Research Article Effect of Short-Course Oral Ciprofloxacin on Isoflavone Pharmacokinetics following Soy Milk Ingestion in Healthy Postmenopausal Women Nathathai Temyingyong , 1 Nut Koonrungsesomboon , 2,3 Nutthiya Hanprasertpong , 2 Mingkwan Na Takuathung , 2 and Supanimit Teekachunhatean 2,4 1 Graduate School, Chiang Mai University, Chiang Mai 50200, ailand 2 Department of Pharmacology, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, ailand 3 Musculoskeletal Science and Translational Research (MSTR), Chiang Mai University, Chiang Mai 50200, ailand 4 Center of ai Traditional and Complementary Medicine, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, ailand Correspondence should be addressed to Supanimit Teekachunhatean; supanimit.t@cmu.ac.th Received 7 November 2018; Revised 16 March 2019; Accepted 21 March 2019; Published 11 April 2019 Guest Editor: Xinguang Liu Copyright © 2019 Nathathai Temyingyong et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Soy isofavones have several potential benefts related to postmenopausal health. Isofavone glycosides, found predominantly in nonfermented soy products, e.g., soy milk, require conversion by gut microbiota to their respective bioavailable aglycones prior to absorption into portal circulation. Use of short-course oral ciprofoxacin for the treatment of acute uncomplicated cystitis, the incidence of which is increasing among postmenopausal women, might adversely afect gut microbiota. Te objective of this one- group pre-post treatment study was to determine the efect of short-course oral ciprofoxacin on isofavone pharmacokinetics in healthy postmenopausal women. Eleven postmenopausal subjects were assigned to consume a single oral dose of 375 mL UHT soy milk (SOY phase). Blood samples were collected immediately before soy milk ingestion and at specifc times for 32 hours afer soy milk ingestion. Following a washout period of at least seven days, subjects were assigned to take 250 mg oral ciprofoxacin afer breakfast and dinner for three days, followed by a single oral dose of 375 mL UHT soy milk the next day (CIPRO/SOY phase). Blood samples were collected at the same time points as in the SOY phase. Plasma samples were treated with -glucuronidase/sulfatase and plasma concentrations of aglycones (genistein and daidzein) were determined using high-performance liquid chromatography. C max , AUC 0-t , and AUC 0-∞ of both aglycones and T max of genistein obtained from the CIPRO/SOY phase were signifcantly lower than those obtained from the SOY phase, while T max of daidzein and t 1/2 of both aglycones in the two phases were not signifcantly diferent. 1. Introduction Soy isofavones, nonsteroidal polyphenolic compounds found in soybeans [1], are structurally similar to 17-estradiol and have estrogen-like efects [2, 3]. Evidence suggests that soy isofavones have several potential benefts related to women’s health, such as relief of postmenopausal vasomotor symptoms [4] as well as prevention of estrogen-related cancer [5–7], cardiovascular disease [8, 9], and osteoporosis [10, 11]. Soy isofavones occur in three aglycone structures (daid- zein, genistein, and glycitein), which can enter into three - glycoside conjugates (daidzin, genistin, and glycitin), each with its corresponding acetyl- and malonyl-glycoside conju- gates. As glycitein and its glycoside conjugates account for less than 5-10% of the total isofavones in soy-based products, most studies have focused on daidzein and genistein and their respective glycoside conjugates [12]. Te popularity of soy milk consumption is increasing worldwide because soy milk is an important beverage source of isofavones [13]. It is also the preferred alternative to cow’s milk for individuals with lactose intolerance [13]. Regular consumption of isofavone-rich soy milk alleviates climacteric symptoms (both somatic and urogenital domain symptoms) in peri- and postmenopausal women [14] and Hindawi Evidence-Based Complementary and Alternative Medicine Volume 2019, Article ID 7192326, 10 pages https://doi.org/10.1155/2019/7192326