Investigating the Effect of Vitamin A Supplementation on Retinitis Pigmentosa

June 30, 2017 updated by: National Eye Institute (NEI)

Pilot Study on the Effect of Vitamin A Supplementation on Cone Function in Retinitis Pigmentosa

Retinitis pigmentosa (RP) is a collective term for a group of inherited retinal dystrophies that are a major cause of irreversible blindness. RP of some type occurs in approximately 1 out of 3500 persons in the United States(1). Gene mutations are responsible for the majority of RP. To date, mutations have been identified in 30 different genes linked to RP(2). The visual prognosis of RP is poor, since the gradual but relentless visual field loss leads eventually to some degree of blindness(3). Although no effective treatment for RP has been identified, participants supplemented with a daily oral dose of 15,000 IU vitamin A palmitate have shown, on average, a slower rate of deterioration of retinal function when the intervention is continued over several years(4). The purpose of this research is to determine whether administration of high oral doses of vitamin A can acutely improve cone photoreceptor function in RP participants as measured by electroretinography (ERG). In this interventional, non-randomized, prospective, pilot study, 5 participants will receive a daily oral dose of 50,000 IU of vitamin A palmitate for 4 weeks, followed by a maintenance dose of 15,000 IU daily for the subsequent 2 weeks. The primary efficacy outcome is a relative percentage change in ERG response amplitude subsequent to vitamin A supplementation. A secondary efficacy outcome is a relative percentage change in implicit time from pre- to post- vitamin A supplementation, with improvement specified as a shorter response implicit time. Other secondary outcomes will be improvements in visual field (Humphery, 10-2; sum of thresholds). Safety outcomes include visual fields, ETDRS visual acuity, intraocular pressure, serum vitamin A level and liver function tests.

Study Overview

Status

Completed

Intervention / Treatment

Detailed Description

Retinitis pigmentosa (RP) is a collective term for a group of inherited retinal dystrophies that are a major cause of irreversible blindness. RP of some type occurs in approximately 1 out of 3500 persons in the United States. Gene mutations are responsible for the majority of RP. To date, mutations have been identified in 30 different genes linked to RP. The visual prognosis of RP is poor, since the gradual but relentless visual field loss leads eventually to some degree of blindness. Although no effective treatment for RP has been identified, participants supplemented with a daily oral dose of 15,000 IU vitamin A palmitate have shown, on average, a slower rate of deterioration of retinal function when the intervention is continued over several years. The purpose of this research is to determine whether administration of high oral doses of vitamin A can acutely improve cone photoreceptor function in RP participants as measured by electroretinography (ERG). In this interventional, non-randomized, prospective, pilot study, 10 participants (five with the RHO1 gene mutation and five without the mutation) will receive a daily oral dose of 50,000 IU of vitamin A palmitate for 4 weeks, followed by a maintenance dose of 15,000 IU daily for the subsequent 2 weeks. The primary efficacy outcome is a relative percentage change in ERG response amplitude subsequent to vitamin A supplementation. A secondary efficacy outcome is a relative percentage change in implicit time from pre- to post- vitamin A supplementation, with improvement specified as a shorter response implicit time. Other secondary outcomes will be improvements in visual field (Humphrey 10-2; sum of thresholds). Safety outcomes include visual fields, ETDRS visual acuity, intraocular pressure, serum vitamin A level and liver function tests.

Study Type

Interventional

Enrollment

11

Phase

  • Phase 1

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

    • Maryland
      • Bethesda, Maryland, United States, 20892
        • National Institutes of Health Clinical Center, 9000 Rockville Pike

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

18 years and older (Adult, Older Adult)

Accepts Healthy Volunteers

No

Genders Eligible for Study

All

Description

  • INCLUSION CRITERIA:

All participants must meet the following criteria to participate in the study.

  1. Men and women age 18 years of age and older. (Children will be excluded since there is a higher incidence of vitamin A toxicity in the pediatric population.)
  2. Diagnoses of typical RP of all genetic subtypes (simplex, autosomal dominant, autosomal recessive, and X-linked), as determined primarily by abnormally reduced ERG rod response amplitudes that are relatively more affected than cone ERG amplitudes.
  3. Mutation in the RHO1 gene as determined by genotyping.
  4. Participants in whom flicker ERG can be measured reliably (standard flicker ERG amplitude greater than 2 microV).
  5. Willingness to use contraception for the duration of the study.
  6. Understood and signed consent.

EXCLUSION CRITERIA:

Participants with the following conditions will be excluded from study.

  1. Participants with syndromic RP (i.e., Ushers syndrome).
  2. Have abnormal liver function (greater than ULN ALT, AST, Alkaline Phosphate, or Total Bilirubin).
  3. Hematocrit greater than 1.5 x ULN
  4. Have abnormal kidney function (greater than1.5 mg/dL serum creatinine).
  5. Currently or has taken greater than 15,000 IU/day vitamin A supplementation within 6 months of the first screening visit.
  6. Is pregnant or lactating (due to evidence that sugests excessive intake of vitamin A could be tertogenic in humans and affect the content of breast milk).
  7. Currently or has taken greater than 400 IU/day of vitamin E supplementation within 6 months of enrollment.
  8. Vitamin A serum level exceeding 150 microg/dL.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start

July 17, 2003

Study Completion

May 6, 2009

Study Registration Dates

First Submitted

July 23, 2003

First Submitted That Met QC Criteria

July 23, 2003

First Posted (Estimate)

July 24, 2003

Study Record Updates

Last Update Posted (Actual)

July 2, 2017

Last Update Submitted That Met QC Criteria

June 30, 2017

Last Verified

May 6, 2009

More Information

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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