One in 3 Patients Fail to Fill Initial Prescriptions‏

Laurie Barclay, MD

March 31, 2014

Nearly one third of all initial drug prescriptions were not filled within 9 months, with nonadherence highest for expensive drugs and chronic preventive therapies, according to a primary care network cohort study published in the 1 April issue of Annals of Internal Medicine.

"Many chronic conditions can be successfully managed with pharmaceutical interventions, but 2 common treatment barriers hinder optimal disease management," write Robyn Tamblyn, PhD, from McGill University, Montreal, Quebec, Canada, and colleagues. "First, there is a high prevalence of nonadherence with long-term therapy, a problem that is associated with an increase in emergency department (ED) visits and health care costs. Second, there is an underuse of preventive therapies, such as inhaled steroids for preventing asthma exacerbations, which has been attributed to health professionals' failure to follow evidence-based guidelines."

The goals of this study were to estimate the incidence of primary nonadherence in primary care and to identify drug-related, patient-related, and physician-related characteristics associated with nonadherence.

The prospective cohort for this study consisted of 15,961 patients in a primary care network of 131 physicians in Quebec. The researchers linked incident prescriptions from primary care electronic health records between 2006 and 2009 to provincial drug insurer data on all drugs dispensed from community-based pharmacies.

The investigators defined primary nonadherence as not filling an incident prescription within 9 months. Using multivariate alternating logistic regression, they estimated predictors of nonadherence and accounted for patient and physician clustering.

Of 37,506 incident prescriptions written for the 15,961 patients, nearly one third (31.3%) were not filled. This rate was greater for new users (34.3%) than for those who were switching treatment from 1 drug to another within the same pharmacologic class (11.6%).

Drug and Patient Factors Affect Nonadherence

Patients were most likely to fill antibiotic prescriptions. Drug predictors of nonadherence were those in the upper quartile of cost (odds ratio [OR], 1.11 [95% confidence interval (CI), 1.07 - 1.17] compared with antimicrobials), as well as skin agents, gastrointestinal drugs, and autonomic drugs used as chronic preventive therapies for ischemic heart disease, depression, and other conditions.

Factors associated with lower odds of nonadherence were increasing patient age (OR per 10 years, 0.89; 95% CI, 0.85 - 0.92), eliminating prescription copayments for low-income groups (OR, 0.37; 95% CI, 0.32 - 0.41), and a greater proportion of all physician visits with the prescribing physician (OR per 0.5 increase, 0.77; 95% CI, 0.70 - 0.85).

Factors associated with greater risk for nonadherence were higher copayments, recent hospitalization, and more severe comorbid conditions.

"Failure to fill an initial prescription is common and requires more study for improvement," the study authors write. "Lower prescription copayments and a greater proportion of all care visits being with the prescribing physician were among factors associated with filling the prescription."

Study limitations were inability to assess patient rationale for not filling their prescriptions and other clinical variables that may affect filling and/or using prescriptions.

"Future research should estimate the contribution of medication attitudes and beliefs to the likelihood of primary nonadherence as well as the effect of nonadherence on subsequent illness, death, and health care use," the study authors conclude.

The Canadian Institutes of Health funded this study. The authors have disclosed no relevant financial relationships.

Ann Intern Med. 2014;160:441-450.

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