Duke 2008 | ASHE | Equity and Efficiency in Health and Healthcare

Pharmaceutical industry critics assert that, rather than developing breakthrough drugs, manufacturers focus too much effort on developing drugs that are only marginally different from medications already on the market, including reformulations of existing products. Reformulations of psychiatric medications often involve less frequent (e.g. once versus three times daily) or easier-to-administer dosing than the originator products. Under the Hatch-Waxman Act of 1984, manufacturers can obtain three years of additional market exclusivity for the introduction of a new product formulation, so manufacturers have an incentive to try to shift demand for the original formulation of a brand drug that will soon lose patent protection onto a reformulation of that drug in order to extend market exclusivity for their products. Special formulations intended to improve patient adherence may be particularly useful for some patients with mental illness, for whom the illness itself may affect the patient's ability to adhere to a medication regimen. However, the marginal benefit of a reformulation relative to other therapeutic alternatives is likely to vary across patients, and thus the extent to which the marginal benefits of a reformulation exceeds its marginal costs (relative to a less-expensive generic medication, for example) is unclear.

We explore early adoption of six new psychiatric medication formulations (Effexor XR, Lexapro, Paxil CR, Remeron Soltab, Wellbutrin SR, and Wellbutrin XL) among beneficiaries in a large state Medicaid program. We examine adoption rates in the year after introduction of each new formulation among "incident users" of antidepressants and among individuals who were currently using an antidepressant at the time of the reformulation's introduction ("current users"). We estimate drug-specific logistic regression models of the probability of filling a prescription for a particular reformulation, controlling for patient demographic characteristics, mental health diagnosis, Medicaid eligibility status, institutional status, provider specialty, and county-level prescribing trends. Preliminary analyses suggest that utilization rates for reformulated products were significantly different across different racial and ethnic groups. Male antidepressant users were more likely to receive a reformulation than female antidepressant users. Medicaid beneficiaries using the original formulation of the molecule (either the originator brand or a generic equivalent, if available) at the time the reformulation was introduced were significantly less likely to use the reformulation compared to individuals using a different antidepressant before introduction of the reformulation. Current antidepressant users who had no mental health diagnoses in the six months before the reformulation was introduced were significantly less likely to use the reformulation than antidepressant users who had received a mental health diagnosis in the pre-introduction period. Individuals using skilled nursing facility care in the six months before reformulation introduction were typically more likely to use reformulations that involved less frequent dosing (e.g., Wellbutrin SR, Wellbutrin XL) or possibly quicker onset of action (e.g., Paxil CR) but less likely to use other types of reformulations (e.g., Lexapro, Remeron Soltab). This study will provide information on patient and provider characteristics that influence use of psychiatric medication reformulations and shed some light on the social value of these medications.