Retrospective evaluation of the impact of copayment increases for specialty medications on adherence and persistence in an integrated health maintenance organization system.

BACKGROUND

Specialty drugs are generally defined as high-cost injectable, infused, oral, or inhaled drugs that require close monitoring. Specialty drugs account for an increasing percentage of total drug expenditures, and management of specialty drugs has become a priority. A Central Texas-based integrated health maintenance organization system implemented a specialty drug benefit to manage expensive specialty drug costs.

OBJECTIVES

Our objective was to measure and compare the change in adherence and persistence after implementation of copayment increases for select specialty medications used on a long-term basis (at least 2 years).

METHODS

Patients who were long-term users of anti-inflammatory, immunosuppressant, cancer, and multiple sclerosis medications were selected. The intervention group consisted of those whose out-of-pocket payment for specialty medications increased, and the control group consisted of those whose out-of-pocket costs did not change. Adherence, defined by proportion of days covered, was measured every 3 months for 12 months before and after the change. Individual growth model analysis evaluated the changes in adherence. Cox regression analysis determined the difference in persistence between groups.

RESULTS

There were 178 and 202 patients in the intervention and control groups, respectively. The growth model showed a small but statistically significant decrease in proportion of days covered of 0.040 after copay changes in the intervention versus control group (P < 0.001) for immunosuppressants. The Cox regression analysis indicated a higher probability of intervention patients on anti-inflammatory drugs (hazard ratio [HR] = 2.53; 95% CI, 1.38-4.62) and immunosuppressants (HR = 3.01; 95% CI, 1.20-7.56) would be nonpersistent compared with those in their control groups.

CONCLUSIONS

The move to the specialty formulary allows for closer scrutiny of specialty utilization by pharmacists, who actively monitor utilization and access. Despite the minimal adherence decrease and significant persistence changes with certain drug types, the results indicated relatively more stability with specialty drug use than reported with traditional pharmaceuticals.