Economic consequence of switching to citalopram after its generic entry for adult patients with major depressive disorder (MDD) treated with escitalopram

Objective

To estimate, from a third-party payer's perspective, the effects of switching from escitalopram to citalopram, after the generic entry of citalopram, on hospitalization and healthcare costs among adult MDD patients who were on escitalopram therapy.

Methods

Adult MDD patients treated with escitalopram were identified from Ingenix Impact claims database. MDD- and mental health (MH)-related hospitalization rates and healthcare costs were compared between 'switchers' (patients who switched to citalopram after its generic entry) and 'non-switchers'. MDD- and MH-related outcomes were defined as having a primary or a secondary diagnosis of ICD-9-CM = 296.2x, 296.3x and ICD-9-CM = 290-319, respectively. A propensity score matching method that estimated the likelihood of switching using baseline characteristics was used. Outcomes were examined for both 3-month and 6-month post-index periods.

Results

The sample included 3,427 matched pairs with balanced baseline characteristics. Switchers were more likely to incur an MDD-related (odds ratio [OR] = 1.52) and MH-related hospitalization (OR = 1.34) during the 6-month post-index period (both p < 0.05). Compared to switchers, non-switchers had significantly lower MDD- and MH-related hospitalization costs ($248.3 and $219.8 lower, respectively) and medical costs ($277.4 and $246.4 lower, respectively) (all p < 0.05). Although non-switchers had significantly higher MDD- and MH-related prescription drug costs, overall they had significantly lower total MDD- and MH-related healthcare costs ($109.9 and $93.6 lower, respectively; both p < 0.001). The 3-month results were consistent with these 6-month findings.

Limitations

The study limitations included limited generalizability of study findings, inability to differentiate switching from escitalopram to citalopram due to medical reasons versus non-medical reasons, and exclusion of indirect costs from cost calculations.

Conclusions

Compared to patients maintaining on escitalopram, switchers from escitalopram to citalopram experienced higher risk of MDD- and MH-related hospitalization and incurred higher total MDD- and MH-related healthcare costs. The economic consequences of therapeutic substitution should take into account total healthcare costs, not just drug acquisition costs.