A Comparison of Pharmacy Dispensing Channel Use and Adherence to Specialty Drugs Among Medicare Part D Beneficiaries

BACKGROUND: Nonadherence to specialty drugs has been associated with poor clinical and economic outcomes. Studies conducted using commercial health plans suggest that patients who use specialty pharmacies have higher adherence compared with patients using retail pharmacies. However, little is known about the frequency of dispensing channel use or the association of dispensing channel use with adherence to specialty drugs among Medicare Part D beneficiaries. OBJECTIVES: To (a) describe the use of pharmacy dispensing channels by patients using self-administered specialty drugs in Medicare Part D and (b) study the association between dispensing channel use and adherence to specialty drugs in this population. METHODS: This study analyzed 2010 Medicare Part D data. Specialty drugs were defined as drugs with a mean cost ≥ $600 per month. We identified the top 13 specialty medications by cost and classified patients into the following classes: anticancer, disease-modifying therapy (DMT), and tumor necrosis factor inhibitor (TNFi). Dispensing channels included retail, specialty, mail order, long-term care, and other. We included patients continuously enrolled in Medicare Part D who had ≥ 1 prescription for a specialty medication before the end of June 2010. These patients were followed until the end of 2010. Patients with proportion of days covered (PDC) ≥ 0.8 were considered adherent. Adherence rates were calculated by weighting for therapeutic class after weighting for drug mix. Multivariable logistic regression analysis examined the association between dispensing channel and adherence. RESULTS: Of 5,430 patients, 1,248 were dispensed anticancer medications, 1,723 were dispensed DMTs, and 2,459 were dispensed TNFi drugs. About 16% used specialty, 74% used retail, 4% used mail order, 4% used long-term care, and 3% used other channels. The distribution pattern was similar when stratified by therapeutic class. In the descriptive analysis, patients using the specialty channel for the anticancer and TNFi classes had 7% and 10% higher adherence rates, respectively, compared with retail. For the DMT class, the adherence rate was higher for mail order but similar for retail and specialty channels. Adjusted analysis found that overall, specialty users had 23% higher odds for being adherent compared with retail users (P = 0.0104). For the anticancer and TNFi classes, specialty users had 39% (P = 0.0311) and 55% (P = 0.0005) higher odds, respectively, for being adherent than retail users. For the DMT class, no significant association was observed between dispensing channel and adherence (P = 0.9691). CONCLUSIONS: Nearly three quarters of Medicare patients on specialty therapies included in this study used the retail channel compared with one sixth who used the specialty channel. Overall, specialty channel use was associated with higher adherence compared with retail channel use. However, this relationship varied by therapeutic class. The specialty channel was associated with higher adherence among patients from the anticancer and TNFi classes but not among the DMT class.