Mixed Results from Tightening Formulary Restrictions
Tighter restrictions led to discontinuation, adherence, generic use, and cost reduction.
Previous research has shown that formulary restrictions can reduce utilization and spending for targeted drugs.
A new study published in the Journal of Clinical Pharmacy and Therapeutics examined how transitioning from a standard restricted formulary to an even more restrictive one impacted (1) therapy disruption, (2) medication adherence, (3) pharmacy costs, and (4) use of generics among a patient population with common chronic conditions.
Researchers conducted a retrospective cohort study, drawing data from the CVS Health system from 2013 to 2014. They identified 2 study cohorts: “continuers” were continuously enrolled in a standard formulary (SF) that transitioned into a more restrictive Value Formulary (VF) in January 2014; and “initiators” began a new prescription fill under the new VF guidelines.
Each VF intervention group was matched to an equivalent control group of patients covered by a standard formulary using propensity scores based on demographic, socioeconomic, and baseline drug utilization characteristics.
Continuers were evaluated for changes in therapy disruption following implementation of the more restrictive VF using the chi-square test. Changes in continuers’ pharmacy costs and generic dispensing rate (GDR) were measured per utilizer per month (PUPM) and analyzed through segmented regression of interrupted time series data with generalized estimating equations.
Initiators were evaluated for medication adherence using the measure monthly proportion of days covered (PDC). Differences in monthly PDC between intervention and control groups were determined using multivariate linear regression.
The total study sample was quite large. The matched cohort of continuers included 127,894 patients, 63,947 in each intervention/control group. The matched cohort of initiators included 54,386 patients, with 27,193 patients in each intervention/control group.
Findings on More Restrictive Formularies
The transition to VF affected medication coverage for about 13% of the intervention group of continuers. This includes all patients whose medication was either no longer covered, or covered more restrictively under VF. Proportions of affected patients ranged from 3.1% with depression to 27.5% with diabetes.
Continuers experienced a 1.3% (P<.001) increased rate of therapy discontinuation compared with patients who remained in a standard formulary. There was no increase in therapy disruption for hypertension, whereas hyperlipidemia therapy exhibited the highest rate of discontinuation (3%; P<.001). The VF population also switched drugs at a 4.4% (P<.001) higher rate.
For continuers who transitioned from SF to VF, costs decreased by $19.30 PUPM (P<.001) consistently across all chronic conditions, with the most cost savings for diabetes and the least savings for depression.
For the same group, GDR increased by 4.2% (P<.001) consistently across all chronic conditions, with the highest increase for diabetes and the lowest increase for depression.
In the initiator cohort, monthly medication adherence rates were 1.5% (P<.001) higher for VF versus SF groups. Statistically significant adherence improvement was measured for VF patients initiating therapy for hypertension, diabetes, and depression, but not for hyperlipidemia.
Formulary Restrictions and Therapy Discontinuation
Investigators said their study results suggest that strategically tightening restrictions on formularies may lead to a modest one-time increase in therapy discontinuation, offset by improvements in adherence of a similar magnitude. Their results also showed that a more restrictive formulary led to significant cost savings and increased generic use.
The implications of these findings should be considered in context, said the authors. This study was accompanied by an aggressive patient education and support campaign. The more restrictive VF formulary boasted an evidence-based design and a comprehensive selection of essential drug options, including generics, in all drug classes. Finally, continuers in this study were already acclimated to a modestly restrictive formulary, possibly conditioning them to make an easier transition.