Direct cost of depression: analysis of treatment costs of paroxetine versus Imipramine in Canada.

OBJECTIVE To assess the potential economic impact of new and more expensive antidepressants on the overall cost of treatment using cost-effectiveness analysis. METHOD For this analysis, a computerized decision tree of clinical practice was developed to model the 12-month treatment of moderate to severe depression in Canada. To complete the model, data were obtained from physician panels, the Ontario Ministry of Health, and clinical comparative trials of paroxetine, a selective serotonin reuptake inhibitor, and imipramine, a tricyclic antidepressant. RESULTS The overall cost of treatment when paroxetine 30 mg per day was used first-line was found to be lower than when generic imipramine was used as the initial therapy ($1697 versus $1793). The higher drug cost of paroxetine ($1.69 per day) versus imipramine ($0.05 per day) was offset by a higher rate of treatment failures with the tricyclic necessitating an alternate therapy, additional physician visits and/or hospitalization. Sensitivity analysis of key variables determined that drug price and relapse rates after discontinuation were relatively insensitive predictors of the overall cost of care. More important was the continuation rate while on different therapies. CONCLUSION Paroxetine demonstrated a cost-benefit relative to imipramine when the continuation rate was > or = 47%. Clinical trials of paroxetine have reported continuation rates of 41% to 65%, suggesting that paroxetine is a cost-effective alternative to imipramine in the 1-year management of patients with moderate to severe depression.