Volume 2 · Nº 4 Supl · October 2010
Osteoporosis is a common disease, responsible in great part for the fractures which occur in people over 50 years of age. Due to diverse pathogenic mechanisms a reduction in bone mass is produced, which is accompanied by an increase in bone fragility. Osteoporotic fractures are a health problem of great magnitude due to their repercussions not only in the health and quality of life of the patient, but also for the economic and social costs which its treatments and their side effects brings.read more
Nowadays we have available a highly varied therapeutic arsenal for the treatment of osteoporosis1. The biphosphonates constitute the group of drugs most commonly used for the treatment of this disease and are the first choice according to the SEIOMM guides2. Among the biphosphonates, zoledronic acid is the most potent third generation nitrogenated biphosphonate currently on the market3,4. Its action mechanism means that it has a great affinity with the hydroxyapatite crystals of bone, above all in those areas of high bone turnover, reducing the speed of bone remodelling. In turn it is released during bone resorption and internalised by the osteoclasts, which interfere in the metabolism and function of these cells, and favour their apoptosis5. Zoledronic acid has an affinity for bonding with hydroxyapatite higher than other biphosphonates6 and is the most powerful inhibitor of farnesyl-diphosphate-synthase and of bone resorption7.
Zoledronic acid is the first drug which allows annual treatment in postmenopausal patients affected by osteoporosis, or at high risk of fracture. The administration of 5 mg of zoledronic acid once a year has been shown to be efficacious in the reduction in risk of vertebral fractures in patients with postmenopausal osteoporosis or hip fracture due to a recent light trauma8. In turn it produces an increase in bone mineral density and a reduction in markers for bone turnover9. Being generally well tolerated, its annual administration makes it a comfortable and efficacious treatment option, in such a way that the patient’s adherence to treatment is not a problem, thus maintaining the protection of bone over a whole year.
The osteoporotic fracture has an enormous economic impact, in addition to its effects on health. In the year 2000, it was estimated that there were 4 million new fractures in Europe – some 8 fractures per minute, or one fracture every 8 seconds1. Of these, 0.89 million were hip fractures. The direct costs have been estimated at nearly 32 billion euros, which it is expected will increase to 77 billion euros by 2050 as a function of demographic changes expected in Europe2.
The combined risk of suffering hip, forearm and clinical vertebral fractures is approximately 40%, similar to that of developing cardiovascular disease3. In Caucasian women, the risk of hip fracture over their lifetime is 1/6, higher than that of suffering breast cancer -1/9-4.
In our country it is calculated that 2 million women have osteoporosis, putting its prevalence at 26.1% of women over 50 years of age5. More than 25,000 fractures appear annually, from which originate direct costs of more than 126 million euros, with indirect costs reaching 420 million euros annually6.
The importance of osteoporosis lies in the fact that it predisposes the appearance of fractures, which means that it constitutes a major health problem1,2. The fractures most commonly associated with osteoporosis are vertebral, hip and the distal radius, or Colles, fractures3. It has been estimated that the risk of a patient with osteoporosis of suffering any fracture during the rest of their life varies between 40-50% in women and between 13% and 22% in men, and, in the specific case of hip fracture, the risk for a white woman is 17.5%, while for a man it is 6% 1,2,4.
All these fractures have a high level of morbidity and result in a high social-health cost4,5: for example, approximately 25% of vertebral fractures and practically all fractures of the hip require hospitalisation2. But, in addition, osteoporotic fractures, especially of the hip, have a considerable mortality. Indeed, studies carried out in this country show that at the end of one year after a hip fracture approximately 30% of patients have died, increasing to 40% when the follow up is extended to two years6-10. Other studies have described a reduction in survival at 5 years of 15% after a hip fracture, observing that the greater part of the deaths occur in the first six months after it2.
Osteoporosis is a chronic process, usually asymptomatic, which deteriorates the bone, making it susceptible to fracture. The ultimate objective in the treatment of osteoporosis is to minimise the risk of suffering new fractures11-14. There is no drug which reduces this risk to zero: most of the drugs available nowadays for the treatment of osteoporosis obtain reductions of between 40% and 65%11-14, even when the medication is taken continuously during a period of time which varies between 3 and 5 years. These circumstances (lack of symptoms, necessity for prolonged treatment) means that, as happens with other similar diseases (arterial hypertension, hypercholesterolemia, diabetes mellitus), the abandonment by the patient of their medication is common, and for many diverse reasons. Institutions such as the World Health Organisation and the American Heart Association recognise that one of the main problems in the treatment of chronic diseases in developed countries is non-compliance on the part of patients in the correct taking of their medicines15,16.
With reference specifically to osteoporosis, multiple studies have demonstrated deficiencies in adherence to treatment by patients, and this has been studied with all drugs used: calcitonin, oestrogen therapy, raloxifen, teriparatide and biphosphonates17-22, and some have even compared the abandonment of osteoporosis treatment depending on which drug is being used. The existing works are highly varied, and often have contradictory results23-28. The disparity in the populations studied and the methodologies applied explain the difficulties in comparing results. However, all these studies agree on the fact that adherence to osteoporosis treatment is, in general, low, and that in the first year the percentage abandonment is found to be between 30% and 50% in most cases.