{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,8]],"date-time":"2026-07-08T05:26:13Z","timestamp":1783488373375,"version":"3.55.0"},"reference-count":11,"publisher":"SAGE Publications","issue":"6","license":[{"start":{"date-parts":[[2020,6,1]],"date-time":"2020-06-01T00:00:00Z","timestamp":1590969600000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/journals.sagepub.com\/page\/policies\/text-and-data-mining-license"}],"content-domain":{"domain":["journals.sagepub.com"],"crossmark-restriction":true},"short-container-title":["Thyroid\u00ae"],"published-print":{"date-parts":[[2020,6]]},"abstract":"<jats:sec>\n                    <jats:title>Background:<\/jats:title>\n                    <jats:p>\n                      Patients with primary hypothyroidism are treated with levothyroxine (LT4) to normalize their serum thyrotropin (TSH). Finding the optimal dosage is a long-lasting process, and a small change can have major impact. Currently, limited data are available on the impact of dose-equivalent substitution between brands. This study aimed to determine the effect of the shortage of the LT4 brand Thyrax\n                      <jats:sup>\u00ae<\/jats:sup>\n                      in the Netherlands and the resulting dose-equivalent switch to another brand on plasma TSH concentrations in a large cohort of patients.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods:<\/jats:title>\n                    <jats:p>Observational cohort study. Two registries representative for the Dutch population containing prescription and laboratory test data: the Nivel Primary Care Database and the PHARMO Database Network. Patients using at least 25\u2009\u03bcg Thyrax daily for one year or longer were included. Two cohorts were formed: a switch cohort consisting of patients who switched from Thyrax to an alternative brand, and a Thyrax cohort including patients who continued to use Thyrax. Patients in the switch cohort did switch from Thyrax to a different brand of LT4 in 2016 and had two consecutive TSH measurements on the same dose of LT4, one before and one 6 weeks after the switch. Patients in the Thyrax cohort had two consecutive TSH measurements on the same dose of Thyrax that were 6 weeks apart.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results:<\/jats:title>\n                    <jats:p>\n                      In the Thyrax cohort, 19% of euthyroid patients using \u2264100\u2009\u03bcg had a TSH level outside the reference range at the subsequent measurement compared with 24% in the switch cohort (\n                      <jats:italic toggle=\"yes\">p<\/jats:italic>\n                      \u2009&lt;\u20090.0001). For patients using &gt;100\u2009\u03bcg Thyrax, these figures were 24% and 63%, respectively (\n                      <jats:italic toggle=\"yes\">p<\/jats:italic>\n                      \u2009&lt;\u20090.0001). Furthermore, patients using &gt;50\u2009\u03bcg Thyrax were four to five times more likely to become hyperthyroid after a dose-equivalent switch to a different brand compared with patients who stayed on Thyrax.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions:<\/jats:title>\n                    <jats:p>In euthyroid patients continuing the LT4 product Thyrax at the same dose, TSH was out of range in 19\u201324% at least 6 weeks later. A dose-equivalent switch from Thyrax to other LT4 brands induced biochemical signs of overdosing in an even larger proportion (24\u201363%) of patients. The results indicate that a dose-equivalent LT4 brand switch may necessitate a dose adjustment in a large number of patients.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1089\/thy.2019.0414","type":"journal-article","created":{"date-parts":[[2020,3,19]],"date-time":"2020-03-19T02:40:10Z","timestamp":1584585610000},"page":"821-828","update-policy":"https:\/\/doi.org\/10.1177\/sage-journals-update-policy","source":"Crossref","is-referenced-by-count":22,"title":["Impact of a Forced Dose-Equivalent Levothyroxine Brand Switch on Plasma Thyrotropin: A Cohort Study"],"prefix":"10.1177","volume":"30","author":[{"given":"Linda E.","family":"Flinterman","sequence":"first","affiliation":[{"name":"Netherlands Institute for Health Services Research, Nivel, Utrecht, The Netherlands."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Josephina G.","family":"Kuiper","sequence":"additional","affiliation":[{"name":"PHARMO Institute for Drug Outcomes Research, Utrecht, The Netherlands."