Determinants of Poor Adherence
In a real-world setting, patients stop their treatment for a number of reasons, including inconvenient and complicated dosing requirements as well as drug-related side effects.
Although bisphosphonates are the most potent currently approved antiresorptive agents, such treatments pose a particular challenge, since these medications require more effort than simply swallowing a pill. Current bisphosphonates need to be administered according to strict treatment guidelines in order to achieve optimum absorption and minimize the risk of adverse gastrointestinal events. These include the need to remain in an upright position for at least 30 min following administration and before eating breakfast and to swallow the medication with water only. Studies of self-reported drug-taking behavior have shown that even when complete instructions are given, between 25 and 50% of patients disregard at least one requirement.[79,80] These strict treatment guidelines can contribute to poor adherence but also decrease the efficacy of treatment if they are not adequately respected. Minimization of disruption to lifestyle associated with more-frequent oral dosing and the need for fasting appear to be important factors in patient choice, as described by Richards et al.. Drug-related adverse events are a common reason for the discontinuation of bisphosphonate treatment. One large study surveying prescription users at a large national pharmacy chain found that the most-commonly cited cause of discontinuing weekly or monthly bisphosphonate therapy was the occurrence of troublesome side effects (67%). In a community-based cohort from the Prospective Observational Scientific Study Investigating Bone Loss Experience (POSSIBLE US), occurrence of gastrointestinal side effects significantly increased the likelihood of therapy discontinuation. Moreover, it was demonstrated that gastrointestinal side effects were a risk factor for discontinuation even among patients who had been stable on therapy for 6 months or longer.
The asymptomatic nature of osteoporosis may also affect adherence to a medication regimen. Since the condition manifests itself episodically through traumatic events, such as fall-related fractures, patients may not perceive the daily risks of these events that are related to bone loss. This difficulty is compounded further by the fact that, in an asymptomatic condition, the benefits of treatment are not immediately apparent and, consequently, patients do not consider themselves in need of medication. Moreover, patients may feel that the treatment benefit does not outweigh the perceived risk of adverse effects from treatment.
Another important factor influencing adherence is the cost of medication. Kennedy et al. used data from 14,464 community-dwelling Medicare beneficiaries to study possible patterns in unfilled Medicare prescriptions. They were asked if there were any prescriptions that had not been collected that were written out or phoned in by a physician. Respondents were asked to answer questions about medications in general as they were not asked the names or types of specific medications. In 2004, an estimated 1.6 million Medicare beneficiaries, or 4.4%, admitted failing to collect or refill at least one prescription. The most-common reasons for not collecting these prescriptions were cost (55.5%) and lack of insurance coverage (20.2%). Weiss et al. examined data derived from a large community prescription database over a 1-year period and showed that patients with higher out-of-pocket expenditures were less likely to persist with treatment (patients with expenditures ≥US$75.00 had 13–34% poorer persistence than patients paying $16–$20).
Other potential barriers to treatment are older age, patients' beliefs in the effectiveness and safety of treatment, poor knowledge regarding risk factors and osteoporosis, inadequate follow-up by healthcare providers, fears about addiction to or dependence on treatment, an increasing number of comorbid conditions and use of multiple medications.[86–90]
Expert Rev Pharmacoeconomics Outcomes Res. 2010;10(6):677-689. © 2010 Expert Reviews Ltd.
Cite this: Overcoming Problems with Adherence to Osteoporosis Medication - Medscape - Dec 01, 2010.