per cent reduction in fracture rate. There was no evidence that risedronate caused dyspeptic symptoms, Professor Reid said.
The manufacturer's summary of product characteristics for Actonel includes digestive system reactions among "possible" or "probable" adverse effects noted in trials. However, it also says that most reported adverse effects were mild to moderate in severity and usually did not require cessation of therapy.
Dr Robert Lindsay (professor of clinical medicine, Columbia university, New York, US), said that it was now realised that osteoporosis was a disease that needed urgent intervention. One vertebral fracture hastened the likelihood of another occurring. This was known as the "domino effect". New data to be presented at the European Calcified Tissues Symposium in Finland in May would show that one in five osteoporotic women with vertebral fracture could suffer another vertebral fracture within 12 months. "The data confirm the need to diagnose and intervene in postmenopausal osteoporosis early and to treat it with a medication which will act quickly and halt disease progression," Dr Lindsay said.
Professor Graham Russell (department of human metabolism and clinical biochemistry, University of Sheffield) said that, in terms of effects on bones, there were more similarities than differences between risedronate and the other bisphosphonates. However, he pointed out that gastrointestinal effects were perceived as a problem with alendronate which was why the clinical trials for risedronate had included patients with gastrointestinal disease.
Professor Russell also suggested that the fast action of risedronate distinguished it from other drugs in the group but he acknowledged that there had been no head to head trials comparing the bisphosphonates. Mrs Linda Edwards (director, National Osteoporosis Society) welcomed the launch of risedronate. She said that, while the NOS was unbiased between treatments, it was "good news that there are more therapies available to treat osteoporosis and stop fractures happening".