Duloxetine Metabolism and Fibromyalgia Study

This observational study is looking at how the body processes duloxetine (Cymbalta), a common medication for fibromyalgia. Researchers want to understand why some people with fibromyalgia find duloxetine very helpful, while others don't. They will measure the levels of duloxetine in participants' blood and look at certain enzymes (CYP2D6 and CYP1A2) in the liver that break down the drug. This could help doctors better predict who will benefit most from duloxetine, leading to more personalized treatment plans for fibromyalgia. You may be able to join if you are an adult (18+) with a fibromyalgia diagnosis and have been taking duloxetine 60 mg/day for at least 8 weeks. The study aims to enroll 100 participants, but its current recruitment status is unclear.

Study design
This is an observational study, meaning researchers will collect information without giving new treatments. It aims to enroll 100 participants.
What's involved
Participants will have their vital signs (blood pressure, heart rate, oxygen level, temperature, height, weight) taken. You will also fill out a questionnaire about your fibromyalgia and symptoms, and a blood sample will be taken.
Compensation
Not stated in the trial record.
Follow-up
Duloxetine concentrations and enzyme inhibitors/inducers will be measured four hours after your morning duloxetine dose.

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NCT06866444

Duloxetine Metabolism and Fibromyalgia

Recruiting
Not specifiedAges 18+Observational
University of Utah
~100 participants
Updated 2025-08-21 on ClinicalTrials.gov
What's tested:Observational

At a glance

Recruiting sites
1 of 1 listed site is recruiting right now
RecruitingSuspended, closed, or not yet open
What they're measuring
Duloxetine concentrations across metabolizer phenotypes, 3 groups
Measured over Obtained four hours after morning duloxetine dose.
+1 more outcome measured
Fibromyalgia
Duloxetine
1 sites across 1 states
Utah1
  • Jake Steenblick, DNP · PRINCIPAL_INVESTIGATOR · University of Utah

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Eligibility criteria

Inclusion

Adults 18+
Meeting diagnostic criteria for Fibromyalgia
Patients taking Duloxetine 60 mg/day for at least 8 weeks

Exclusion

Pregnant patients per verbal confirmation
Patients that have a history of physician diagnosed kidney or liver disfunction or history of renal dialysis.
Patients requiring an interpreter to communicate
Patient's with progressive illnesses other than fibromyalgia that have a chronic pain and fatigue component (e.g., cancer patients receiving antineoplastic treatment, Parkinson's disease, Multiple Sclerosis).
  • Duloxetine concentrations across metabolizer phenotypes, 3 groupsObtained four hours after morning duloxetine dose.

    Metabolizer phenotypes will be separated into 3 groups based on diplotypes. Ultrarapid metabolizer phenotypes will be measured by having an activity score of greater than 2.0. Normal/intermediate metabolizer phenotypes will be measured by having an activity score between 1.0 to 2.0. Slow metabolizer phenotypes will be measured by having an activity score between 0.75 to 0.

  • Measure inhibitors and inducers of CYP1A2 and CYP2D6 in blood sampleObtained four hours after the morning duloxetine dose.

    Inhibitors and inducers of CYP1A2 and CYP2D6 are defined by the Drug Interaction Flockhart Table. A strong inhibitor will be measured by ≥ 5-fold increase in plasma AUC or more than 80% decrease in clearance. A moderate inhibitor will be measured by 2 to 5-fold increase in the plasma AUC or 50-80% decrease in clearance.