Key result
Concomitant use of tamoxifen and serotonin reuptake inhibitors in breast cancer patients significantly prolonged the mean QTc-interval by 12.4 ms compared to tamoxifen monotherapy.
Why the study?
Concomitant use of serotonin reuptake inhibitors with tamoxifen may cause additional QTc-interval prolongation and increased cardiac risk, but this potential drug-drug interaction required investigation.
Does concomitant use of serotonin reuptake inhibitors prolong the QTc-interval in breast cancer patients treated with tamoxifen?
Observational (n=100)
Yes
Does concomitant use of serotonin reuptake inhibitors prolong the QTc-interval in breast cancer patients treated with tamoxifen?
Concomitant use of tamoxifen and SRIs, particularly paroxetine, escitalopram, and citalopram, significantly prolongs the QTc-interval in breast cancer patients, suggesting venlafaxine may be a safer alternative when co-administration is warranted.
Answers are grounded in this paper and cite their sources.
May warrant QTc monitoring with tamoxifen plus select SRIs; leaves open confirmation of arrhythmia risk in prospective studies.
PURPOSE: Antidepressants like the serotonin reuptake inhibitors (SRIs) are often used concomitantly with tamoxifen (e.g. for treatment of depression). This may lead to an additional prolongation of the QTc-interval, with an increased risk of cardiac side effects. Therefore we investigated whether there is a drug-drug interaction between tamoxifen and SRIs resulting in a prolonged QTc-interval. METHODS: Electrocardiograms (ECGs) of 100 patients were collected at steady state tamoxifen treatment, with or without concomitant SRI co-medication. QTc-interval was manually measured and calculated using the Fridericia formula. Primary outcome was difference in QTc-interval between tamoxifen monotherapy and tamoxifen concomitantly with an SRI. RESULTS: The mean QTc-interval was 12.4 ms longer when tamoxifen was given concomitantly with an SRI (95% CI:1.8-23.1 ms; P = 0.023). Prolongation of the QTc-interval was particularly pronounced for paroxetine (17.2 ms; 95%CI:1.4-33.0 ms; P = 0.04), escitalopram (12.5 ms; 95%CI:4.4-20.6 ms; P < 0.01) and citalopram (20.7 ms; 95%CI:0.7-40.7 ms; P = 0.047), where other agents like venlafaxine did not seem to prolong the QTc-interval. None of the patients had a QTc-interval of >500 ms. CONCLUSIONS: Concomitant use of tamoxifen and SRIs resulted in a significantly higher mean QTc-interval, which was especially the case for paroxetine, escitalopram and citalopram. When concomitant administration with an SRI is warranted venlafaxine is preferred.
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Hussaarts et al. (2019) conducted an observational in Breast cancer (n=100). Serotonin reuptake inhibitors (SRIs) vs. Tamoxifen monotherapy was evaluated on Difference in QTc-interval duration between tamoxifen monotherapy and tamoxifen therapy with concomitant use of SRIs (MD 12.4 ms, 95% CI 1.8-23.1, p=0.023). Concomitant use of tamoxifen and serotonin reuptake inhibitors in breast cancer patients significantly prolonged the mean QTc-interval by 12.4 ms compared to tamoxifen monotherapy.
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