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Joke C.","family":"Korevaar","sequence":"additional","affiliation":[{"name":"Netherlands Institute for Health Services Research, Nivel, Utrecht, The Netherlands."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Liset","family":"van Dijk","sequence":"additional","affiliation":[{"name":"Netherlands Institute for Health Services Research, Nivel, Utrecht, The Netherlands."},{"name":"Department of PharmacoTherapy, -Epidemiology and -Economics, Groningen Research Institute of Pharmacy, Faculty of Mathematics and Natural Sciences, University of Groningen, Groningen, The Netherlands."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Karin","family":"Hek","sequence":"additional","affiliation":[{"name":"Netherlands Institute for Health Services Research, Nivel, Utrecht, The Netherlands."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Eline","family":"Houben","sequence":"additional","affiliation":[{"name":"PHARMO Institute for Drug Outcomes Research, Utrecht, The Netherlands."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ron","family":"Herings","sequence":"additional","affiliation":[{"name":"PHARMO Institute for Drug Outcomes Research, Utrecht, The Netherlands."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Anton A.M.","family":"Franken","sequence":"additional","affiliation":[{"name":"Medicines Evaluation Board, Utrecht, The Netherlands."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Johan P.","family":"de Graaf","sequence":"additional","affiliation":[{"name":"Dutch Pituitary Foundation, Nijkerk, The Netherlands."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Annemieke","family":"Horikx","sequence":"additional","affiliation":[{"name":"Royal Dutch Pharmacists Association, The Hague, The Netherlands."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Marijke","family":"Janssens","sequence":"additional","affiliation":[{"name":"Dutch Thyroid Patient Organization (SON), Amersfoort, The Netherlands."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Rietje","family":"Meijer","sequence":"additional","affiliation":[{"name":"Dutch Thyroid Patient Organization (SON), Amersfoort, The Netherlands."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Anneke","family":"Wijbenga","sequence":"additional","affiliation":[{"name":"Dutch Thyroid Patient Organization (SON), Amersfoort, The Netherlands."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Eug\u00e8ne","family":"van Puijenbroek","sequence":"additional","affiliation":[{"name":"Department of PharmacoTherapy, -Epidemiology and -Economics, Groningen Research Institute of Pharmacy, Faculty of Mathematics and Natural Sciences, University of Groningen, Groningen, The Netherlands."},{"name":"Netherlands Pharmacovigilance Centre Lareb, 's-Hertogenbosch, The Netherlands."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Bruce H.R.","family":"Wolffenbuttel","sequence":"additional","affiliation":[{"name":"Department of Endocrinology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Thera P.","family":"Links","sequence":"additional","affiliation":[{"name":"Department of Endocrinology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Peter H.","family":"Bisschop","sequence":"additional","affiliation":[{"name":"Department of Endocrinology and Metabolism, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Eric","family":"Fliers","sequence":"additional","affiliation":[{"name":"Department of Endocrinology and Metabolism, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands."}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"179","published-online":{"date-parts":[[2020,6,5]]},"reference":[{"key":"e_1_3_3_2_2","doi-asserted-by":"publisher","DOI":"10.1016\/S0140-6736(17)30703-1"},{"key":"e_1_3_3_3_2","doi-asserted-by":"publisher","DOI":"10.1038\/nrendo.2013.258"},{"key":"e_1_3_3_4_2","doi-asserted-by":"publisher","DOI":"10.1159\/000493123"},{"key":"e_1_3_3_5_2","first-page":"987","article-title":"A follow-up questionnaire: a successful tool to study topics related to packaging changes of the drug Thyrax in the Netherlands","volume":"38","author":"Hartman J","year":"2015","unstructured":"Hartman J, , Weits G, , Rolfes L. 2015. A follow-up questionnaire: a successful tool to study topics related to packaging changes of the drug Thyrax in the Netherlands. 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