Escitalopram co-prescription in anastrozole-treated breast cancer patients

Abstract

Objective: The purpose of the study was to evaluate the impact of escitalopram co-prescription on plasma anastrozole levels in post-menopausal breast cancer patients.

Methods: A total of 24 post-menopausal operated breast cancer patients co-prescribed with escitalopram and anastrozole were included. Blood samples were collected, before and 1-month after the onset of escitalopram to analyze plasma anastrozole and estradiol levels.

Results: No significant difference was noted in basal plasma anastrozole levels with respect to age, body mass index (BMI), tumor stage, previous antineoplastic treatments, concomitant medications, and serum estradiol levels. Overall, 17 patients completed the 1-month escitalopram treatment, while 7 patients discontinued escitalopram within the 1^st week of the treatment. Basal anastrozole levels of 24 patients were 26.1±2.4 ng/mL. Among 17 patients who continued 1-month escitalopram treatment was associated with significant increase in plasma anastrozole levels (24.5±2.3 ng/mL to 32.2±3.2 ng/mL, p<0.05). Notably, 1-month escitalopram use was associated with significant increase in plasma anastrozole levels only in the subgroup of obese (BMI >29 kg/m²) patients (23.1±2.8 to 35.9±4.7 ng/mL, p<0.01), while no such interaction was noted among non-obese patients. The estradiol levels of the patients were below ≤10 pg/mL in 75% of patients and no change occurred after escitalopram administration.

Conclusion: Escitalopram co-prescription resulted in significant increase in plasma anastrozole levels without affecting the serum estradiol levels. Our findings emphasize the need for close monitoring in case of concomitant use of anastrozole and escitalopram, especially in obese patients and the potential role of therapeutic drug monitoring.

Keywords: Anastrozole; breast cancer; escitalopram; obesity; therapeutic drug monitoring.

Figure 1

A representative chromatogram of elution of external standard injection into the HPLC system where tolterodine was used as an internal standard (A), the regression analysis yielded an r² of 0.9930 (B).

Figure 2

(A) Basal plasma anastrozole levels in discontinuers (n=7) vs. continuers (n=17) of 1-month escitalopram treatment; (B) anastrozole levels before (^1st measurement) and after (2^nd measurement) escitalopram treatment among continuers (n=17), *P<0.05; paired t-test.

Figure 3

Plasma anastrozole levels compared to before (1^st measurement) and after (2^nd measurement) escitalopram treatment among continuers with BMI >29.9 kg/m² (n=10) and among continuers with BMI ≤29.9 kg/m² (n=7), **P<0.01; Paired t-test.