The Impact of Open Access to Atypical Antipsychotics on Treatment Costs for Medi-Cal Patients with Bipolar Disorder

Background: The California Medicaid Program (Medi-Cal) provided open access to atypical antipsychotics in October 1997. This study investigated the impact of open access to atypical antipsychotics on the costs and duration of therapy for patients with bipolar disorders. Methods: Paid claims data from Medi-Cal were used to identify episodes of treatment using antipsychotics, antidepressants, mood stabilizers, or selected anticonvulsants initiated by patients with bipolar disorders. Episodes of treatment were assigned to one of three time periods based on the start date: closed access (July 1994 to September 1997); a transition period (October 1997 to March 1998); and open access (April 1998 to August 1999). Ordinary least squares models for the cost and duration of drug therapy were estimated for episodes of treatment started after a break in all bipolar-related drug therapy (restarts) and switching/augmentation episodes. Results: 123_796 restart and 206_157 switching/augmentation episodes were identified. Patients with bipolar disorders cost between $US8000 and $US9000 annually (year of values 1998). Open access increased total costs by $US165-203 per year for restart episodes and $US75-125 per year for switching/augmentation episodes, primarily due to increased drug costs of $US101-103 for restart episodes (p_<_0.001) and $US124 for switching/augmentation episodes (p_<_0.001). Days of therapy decreased by 3.67 days for restart episodes (p_<_0.001) and increased by 2.59-2.62 days for switching/augmentation episodes (p_<_0.001) from the closed access period to the open access period. Conclusions: Conventional antipsychotic medications are not used for long-term drug therapy for bipolar disorders, and the long-term effectiveness of atypical antipsychotics was not well established in October 1997. It is not surprising that open access to atypical antipsychotics had only limited effects on the costs and duration of therapy for these patients.