Determinants of adherence to osteoporosis treatment in clinical practice.

INTRODUCTION: Poor adherence to prescribed treatments is widespread in clinical practice and this can lead to potentially life-threatening events. This problem is apparently very common for osteoporosis treatment but the causes of discontinuation and low compliance are complex and poorly defined.
METHODS: Global adherence to osteoporosis treatment was specifically addressed in a nation-wide survey carried out in 9851 postmenopausal women referred to 141 Italian centres for osteoporosis management for a follow-up assessment, at least one year after having been prescribed a treatment with one of the following drugs: calcium+/-vitamin D supplements alone (CaVitD), hormone replacement therapy (HRT), raloxifene 60 mg (RLX), intramuscular clodronate 100 mg/7-14 days (CLOD), risedronate 5 mg/day (RIS) and alendronate 10mg/daily (ALN10) or 70 mg once weekly (ALN OW).
RESULTS: Overall 19.1% of the patients discontinued the prescribed drug before attending the bone mass re-evaluations, more than half of them within the first 6 months. The discontinuation rate was significantly different between the treatments. The medications most frequently interrupted within one year were CLOD (28.7%; p<0.01 versus any other treatment), while by far the least interrupted was ALN-OW (6.9%; p<0.001 versus any other treatment). The most frequent reasons for discontinuation were drug related side effects, insufficient motivation to treatment and fear of side effects. The prevalence of the reasons for discontinuation were different among treatments: safety concerns were very common for HRT, lack of motivation was the most common cause for CaVitD and CLOD, and drug related side effects for RIS, ALN and RLX. Persistence to treatment was significantly higher in patients with previous vertebral fractures, densitometric osteoporosis, on corticosteroid or anti-inflammatory treatments. A significantly increased risk of treatment interruption was found among patients on benzodiazepine or gastro-protective agents and in patients in whom a bone measurement was not readily available. The highest compliance to recommended dosing was observed with ALN OW and HRT (p<0.001 versus any other) and the lowest for CaVitD (p<0.01 versus any other). Poor treatment compliance (<50% drug taken) was significantly related to benzodiazepine and gastroprotective use, while a significantly better compliance was associated with recognized risk factors for osteoporosis: early menopause, low bone mass values values, previous vertebral fractures. The poorest adherence was observed when treatments were prescribed by General practitioners (GPs), and orthopaedic surgeons (p<0.01 versus global mean).
CONCLUSIONS: The results of this large survey of Italian osteoporotic women indicates that the most important determinant of both persistence and compliance to treatment is the type of drug prescribed with a definite advantage of ALN-OW. Treatment compliance is particularly poor for CaVitD and this emphasizes the need for new ways to supplement at least vitamin D. The main reasons for discontinuation are side effects and lack of motivation while the best treatment adherence was observed in patients with severe and well documented osteoporosis.