Formulary restriction of selective serotonin reuptake inhibitors for depression: potential pitfalls

The American healthcare market is currently estimated at more than 900 billion US dollars with double digit rising costs per year. Psychotropic agent costs have more than kept pace with market increases. Medication acquisition costs are an obvious focus for limiting costs in various care systems. Restrictive formularies are a common method of attempting to limit costs. To support our opinion that a single agent is ill advised, we explored the available evidence on the intended and unintended consequences of having a single or exclusive selective serotonin reuptake inhibitor (SSRI) on a formulary. Central to this position is an assumption of the interchangeability of SSRIs; we examined the evidence for and against this through a model to determine the probability of interchangeability. We conclude that the practice of having a single SSRI on the formulary for a healthcare plan seems ill founded. Patients who switch antidepressants remain in treatment 50% longer and cost approximately 50% more to treat in a more costly treatment setting. Giving the primary care physician several antidepressant choices can provide more options to continue treatment of his or her patient in the less expensive primary care setting. In terms of cost containment, formulary restrictions are far more likely to have the opposite effect.