{"id":17533,"date":"2025-10-22T13:52:05","date_gmt":"2025-10-22T06:52:05","guid":{"rendered":"https:\/\/nhathuocngocanh.com\/bp\/?p=17533"},"modified":"2025-10-22T13:52:40","modified_gmt":"2025-10-22T06:52:40","slug":"letrozole","status":"publish","type":"post","link":"https:\/\/nhathuocngocanh.com\/bp\/letrozole\/","title":{"rendered":"Letrozole"},"content":{"rendered":"<p><em>(Ph. Eur. monograph 2334)<\/em><\/p>\n<p>C<sub>17<\/sub>H<sub>11<\/sub>N<sub>5<\/sub> 285.3 112809-51-5<\/p>\n<p><strong>Action and use<\/strong><\/p>\n<p>Aromatase inhibitor; treatment of breast carcinoma.<\/p>\n<p><strong>Preparation<\/strong><\/p>\n<p>Letrozole Tablets<\/p>\n<h2>DEFINITION<\/h2>\n<p>4,4\u2032-[(1H-1,2,4-Triazol-1-yl)methylene]dibenzonitrile.<\/p>\n<h3>Content<\/h3>\n<p>98.0 per cent to 102.0 per cent (anhydrous substance).<\/p>\n<h2>CHARACTERS<\/h2>\n<h3>Appearance<\/h3>\n<p>White or yellowish, crystalline powder.<\/p>\n<h3>Solubility<\/h3>\n<p>Practically insoluble in water, freely soluble in methylene chloride, sparingly soluble in methanol.<\/p>\n<h2>IDENTIFICATION<\/h2>\n<p>Infrared absorption spectrophotometry (2.2.24).<\/p>\n<p>Comparison: letrozole CRS.<\/p>\n<h2>TESTS<\/h2>\n<h3>Related substances<\/h3>\n<p>Liquid chromatography (2.2.29).<\/p>\n<p>Test solution (a): Dissolve 25.0 mg of the substance to be examined in 15 mL of acetonitrile R and dilute to 50.0 mL with water R.<\/p>\n<p>Test solution (b): To 2.0 mL of test solution (a) add 30 mL of acetonitrile R and dilute to 100.0 mL with water R.<\/p>\n<p>Reference solution (a): Dilute 2 mL of test solution (a) to 10 mL with a mixture of 30 volumes of acetonitrile R and 70 volumes of water R. Dissolve the contents of a vial of letrozole impurity A CRS in 1 mL<br \/>\nof this solution.<\/p>\n<p>Reference solution (b): To 2.0 mL of test solution (a) add 30.0 mL of acetonitrile R and dilute to 100.0 mL with water R. To 1.0 mL of this solution add 6.0 mL of acetonitrile R and dilute to 20.0 mL with water R.<\/p>\n<p>Reference solution (c): Dissolve 25.0 mg of letrozole CRS in 15 mL of acetonitrile R and dilute to 50.0 mL with water R. To 2.0 mL of this solution add 30 mL of acetonitrile R and dilute to 100.0 mL with water R.<\/p>\n<p>Column:<\/p>\n<p>\u2014 size: l = 0.125 m, \u00d8 = 4.6 mm;<\/p>\n<p>\u2014 stationary phase: end-capped octadecylsilyl silica gel for chromatography R (5 \u03bcm).<\/p>\n<p>Mobile phase:<\/p>\n<p>\u2014 mobile phase A: water for chromatography R;<\/p>\n<p>\u2014 mobile phase B: acetonitrile for chromatography R;<\/p>\n<table style=\"border-collapse: collapse; width: 100%; height: 84px;\">\n<tbody>\n<tr style=\"height: 21px;\">\n<td style=\"width: 33.3333%; height: 21px; text-align: center;\"><strong>Time<\/strong><\/p>\n<p><strong>(min)<\/strong><\/td>\n<td style=\"width: 33.3333%; height: 21px; text-align: center;\"><strong>Mobile phase A<\/strong><\/p>\n<p><strong>(per cent V\/V)<\/strong><\/td>\n<td style=\"width: 33.3333%; height: 21px; text-align: center;\"><strong>Mobile phase B<\/strong><\/p>\n<p><strong>(per cent V\/V)<\/strong><\/td>\n<\/tr>\n<tr style=\"height: 21px;\">\n<td style=\"width: 33.3333%; height: 21px; text-align: center;\">0 &#8211; 4<\/td>\n<td style=\"width: 33.3333%; height: 21px; text-align: center;\">70<\/td>\n<td style=\"width: 33.3333%; height: 21px; text-align: center;\">30<\/td>\n<\/tr>\n<tr style=\"height: 21px;\">\n<td style=\"width: 33.3333%; height: 21px; text-align: center;\">4 &#8211; 29<\/td>\n<td style=\"width: 33.3333%; height: 21px; text-align: center;\">70 \u2192 30<\/td>\n<td style=\"width: 33.3333%; height: 21px; text-align: center;\">30 \u2192 70<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Flow rate: 1.0 mL\/min.<\/p>\n<p>Detection: Spectrophotometer at 230 nm.<\/p>\n<p>Injection: 20 \u03bcL of test solution (a) and reference solutions (a) and (b).<\/p>\n<p>Identification of impurities: Use the chromatogram obtained with reference solution (a) to identify the peak due to impurity A.<\/p>\n<p>Relative retention: With reference to letrozole (retention time = about 13 min): impurity A = about 0.6.<\/p>\n<p>System suitability: Reference solution (a):<\/p>\n<p>\u2014 resolution: minimum 5.0 between the peaks due to impurity A and letrozole.