{"doi":"10.1002/cpt.3642","title":"Changes in <i>S</i>‐Citalopram Plasma Concentrations Across Pregnancy and Postpartum","abstract":"Major depressive disorder is a common disorder in pregnancy. Although citalopram/escitalopram is the second most frequently prescribed antidepressant for pregnant people, information about its pharmacokinetics in pregnancy is limited. We investigated plasma (S)-citalopram concentration to dose (C/D) ratios across pregnancy and postpartum and the effect of pharmacogenetics on its elimination. This prospective observational cohort study enrolled 30 participants with a singleton pregnancy who chose to continue citalopram/escitalopram during pregnancy for a prior diagnosis of major depression. Monthly blood samples were obtained 24 hours post-dose across pregnancy and twice postpartum for measurement of plasma citalopram, desmethylcitalopram, and didesmethylcitalopram enantiomer concentrations. Compared with the 36-week reference, (S)-citalopram C/D ratios were not significantly different throughout pregnancy. However, the mean (S)-citalopram C/D ratio was elevated by 63% (P < 0.001) 6 to 8 weeks after delivery before it decreased to a mean C/D ratio in the later post-birth period that was marginally different than at 36 weeks (1.20 ± 0.64 vs. 0.92 ± 0.46, respectively; P = 0.06). Analyzing the results by cytochrome P 450 (CYP) 2C19 phenotype, the mean late postpartum (S)-citalopram concentration to dose ratio in intermediate metabolizers was approximately twice that in extensive, rapid, or ultrarapid metabolizers. However, at the 36-week reference point, the mean concentration to dose ratio in pregnant CYP2C19 intermediate metabolizers was 35.7% lower than the distant postpartum ratio, while the ratios in extensive and rapid/ultrarapid metabolizers were 15.4% and 18.5% lower, respectively. Without dose adjustment, people with intermediate or poor CYP2C19 activity may be at risk for subtherapeutic S-citalopram concentrations during pregnancy.","journal":"Clinical Pharmacology & Therapeutics","year":2025,"id":530527,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":5,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9465,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2025-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":384823,"name":"Michael J. Avram","orcid":"0000-0001-6637-1355","position":1,"is_corresponding":false},{"id":321394,"name":"Alfred L. George","orcid":"0000-0002-3993-966X","position":2,"is_corresponding":false},{"id":713392,"name":"Amy Yang","orcid":"0000-0002-4763-7741","position":3,"is_corresponding":false},{"id":446991,"name":"Jody D. Ciolino","orcid":"0000-0002-9060-5657","position":4,"is_corresponding":false},{"id":949980,"name":"Hyunyoung Jeong","orcid":"0000-0001-7769-7676","position":5,"is_corresponding":false},{"id":331591,"name":"Raman Venkataramanan","orcid":"0000-0003-1893-3290","position":6,"is_corresponding":false},{"id":331590,"name":"Steve N. Caritis","orcid":"0000-0002-2169-0712","position":7,"is_corresponding":false},{"id":317452,"name":"Maged M. Costantine","orcid":"0000-0003-4076-469X","position":8,"is_corresponding":false},{"id":601130,"name":"Katherine L. Wisner","orcid":"0000-0003-3458-5986","position":9,"is_corresponding":false},{"id":607664,"name":"Catherine S. Stika","orcid":"0000-0001-7186-1877","position":0,"is_corresponding":true}],"reference_count":48,"raw_metadata":null,"created_at":"2026-07-19T02:51:05.836974Z","pmid":"40099712","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}