The economics of selective serotonin reuptake inhibitors in depression - Acritical review

The prevalence of depression and the high costs associated with its treatme nt have increased interest in pharmacoeconomic evaluations of drug treatmen t, particularly in the 1990s as the use of selective serotonin (5-hydroxytr yptamine; 5-HT) reuptake inhibitors (SSRIs) expanded substantially. This re view presents results from specific studies representing the key study desi gns used to address the pharmacoeconomics of SSRI use: retrospective admini strative database analyses, clinical decision analysis models, and randomis ed clinical trials. Methodological considerations in interpreting results a re highlighted. In retrospective administrative database analyses, most comparisons have be en made between SSRIs and tricyclic antidepressants (TCAs). A few studies h ave addressed differences between SSRIs. The studies focused on healthcare cost (to payer) and cost-related outcomes (e.g. treatment duration, drug sw itching). Although SSRls are generally associated with higher drug acquisit ion costs than are TCAs, total healthcare costs are at least offset, if not decreased, by reductions in costs associated with use of SSRIs. Although s tudies from the early 1990s show some advantage for fluoxetine, the results are limited by use of data from shortly after the introduction of paroxeti ne and sertraline; studies from the mid-1990s on that compare drugs within the SSRI class show general equivalence in terms of cost. Important methodo logical advances are occurring in retrospective studies, with selection bia s and other design limitations being addressed statistically. Clinical decision analysis models permit flexibility in terms of ability to specify different alternative treatment scenarios and varying durations. S ensitivity analysis aids interpretability, although model inputs are limite d by data availability. Results from short term (1 year duration or less) s tudies comparing SSRIs and TCAs suggest that SSRIs are more cost effective or that there is no difference. Longer term studies (lifetime Markov models ) focus more on the impact of maintenance antidepressant therapy and show m ore mixed results, generally favouring SSRIs over TCAs. The results indicat e that the effect of SSRIs is mainly through prevention of relapse. Importa nt assumptions of these models include fewer serious adverse effects and lo wer treatment discontinuation rates with SSRIs. Naturalistic clinical trials provide greater generalisability than traditio nal randomised clinical trials. One naturalistic trial found that nearly ha lf of TCA-treated patients switched to another antidepressant within 6 mont hs; only 20% of SSRI-treated patients switched. Cost differences between gr oups were minimal. These studies indicate few differences in medical costs, depression outcomes and health-related quality of life between TCAs and fl uoxetine, although fewer fluoxetine-treated patients switched treatment.