---
title: The Effect of Topiramate on Etonogestrel Concentrations in Contraceptive Implant Users
nct_id: NCT03335163
overall_status: COMPLETED
phase: PHASE1
sponsor: University of Colorado, Denver
study_type: INTERVENTIONAL
primary_condition: Migraine
countries: United States
canonical_url: "https://parkinsonspathways.com/agent/trials/NCT03335163.md"
clinicaltrials_gov: "https://clinicaltrials.gov/study/NCT03335163"
ct_last_update_post_date: 2022-07-13
last_seen_at: "2026-05-12T07:25:39.785Z"
source: ClinicalTrials.gov (mirrored, no enrichment)
---
# The Effect of Topiramate on Etonogestrel Concentrations in Contraceptive Implant Users

**NCT ID:** [NCT03335163](https://clinicaltrials.gov/study/NCT03335163)

## Key Facts

- **Status:** COMPLETED
- **Phase:** PHASE1
- **Study Type:** INTERVENTIONAL
- **Target Enrollment:** 48
- **Lead Sponsor:** University of Colorado, Denver
- **Collaborators:** Merck Sharp & Dohme LLC
- **Conditions:** Migraine, Migraine;Menstrual, Contraception
- **Start Date:** 2018-03-15
- **Completion Date:** 2021-04-22
- **CT.gov Last Update:** 2022-07-13

## Brief Summary

A prospective, non-inferiority study to evaluate the pharmacokinetic effect of topiramate on serum Etonogestrel (ENG) levels in contraceptive implant users.

## Eligibility

- **Minimum age:** 18 Years
- **Maximum age:** 45 Years
- **Sex:** FEMALE
- **Healthy Volunteers:** Yes

```
Inclusion Criteria:

* Healthy women, who have had an ENG implant for 12-36 months at the time of enrollment;
* Will maintain their implant during the study without modifications.

Exclusion Criteria:

* Women who are taking any medications or supplements known to be

  1. Cytochrome P-450 enzyme inducers, inhibitors, or substrates, and
  2. are not willing to abstain from any of these medications or supplements during the entire course of the study.
* Women with liver disease (i.e. hepatitis, fatty liver disease), and
* Women with abnormal liver or renal function, or
* Women with abnormal electrolytes on their screening blood work.
```

## Arms

- **ENG Implant Users** (EXPERIMENTAL) — Healthy women using an ENG implant for at least 12 months and no greater than 36 months will be administered a 6 week titration schedule of topiramate to a max dose of 200mg bid by the final week.

## Interventions

- **Topiramate** (DRUG) — Topiramate - Participants will undergo a 6 week titrated regimen of oral topiramate to reach a maximum dose of 400mg per day:

Week 1 - topiramate PO 25mg daily Week 2 - topiramate PO 25mg twice daily Week 3 - topiramate PO 50mg twice daily Week 4 - topiramate PO 100mg twice daily Week 5 - topiramate PO 150mg twice daily Week 6 - topiramate PO 200mg twice daily

## Primary Outcomes

- **Serum Etonogestrel Concentrations** _(time frame: Enrollment (Baseline), 4 weeks (Visit 2), 5 weeks (Visit 3), 6 weeks (Visit 4))_ — The investigators will collect serum from participants at enrollment and at each of the three study follow-up visits. All samples will be batched for analysis. Analysis will be performed using a liquid-chromatography mass-spectrometry validated assay for measurement of serum etonogestrel concentration.

## Locations (1)

- University of Colorado Denver, Aurora, Colorado, United States

## Recent Field Changes (last 30 days)

- `status.overallStatus` — added _(2026-05-12)_
- `status.primaryCompletionDate` — added _(2026-05-12)_
- `status.completionDate` — added _(2026-05-12)_
- `status.lastUpdatePostDate` — added _(2026-05-12)_
- `design.phases` — added _(2026-05-12)_
- `design.enrollmentCount` — added _(2026-05-12)_
- `eligibility.criteria` — added _(2026-05-12)_
- `eligibility.minAge` — added _(2026-05-12)_
- `eligibility.maxAge` — added _(2026-05-12)_
- `eligibility.sex` — added _(2026-05-12)_
- `outcomes.primary` — added _(2026-05-12)_
- `armsInterventions.arms` — added _(2026-05-12)_
- `armsInterventions.interventions` — added _(2026-05-12)_
- `sponsor.lead` — added _(2026-05-12)_
- `sponsor.collaborators` — added _(2026-05-12)_
- `results.hasResults` — added _(2026-05-12)_
- `locations.university of colorado denver|aurora|colorado|united states` — added _(2026-05-12)_

---

*Canonical: https://parkinsonspathways.com/agent/trials/NCT03335163.md*  
*Source data (authoritative): https://clinicaltrials.gov/study/NCT03335163*  
*This page is a raw mirror with no AI summary, no editorial enrichment, and no Parkinson's-specific filtering.*