{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,6]],"date-time":"2026-10-06T13:56:00Z","timestamp":1791294960890,"version":"4.1.0"},"reference-count":20,"publisher":"Wiley","license":[{"start":{"date-parts":[[2026,10,6]],"date-time":"2026-10-06T00:00:00Z","timestamp":1791244800000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"},{"start":{"date-parts":[[2026,10,6]],"date-time":"2026-10-06T00:00:00Z","timestamp":1791244800000},"content-version":"tdm","delay-in-days":0,"URL":"http:\/\/doi.wiley.com\/10.1002\/tdm_license_1.1"}],"funder":[{"DOI":"10.13039\/100000050","name":"National Heart, Lung, and Blood Institute","doi-asserted-by":"publisher","award":["DP1HL174180"],"award-info":[{"award-number":["DP1HL174180"]}],"id":[{"id":"10.13039\/100000050","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000060","name":"National Institute of Allergy and Infectious Diseases","doi-asserted-by":"publisher","award":["P30AI036219"],"award-info":[{"award-number":["P30AI036219"]}],"id":[{"id":"10.13039\/100000060","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100000052","name":"NIH Office of the Director","doi-asserted-by":"publisher","award":["S10OD028540"],"award-info":[{"award-number":["S10OD028540"]}],"id":[{"id":"10.13039\/100000052","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Br J Clin Pharmacol"],"abstract":"<jats:p>Lenacapavir (LEN), a first\u2010in\u2010class capsid inhibitor, has unique pharmacokinetics that enable twice\u2010yearly dosing. LEN is not extensively metabolized, although it is a substrate of CYP3A4, which introduces drug\u2013drug interactions concerns. As adoption and implementation of LEN for treatment and prevention increase, additional guidance on concomitant medications with LEN is needed. Primidone is a barbiturate type anticonvulsant medication and a moderate\u2010to\u2010strong inducer of CYP3A4. A primary metabolite of primidone, phenobarbital, also induces CYP3A. Consequently, the coadministration of LEN and primidone is not recommended due to the potential induction of CYP3A\u2010mediated metabolism and resultant subtherapeutic LEN concentrations. However, the extent to which LEN concentrations may decrease alongside concomitant primidone is unknown. Herein, we describe a 67\u2010year\u2010old male initiating LEN following switch from a boosted darunavir regimen, alongside long\u2010standing treatment with primidone 50\u2009mg daily. Blood samples were collected throughout the first 6\u2010month dosing interval. Plasma LEN concentrations were quantified using a validated liquid chromatography\u2013tandem mass spectrometry analytical method. LEN concentrations remained above four times the protein adjusted 95% effective concentration during the measured time points. The lowest observed concentration was 24.9\u00a0ng\/mL at Month 1; the highest observed was 58.3\u00a0ng\/mL at Month 3. The projected 6\u2010month concentration was 40.6\u00a0ng\/mL. Observed concentrations were generally consistent with concentrations reported in prior studies in the absence of clinically\u2010significant drug\u2013drug interactions. Viral load measures remained undetectable throughout the dosing interval and following subsequent administrations thereafter. This case provides pharmacokinetic rationale for the coadministration of LEN with primidone and may help guide future clinical decision\u2010making.<\/jats:p>","DOI":"10.1002\/bcp.70873","type":"journal-article","created":{"date-parts":[[2026,10,6]],"date-time":"2026-10-06T13:08:26Z","timestamp":1791292106000},"source":"Crossref","is-referenced-by-count":0,"title":["Lenacapavir initiation with concomitant primidone: A case report with therapeutic drug monitoring"],"prefix":"10.1002","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-2778-3725","authenticated-orcid":false,"given":"Aaron S.","family":"Devanathan","sequence":"first","affiliation":[{"name":"Center for Clinical Pharmaceutical Sciences, Department of Pharmacy and Therapeutics, School of Pharmacy University of Pittsburgh  Pittsburgh Pennsylvania USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Thomas","family":"Glowa","sequence":"additional","affiliation":[{"name":"Department of Medicine, School of Medicine University of Pittsburgh  Pittsburgh Pennsylvania USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Emily M.","family":"Thompson","sequence":"additional","affiliation":[{"name":"Center for Clinical Pharmaceutical Sciences, Department of Pharmacy and Therapeutics, School of Pharmacy University of Pittsburgh  Pittsburgh Pennsylvania USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Amanda J.","family":"Saylor","sequence":"additional","affiliation":[{"name":"Department