<\/p>\n<p>Calculation of percentage contents:<\/p>\n<p>\u2014 for each impurity, use the concentration of letrozole in reference solution (b).<\/p>\n<p>Limits:<\/p>\n<p>\u2014 unspecified impurities: for each impurity, maximum 0.10 per cent;<\/p>\n<p>\u2014 total: maximum 0.3 per cent;<\/p>\n<p>\u2014 reporting threshold: 0.05 per cent.<\/p>\n<h3>Water (2.5.12)<\/h3>\n<p>Maximum 0.3 per cent, determined on 1.00 g.<\/p>\n<h2>ASSAY<\/h2>\n<p>Liquid chromatography (2.2.29) as described in the test for related substances with the following modifications.<\/p>\n<p>Injection: Test solution (b) and reference solution (c).<\/p>\n<p>Calculate the percentage content of C<sub>17<\/sub>H<sub>11<\/sub>N<sub>5<\/sub> from the assigned content of letrozole CRS.<\/p>\n<h2>IMPURITIES<\/h2>\n<p>Other detectable impurities (the following substances would, if present at a sufficient level, be detected by one or other of the tests in the monograph. They are limited by the general acceptance criterion for other\/unspecified impurities and\/or by the general monograph Substances for pharmaceutical use (2034). It is therefore not necessary to identify these impurities for demonstration of compliance. See also 5.10.<\/p>\n<p>Control of impurities in substances for pharmaceutical use) A, B.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-medium wp-image-17552\" src=\"https:\/\/nhathuocngocanh.com\/bp\/wp-content\/uploads\/2025\/10\/2-2-300x163.png\" alt=\"Letrozole \" width=\"300\" height=\"163\" srcset=\"https:\/\/nhathuocngocanh.com\/bp\/wp-content\/uploads\/2025\/10\/2-2-300x163.png 300w, https:\/\/nhathuocngocanh.com\/bp\/wp-content\/uploads\/2025\/10\/2-2-1024x555.png 1024w, https:\/\/nhathuocngocanh.com\/bp\/wp-content\/uploads\/2025\/10\/2-2-768x416.png 768w, https:\/\/nhathuocngocanh.com\/bp\/wp-content\/uploads\/2025\/10\/2-2.png 1200w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/p>\n<p>A. 4,4\u2032-[(4H-1,2,4-triazol-4-yl)methylene]dibenzonitrile,<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-medium wp-image-17553\" src=\"https:\/\/nhathuocngocanh.com\/bp\/wp-content\/uploads\/2025\/10\/3-2-300x163.png\" alt=\"Letrozole \" width=\"300\" height=\"163\" srcset=\"https:\/\/nhathuocngocanh.com\/bp\/wp-content\/uploads\/2025\/10\/3-2-300x163.png 300w, https:\/\/nhathuocngocanh.com\/bp\/wp-content\/uploads\/2025\/10\/3-2-1024x555.png 1024w, https:\/\/nhathuocngocanh.com\/bp\/wp-content\/uploads\/2025\/10\/3-2-768x416.png 768w, https:\/\/nhathuocngocanh.com\/bp\/wp-content\/uploads\/2025\/10\/3-2.png 1200w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/p>\n<p>B. 4,4\u2032,4\u2032\u2032-methanetriyltribenzonitrile.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>(Ph. Eur. monograph 2334) C17H11N5 285.3 112809-51-5 Action and use Aromatase inhibitor; treatment of breast carcinoma. Preparation Letrozole Tablets DEFINITION 4,4\u2032-[(1H-1,2,4-Triazol-1-yl)methylene]dibenzonitrile. Content 98.0 per cent to 102.0 per cent (anhydrous substance). CHARACTERS Appearance White or yellowish, crystalline powder. Solubility Practically insoluble in water, freely soluble in methylene chloride, sparingly soluble in methanol. IDENTIFICATION Infrared absorption&#8230;<\/p>\n","protected":false},"author":4,"featured_media":17551,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[174],"tags":[],"class_list":["post-17533","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-medicinal-substances"],"acf":[],"_links":{"self":[{"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/posts\/17533","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/users\/4"}],"replies":[{"embeddable":true,"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/comments?post=17533"}],"version-history":[{"count":3,"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/posts\/17533\/revisions"}],"predecessor-version":[{"id":17560,"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/posts\/17533\/revisions\/17560"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/media\/17551"}],"wp:attachment":[{"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/media?parent=17533"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/categories?post=17533"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/nhathuocngocanh.com\/bp\/wp-json\/wp\/v2\/tags?post=17533"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}