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Background: Several case reports have indicated that tamoxifen induced acute pancreatitis (AP); but no pharmacoepidemiological data support the claim. Therefore, we investigated whether tamoxifen use is correlated with the risk of AP in patients with breast cancer. Methods: This population-based cohort study used the Taiwan National Health Insurance Research Database. A cohort of 22 005 patients aged ≥20 years with breast cancer from January 1, 2000 to December 31, 2009 was identified and the date of cancer diagnosis was set as the index date. The end point was developing AP during the follow-up. Hazard ratios (HRs) and 95% confidence intervals (CIs) were evaluated to determine the correlation between the risk of AP and tamoxifen use. Because the drug use varied over time, it was measured as a time-dependent covariate in the Cox proportional hazard model. The same approaches were applied in PS-matched cohorts. Results: After adjustment for covariates and medication use including fluorouracil and doxorubicin, the risk of AP was not significant between tamoxifen users and tamoxifen nonusers (adjusted HR = 0.94, 95% CI = 0.74–1.19) in the non-matching cohorts. The results revealed no dose–response trend between tamoxifen use and the risk of AP (adjusted HR = 0.98, 95% CI = 0.96–1.00). The comorbidities DM and gallstones were associated with a significantly increased risk of AP. Similar trends were observed in PS-matched cohorts. Conclusions: No significant correlation was observed between tamoxifen use and the risk of AP in patients with breast cancer. [ABSTRACT FROM AUTHOR]

Folium Sennae (FS), a popular laxative (Senna), contains polyphenolic anthranoids, whose conjugation metabolites are probable modulators of multidrug resistance-associated proteins (MRPs) and breast cancer resistance protein (BCRP). We suspected that the combined use of FS might alter the pharmacokinetics of various medicines transported by MRPs or BCRP. This study investigated the effect of FS on the pharmacokinetics of methotrexate (MTX), an anticancer drug and a probe substrate of MRPs/BCRP. Rats were orally administered MTX alone and with two dosage regimens of FS in a parallel design. The results show that 5.0 g/kg of FS significantly increased the AUC0–2880, AUC720–2880 and MRT of MTX by 45%, 102% and 42%, and the seventh dose of 2.5 g/kg of FS significantly enhanced the AUC720–2880 and MRT by 78% and 42%, respectively. Mechanism studies indicated that the metabolites of FS (FSM) inhibited MRP 2 and BCRP. In conclusion, the combined use of FS increased the systemic exposure and MRT of MTX through inhibition on MRP 2 and BCRP. [ABSTRACT FROM AUTHOR]