of Medicine, School of Medicine University of Pittsburgh  Pittsburgh Pennsylvania USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4339-1382","authenticated-orcid":false,"given":"Thomas D.","family":"Nolin","sequence":"additional","affiliation":[{"name":"Center for Clinical Pharmaceutical Sciences, Department of Pharmacy and Therapeutics, School of Pharmacy University of Pittsburgh  Pittsburgh Pennsylvania USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sharon A.","family":"Riddler","sequence":"additional","affiliation":[{"name":"Department of Medicine, School of Medicine University of Pittsburgh  Pittsburgh Pennsylvania USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ken S.","family":"Ho","sequence":"additional","affiliation":[{"name":"Department of Medicine, School of Medicine University of Pittsburgh  Pittsburgh Pennsylvania USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2026,10,6]]},"reference":[{"key":"e_1_2_9_2_1","doi-asserted-by":"publisher","DOI":"10.1056\/NEJMoa2115542"},{"key":"e_1_2_9_3_1","doi-asserted-by":"publisher","DOI":"10.1056\/NEJMoa2407001"},{"key":"e_1_2_9_4_1","doi-asserted-by":"publisher","DOI":"10.1021\/acs.molpharmaceut.3c00626"},{"key":"e_1_2_9_5_1","doi-asserted-by":"publisher","DOI":"10.1007\/s40262\u2010023\u201001328\u20101"},{"key":"e_1_2_9_6_1","unstructured":"Gilead Sciences Inc.SUNLENCA package insert. Published2022. Accessed April 16 2023.https:\/\/www.gilead.com\/-\/media\/files\/pdfs\/medicines\/hiv\/sunlenca\/sunlenca_pi.pdf"},{"key":"e_1_2_9_7_1","doi-asserted-by":"publisher","DOI":"10.1002\/cpt.3447"},{"key":"e_1_2_9_8_1","volume-title":"StatPearls","author":"Lenkapothula N","year":"2022"},{"key":"e_1_2_9_9_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.jchromb.2023.123905"},{"key":"e_1_2_9_10_1","doi-asserted-by":"publisher","DOI":"10.1038\/s41586\u2010020\u20102443\u20101"},{"key":"e_1_2_9_11_1","doi-asserted-by":"publisher","DOI":"10.1111\/bph.16181"},{"key":"e_1_2_9_12_1","unstructured":"University of Liverpool.Liverpool HIV interactions. Published2026. Accessed July 30 2026.https:\/\/www.hiv-druginteractions.org\/checker"},{"key":"e_1_2_9_13_1","unstructured":"Gilead Sciences Inc.YEZTUGO package insert. Published2025. Accessed June 22 2025.https:\/\/www.accessdata.fda.gov\/drugsatfda_docs\/label\/2025\/220020s000lbl.pdf"},{"key":"e_1_2_9_14_1","doi-asserted-by":"publisher","DOI":"10.1128\/AAC.01564\u201009"},{"key":"e_1_2_9_15_1","unstructured":"National Health Service.Understanding enzyme or transporter\u2010based drug interactions. Published May 22 2024. Accessed August 11 2026.https:\/\/sps.nhs.uk\/articles\/understanding-enzyme-or-transporter-based-drug-interactions\/"},{"key":"e_1_2_9_16_1","doi-asserted-by":"publisher","DOI":"10.1111\/j.1365\u20102125.1984.tb02482.x"},{"key":"e_1_2_9_17_1","doi-asserted-by":"publisher","DOI":"10.1203\/00006450\u2010198510000\u201000300"},{"key":"e_1_2_9_18_1","doi-asserted-by":"publisher","DOI":"10.1111\/j.1651\u20102227.1991.tb11744.x"},{"key":"e_1_2_9_19_1","doi-asserted-by":"publisher","DOI":"10.1177\/00185787221150928"},{"key":"e_1_2_9_20_1","doi-asserted-by":"publisher","DOI":"10.1002\/phar.70133"},{"key":"e_1_2_9_21_1","unstructured":"ImperialM HughesE PanchiaRet al.Population pharmacokinetic analysis of lenacapavir in people who want or need pre exposure prophylaxis for HIV [abstract I\u2010109]. Presented at the: Population Approach Group Europe (PAGE) Meeting; June 4 2025. Accessed July 29 2026.https:\/\/www.page-meeting.org\/wp-content\/uploads\/pdf_abstracts\/2025\/11420.pdf"}],"container-title":["British Journal of Clinical Pharmacology"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/bpspubs.onlinelibrary.wiley.com\/doi\/pdf\/10.1002\/bcp.70873","content-type":"application\/pdf","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/bpspubs.onlinelibrary.wiley.com\/doi\/full-xml\/10.1002\/bcp.70873","content-type":"application\/xml","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/bpspubs.onlinelibrary.wiley.com\/doi\/pdf\/10.1002\/bcp.70873","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,10,6]],"date-time":"2026-10-06T13:08:29Z","timestamp":1791292109000},"score":1,"resource":{"primary":{"URL":"https:\/\/bpspubs.onlinelibrary.wiley.com\/doi\/10.1002\/bcp.70873"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,10,6]]},"references-count":20,"alternative-id":["10.1002\/bcp.70873"],"URL":"https:\/\/doi.org\/10.1002\/bcp.70873","archive":["Portico"],"relation":{},"ISSN":["0306-5251","1365-2125"],"issn-type":[{"value":"0306-5251","type":"print"},{"value":"1365-2125","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,10,6]]},"article-number":"bcp.70873"}}