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Controlled Release of Hormones by Pellet Implants
Published in Emmanuel Opara, Controlled Drug Delivery Systems, 2020
Similar to androgens, any molecule that binds to estrogen receptor alpha and/or beta (ERα, ERβ) and influences the physiology of the body is termed as estrogen. Estrogens exert widespread biological functions that reach far beyond their well-known role in reproduction. The effect caused by the molecules that bind to ER could be either positive or negative and hence they may be classified as estrogens or anti-estrogens. Whether the effect is positive or negative, those molecules that modulate the functions of either ERα or ERβ are generally termed as Selective Estrogen Receptor Modulators (SERMs). Exogenous administration of estradiol to ovariectomized experimental animals is of utmost importance in elucidating its mechanism of action. Estrogens are the subject of intensive researches aiming to elucidate their mechanism of action on the various tissues they target (Singh, Meyer, and Simpkins 1995, Jung et al. 2002, Jung et al. 2004, Lee et al. 2004, Dubal et al. 1998, Yang et al. 2001, Simpkins et al. 1997, Wen et al. 2004, Shi et al. 2001, Theodorsson and Theodorsson 2005, Levin-Allerhand, Sokol, and Smith 2003, Gordon et al. 1986, Isaksson et al. 2011, Strom et al. 2010, Bronson 1976, Li et al. 2004, Theodorsson et al. 2005, Strom et al. 2012, Ingberg et al. 2012, Sittadjody et al. 2019, 2017, Singh et al. 2008, Gottardis and Jordan 1988, Gerard et al. 2017, Yang et al. 2015). The use of ready-to-use slow releasing devices to administer steroids, especially estrogens, to small experimental animals remains the method of choice in terms of animal well-being and of safety for both the researcher and the animal. The development of SERMs, as an example tamoxifen, has provided important improvement for the treatment of ER-positive breast cancer (Fontaine et al. 2013, Bachelot et al. 2012). Listed in Table 6.4 are some (if not all) of the estrogens, anti-estrogens, and SERM pellets that are commercially available as ready-to-use sustained-release formulations for the animal research.
Alginate-coated chitosan nanoparticles for pH-dependent release of tamoxifen citrate
Published in Journal of Experimental Nanoscience, 2022
Muhammad Khurram Waqas, Shees Safdar, Manal Buabeid, Akram Ashames, Muhammad Akhtar, Ghulam Murtaza
Tamoxifen is a selective oestrogen receptor modulator (SERM) that is used to treat breast cancer for more than 20 years but it has some limitations due to its serious side effects and low solubility in the water [17]. The anti-estrogenic activity of the tamoxifen depends on location of the tissue and the concentration of the dose [18]. Tamoxifen shows good bioavailability upon oral administration and inhibit binding of oestradiol with the oestrogen receptor as a result oestrogen response is prevented [19]. Oral delivery of tamoxifen is achieved by using its tablets or solution at a dose of 10 mg twice a day [20]; however, it leads to extensive metabolism of tamoxifen in liver [21]. The oral bioavailability of tamoxifen could be enhanced by using its encapsulated formulations, such as microparticles and nanoparticles using suitable polymers. Few studies have already been conducted for the preparation of nanospheres using polyethylene glycol, nanoparticles using poly(-caprolactone), and poly lactide-co-glycolide microspheres. Moreover, chitosan features could also be improved by joining it with other polymers, such as alginate and hyaluronic acid [22].
Overview of biological mechanisms of human carcinogens
Published in Journal of Toxicology and Environmental Health, Part B, 2019
Nicholas Birkett, Mustafa Al-Zoughool, Michael Bird, Robert A. Baan, Jan Zielinski, Daniel Krewski
There is supporting evidence for a non-genotoxic pathway for tamoxifen-induced carcinogenesis in humans. Tamoxifen is a selective estrogen-receptor modulator. In the endometrial endothelium, this drug acts as an agonist, stimulating cellular proliferation. Evidence suggests that the genes targeted by tamoxifen activation of the estrogen receptor differ from those stimulated by estrogen itself. This mechanism may be responsible for the differential action of tamoxifen in distinct tissues, and may contribute to carcinogenicity.
Human exposure to synthetic endocrine disrupting chemicals (S-EDCs) is generally negligible as compared to natural compounds with higher or comparable endocrine activity. How to evaluate the risk of the S-EDCs?
Published in Journal of Toxicology and Environmental Health, Part A, 2020
Herman Autrup, Frank A. Barile, Sir Colin Berry, Bas J. Blaauboer, Alan Boobis, Herrmann Bolt, Christopher J. Borgert, Wolfgang Dekant, Daniel Dietrich, Jose L. Domingo, Gio Batta Gori, Helmut Greim, Jan Hengstler, Sam Kacew, Hans Marquardt, Olavi Pelkonen, Kai Savolainen, Pat Heslop-Harrison, Nico P. Vermeulen
This has been exemplified by the case of diethylstilbestrol (DES), a synthetic non-steroidal selective estrogen receptor modulator (SERM), whose potency is equivalent to or greater than that of ethinyl estradiol (Borgert et al. 2012). In the 1950 s and 1960 s, DES was prescribed to large numbers of pregnant women at massive doses to prevent spontaneous abortions. The administered doses ranged from 5 mg/day up to 125 mg/day (approximately 2 mg/kg-bw/day).