NIH Clinical Research Studies

Protocol Number: 03-EI-0255

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Title:
Pilot Study on the Effect of Vitamin A Supplementation on Cone Function in Retinitis Pigmentosa
Number:
03-EI-0255
Summary:
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.
Sponsoring Institute:
National Eye Institute (NEI)
Recruitment Detail
Type: Participants currently recruited/enrolled
Gender: Male & Female
Referral Letter Required: Yes
Population Exclusion(s): Children

Eligibility Criteria:
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.

Special Instructions:
Currently Not Provided
Keywords:
Retinitis Pigmentosa
Vitamin A
ERG
Recruitment Keyword(s):
Retinitis Pigmentosa
RP
Vitamin A
Condition(s):
Retinitis Pigmentosa
Investigational Drug(s):
Vitamin A
Investigational Device(s):
None
Intervention(s):
Drug: Vitamin A
Supporting Site:
National Eye Institute

Contact(s):
Patient Recruitment and Public Liaison Office
Building 61
10 Cloister Court
Bethesda, Maryland 20892-4754
Toll Free: 1-800-411-1222
TTY: 301-594-9774 (local),1-866-411-1010 (toll free)
Fax: 301-480-9793

Electronic Mail:prpl@mail.cc.nih.gov

Citation(s):
Phelan JK, Bok D. A brief review of retinitis pigmentosa and the identified retinitis pigmentosa genes. Mol Vis. 2000 Jul 8;6:116-24. Review.

Milam AH, Histopathology of the human retina in retinitis pigmentosa. Prog Retin Eye Res. 1998 Apr;17(2):175-205.Review.

Huang PC, Cellular interactions implicated in the mechanism of photoreceptor degeneration in transgenic mice expressing amutant rhodopsin gene. Proc Natl Acad Sci U S A. 1993 Sep 15;90(18):8484-8.

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