{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,28]],"date-time":"2026-09-28T19:31:30Z","timestamp":1790623890450,"version":"4.1.0"},"reference-count":23,"publisher":"MDPI AG","issue":"15","license":[{"start":{"date-parts":[[2025,7,24]],"date-time":"2025-07-24T00:00:00Z","timestamp":1753315200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Faculty of Medicine Endowment Fund for medical research, Faculty of Medicine, Chiang Mai University"},{"name":"Berlin Pharmaceutical Industry Co. Ltd."}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["JCM"],"abstract":"<jats:p>Background: Direct oral anticoagulants (DOACs) are generally preferred over warfarin for preventing arterial and venous thromboembolism. However, the efficacy and safety of DOACs in patients with extremely low body weight (BW) are uncertain. This study investigates anti-factor Xa (anti-FXa) activity of apixaban and compares it between patients with normal BW (&gt;50 kg) and underweight (\u226450 kg). Methods: We enrolled 150 patients on branded generic apixaban (ApixanTM) for atrial fibrillation (AF), venous thromboembolism, and intracardiac thrombus. Anti-FXa activity of apixaban was measured at peak concentration (Cpeak) and trough concentration (Ctrough) after at least one week of therapy. Results: Mean age was 64.0 \u00b1 12.7 years, with 53.3% being male. Mean BW was 61.3 \u00b1 15.3 kg. Of the 150 patients, 132 (88%) had AF, and 43 (28.7%) had low BW. Overall, 87.3% and 84.7% of patients had Ctrough and Cpeak within the expected range. Underweight patients had significantly higher mean Ctrough and Cpeak than normal BW patients. A higher proportion of low-BW patients exceeded the expected Cpeak range compared to normal-BW patients (25.6% vs. 3.7%, p &lt; 0.001). Low BW was the only independent predictor of exceeding Cpeak specified range (adjusted OR 4.87, 95% CI 1.31\u201318.15, p = 0.018). Conclusions: Most patients maintained apixaban levels within expected ranges, but those with low BW were more likely to exceed the specified range of Cpeak.<\/jats:p>","DOI":"10.3390\/jcm14155238","type":"journal-article","created":{"date-parts":[[2025,7,24]],"date-time":"2025-07-24T10:28:09Z","timestamp":1753352889000},"page":"5238","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Anti-Factor Xa Activity of Apixaban in Extremely Low Body Weight"],"prefix":"10.3390","volume":"14","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-2418-329X","authenticated-orcid":false,"given":"Wanwarang","family":"Wongcharoen","sequence":"first","affiliation":[{"name":"Division of Cardiology, Department of Internal Medicine, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Amarase","family":"Pamarapa","sequence":"additional","affiliation":[{"name":"Division of Cardiology, Department of Internal Medicine, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2158-1444","authenticated-orcid":false,"given":"Siriluck","family":"Gunaparn","sequence":"additional","affiliation":[{"name":"Division of Cardiology, Department of Internal Medicine, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3986-1951","authenticated-orcid":false,"given":"Arintaya","family":"Phrommintikul","sequence":"additional","affiliation":[{"name":"Division of Cardiology, Department of Internal Medicine, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,7,24]]},"reference":[{"key":"ref_1","first-page":"270","article-title":"Prevalence of atrial fibrillation in Thai elderly","volume":"13","author":"Phrommintikul","year":"2016","journal-title":"J. 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