Differential Effect of Early or Late Implementation of Prior Authorization Policies on the Use of Cox II Inhibitors

Abstract

State Medicaid programs introduce many types of prescribing restrictions to manage pharmaceutical use and expenditure. Little is known about the differential effect of implementing prior authorization (PA) policies at market entry versus waiting until several years later when prescribing behavior may already be established. We sought to examine the impact on overall use of Cox II inhibitors of PA policies implemented at market entry versus at least 2 years after market entry. We quantified Cox II inhibitor and nonselective nonsteroidal anti-inflammatory drug (NSAID) utilization for state Medicaid programs from January 1996 to September 2003. We used generalized estimating equations, Tukey's studentized range test and segmented linear regression on state Medicaid programs to determine the significance of changes in medication use. The primary end point was the number of defined daily doses (DDD) per 1000 population per day. Six states implementing prescribing restrictions for Cox II inhibitors at market entry had the lowest rates of uptake, averaging 10.9 DDD/1000/d. Twelve states adopting restrictions more than 2 years after market entry experienced declines in use from 23.0 DDD/1000/d before to 13.9 DDD/1000/d after the restrictions (P < 0.01). The 17 states that had never restricted access had the highest utilization, averaging 29.0 DDD/1000/d. Implementing prescribing restrictions at market entry of Cox II inhibitors was effective in restricting uptake. Despite the difficulty in changing well-established prescribing patterns, utilization in states implementing policies 2 years after market entry approached that of the early adopting states within 1 year. Clinical outcomes of such policies remain unknown.