Levodopa for Diabetic Retinopathy

The purpose of this study is to determine optimum dosing strategies of levodopa and determine the physiologic mechanisms that provide the therapeutic response to restore abnormalities in the electrical conductivity of the retina in people with diabetes and no clinically visible retinopathy.

Study Overview

• Status: Completed
• Conditions: Diabetic Retinopathy
• Intervention / Treatment: Drug: Placebo; Drug: Levodopa

Detailed Description

This study is investigating the optimal timing of using levodopa in reducing damage in the retina from diabetes mellitus. Adult subjects will be recruited from the Atlanta VA Eye clinic and randomized to one of four arms: placebo, levodopa every other day, levodopa daily, or levodopa twice daily. Each group include participants that will receive treatment for 6 months with eye exams and testing conducted at baseline, 3 month, and 6 month visits. Testing at the visits includes electroretinograms, fundus photography, optical coherence tomography with angiography, and HbA1c serology. Veterans will sign the consent, in-person prior to beginning study activities.

• Study Type: Interventional
• Enrollment (Actual): 230
• Phase: Phase 2

Contacts and Locations

Study Locations

• United States
  • Georgia
    • Decatur, Georgia, United States, 30033
      • Atlanta VA Medical Center

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Adults
• diagnosed with diabetes mellitus

Exclusion Criteria:

• taking dopamine effecting drugs
• have a pituitary tumor
• psychosis, Parkinson's disease
• cognitive deficits
• confounding ocular disease

Control Participants:

Non-diabetic participants with no visual problems to create control measurements.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Double

Number of Arms

4

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Placebo; Diabetic participants will be instructed to take the oral placebo daily with a meal for 6 months.	Drug: Placebo; Patients will receive matching placebo tablets as the drug treatment.
Experimental: Levodopa every other day; Diabetic participants will be instructed to take the levodopa every other day with a meal for 6 months.	Drug: Levodopa; Patients will receive tablets of generic 25 mg carbidopa/100 mg levodopa as the drug treatment.
Experimental: Levodopa once per day; Diabetic participants will be instructed to take the oral levodopa daily with a meal for 6 months..	Drug: Levodopa; Patients will receive tablets of generic 25 mg carbidopa/100 mg levodopa as the drug treatment.
Experimental: Levodopa twice per day; Diabetic participants in the twice per day group will be instructed to take the drug 12 hours apart every day for 6 months.	Drug: Levodopa; Patients will receive tablets of generic 25 mg carbidopa/100 mg levodopa as the drug treatment.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
ERG with dim flash stimuli	Full-field electroretinography (ERG) will be performed to assess rod-mediated retinal function. A skin electrode placed below the eye records the response to flash stimuli. Participants will be dark-adapted for 10 minutes to sensitive retinal rod pathways. Flash stimuli will consist of dim (1.13 Td) or bright (85 Td) flashes to reveal early dysfunction in DR.	Baseline, 3 and 6 months post-intervention

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Optical coherence tomography (OCT)	Optical coherence tomography (OCT) will be done with the Heidelberg SLO+HRA to image the retina. The retinal vessels and retinal layers will be analyzed for any abnormalities.	Baseline, 3 and 6 months post-intervention
Optical coherence tomography (OCT-A)	Optical coherence tomography (OCT) will be done with the Heidelberg SLO+HRA with an angiography module to image the retina. Percent of retinal area with perfusion abnormality will be calculated.	Baseline, 3 and 6 months post-intervention

Collaborators and Investigators

• Sponsor: Emory University
• Collaborators: Morningside Center for Innovative and Affordable Medicine
• Investigators: Principal Investigator: Andrew Hendrick, MD, Emory University

Study record dates

Study Major Dates

• Study Start (Actual): April 18, 2022
• Primary Completion (Actual): November 17, 2025
• Study Completion (Actual): November 17, 2025

Study Registration Dates

• First Submitted: February 25, 2026
• First Submitted That Met QC Criteria: February 25, 2026
• First Posted (Actual): March 3, 2026

Study Record Updates

• Last Update Posted (Actual): March 3, 2026
• Last Update Submitted That Met QC Criteria: February 25, 2026
• Last Verified: February 1, 2026

More Information

Terms related to this study

• Keywords: Optical coherence tomography; Electroretinography
• Additional Relevant MeSH Terms: Endocrine System Diseases; Vascular Diseases; Cardiovascular Diseases; Diabetes Mellitus; Eye Diseases; Diabetic Angiopathies; Diabetes Complications; Retinal Diseases; Diabetic Retinopathy; Amino Acids, Peptides, and Proteins; Organic Chemicals; Hydrocarbons; Hydrocarbons, Cyclic; Hydrocarbons, Aromatic; Amines; Amino Acids; Catechols; Phenols; Benzene Derivatives; Phenylalanine; Amino Acids, Aromatic; Amino Acids, Cyclic; Catecholamines; Dihydroxyphenylalanine; Tyrosine; Levodopa
• Other Study ID Numbers: STUDY00002995; 2025P013031 (Other Identifier: Emory IRB)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No