Impact of Medicaid prescription copayments on use of antipsychotics and other medications in patients with schizophrenia.

OBJECTIVE

To assess the impact of Medicaid prescription copayment policies on anti-psychotic and other medication use among patients with schizophrenia.

METHOD

The study sample included fee-for-service adult Medicaid patients with schizophrenia. Medicaid claims records from 2003-2005 from 42 states and D.C. were linked with county-level data from the Area Resource File and findings from a state Medicaid policy survey. Patient-level fixed-effects regression models examined the impact of increases in generic copayments and generic/brand copayment differentials on monthly use of anti-psychotic (overall and by generic/brand status) and other non-antipsychotic medications. Medications for hypertension, hyperlipidemia, and diabetes in sub-groups of patients with these comorbidities were also examined.

RESULTS

Prescription copayment changes had a statistically significant but small impact on anti-psychotic use. For instance, for every $1 increase in the minimum or generic copayment per prescription, there was a reduction of 1.4 anti-psychotic drug fills per 100 patient months (relative reduction = 1.9%). The generic/brand copayment differential increases also had a minimal impact in changing utilization of first-generation (generic) and second-generation (brand) anti-psychotics. Effects of copayment changes on non-anti-psychotic medication use were substantially higher; for each $1 generic copayment increase, there was a reduction of 23 non-anti-psychotic drug fills per 100 patient months (relative reduction = 10.1%). Similarly, for each $1 increase in the generic/brand copayment differential, there was a reduction of 15 non-anti-psychotic drug fills (relative reduction = 5.6%). Reductions in the number of prescriptions filled for antidiabetics, antihypertensives, and lipid-lowering agents were 4-11-fold higher than corresponding reductions for anti-psychotics.

LIMITATIONS

Because federal law requires pharmacists to fill medications for Medicaid patients regardless of the ability to pay, these results may under-estimate the true impact of copayment increases.

CONCLUSIONS

Medicaid prescription copayment increases resulted in only a minimal decline in anti-psychotic medication use, but much larger reductions in use of other medications, particularly cardiometabolic medications.