ArticleObstetrics and gynecology2022
Effect of Topiramate on Serum Etonogestrel Concentrations Among Contraceptive Implant Users.
Article in Obstetrics and gynecology, 2022. The graph could read no effect estimate from its abstract, so it casts no vote on the map. It is linked to trial NCT03335163 (The Effect of Topiramate on Etonogestrel Concentrations in Contraceptive Implant Users), which is not on this map. Cited by 5 papers, 1 of them a synthesis that pooled it.
What it found
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The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
The Effect of Topiramate on Etonogestrel Concentrations in Contraceptive Implant Users
Who cites it
5 citing papers in PubMed, 1 synthesis or guideline pooled it, 26 citations in OpenAlex.
- European Headache Federation (EHF) critical reappraisal and meta-analysis of oral drugs in migraine prevention - part 3: topiramate.The journal of headache and pain · 2023Pooled it
- Contraceptive management in people with epilepsy: A narrative review of drug interactions, special populations, and clinical guidance.Epileptic disorders : international epilepsy journal with videotape · 2026Review
- Counseling Reproductive-Age Youth With Epilepsy: Literature Review and Expert Opinion From the Epilepsy in the Child-Bearing Ages Through Menopause Consortium.Pediatric neurology · 2026Review
- Estimating risk of reported versus theoretical drug-drug interactions in headaches medicine: an exhaustive comparison between DrugBank and FAERS database for abortive and preventive combinations.Journal of oral & facial pain and headache · 2025Article
- Knowledge, Attitudes, and Decision-Making About Reproductive Health and Epilepsy: A Survey of Health Care Providers and Women With Epilepsy.Neurology. Clinical practice · 2025Article
Corrections and comments
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Authors and funding
4 authors at 1 institution in 1 country.
Funding
Abstract
objectiveTo evaluate topiramate and etonogestrel pharmacokinetic interactions in contraceptive implant users.
methodsWe conducted a prospective, noninferiority study with healthy women using etonogestrel implants continuously for 12-36 months. We measured baseline serum etonogestrel concentrations and then began a 6-week titrated topiramate regimen to standard migraine (100 mg/day) and epilepsy (400 mg/day) dosages. We repeated serum etonogestrel concentrations at 3 weeks (100 mg/day), 4 weeks (200 mg/day), and 6 weeks (400 mg/day) of topiramate therapy. We measured etonogestrel using a validated liquid chromatography-tandem, mass-spectrometry assay and tested for noninferiority (less than 30% decrease) in serum etonogestrel concentrations from baseline.
resultsWe enrolled 48 total participants; 32 completed 3 weeks, 31 completed 4 weeks, and 27 completed all follow-up visits. Participants' median age was 25.3 years (range 18.3-37.2), median body mass index (BMI) was 25.5 kg/m2 (range 18.7-42.2), and median duration of implant use was 24 months (range 12-36). Median etonogestrel concentrations were 142 pg/mL (range 76.2-771) at baseline, 126 pg/mL (range 72.4-585) at 3 weeks, 119 pg/mL (range 65.6-542) at 4 weeks, and 105 pg/mL (46.2-859) at 6 weeks. The 95% CIs for mean percent change in serum etonogestrel concentrations from baseline were [-37.3%+16.9%], [-45.4%+5.2%], and [-66.8%+24.8%] at 3 weeks, 4 weeks, and 6 weeks, respectively. Excluding one participant who had a serum etonogestrel concentration less than 90 pg/mL at baseline, 30.8% of participants (8/26, 95% CI 14.3-51.8%) had a serum etonogestrel concentration less than 90 pg/mL at 6 weeks.
conclusionThough only a mild enzyme-inducing antiepileptic drug, concomitant topiramate use led to inferior serum etonogestrel concentrations among implant users, with a significant proportion reaching etonogestrel concentrations below the threshold for ovulatory suppression when taking antiepileptic dosages of topiramate. FUNDING SOURCE: This study was primarily funded through an Investigator-Initiated Study grant from Merck Sharp & Dohme Corp [MISP#57073]. This work was also supported by NIH/NCATS CTSA Grant Number UL1 TR001082 and NICHD K12 Women's Reproductive Health Research Scholar Program (grant number 5K12HD001271-18). CLINICAL
trial registrationClinicalTrials.gov, NCT03335163.
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Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.