Vitamin A is an essential nutrient that cannot be made in the body, and it is difficult to get significant amounts of vitamin A from food sources.

The purpose of this study is to determine whether taking an oral vitamin A supplement will improve the retinal function of patients with retinitis pigmentosa (RP). Patients with RP progressively lose the ability to read fine print and perceive color.

Fifteen participants age 18 and older who have various types of RP will participate in this study. They will take vitamin A capsules (doses of 15,000 IU to 50,000 UI) daily for 4 weeks; then they will switch to a lower dose for an additional 2 weeks. At an initial visit to the Clinical Center, participants will undergo a medical history, physical exam, blood work, and an eye exam that includes an electroretinogram. During each of five follow-up visits, doctors will measure the amount of vitamin A in participants' blood to see if it increases over time. The follow-up visits will take place approximately every 2 weeks for approximately 2.5 months.

Condition	Treatment or Intervention	Phase
Retinitis Pigmentosa	Drug: Vitamin A	Phase I

Further Study Details: 

Expected Total Enrollment:  6

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, 10-12; sum of thresholds). Safety outcomes include visual fields, ETDRS visual acuity, intraocular pressure, serum vitamin A level and liver function tests.

Genders Eligible for Study:  Both

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.
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. Participants in whom flicker ERG can be measured reliably (standard flicker ERG amplitude greater than 2 mV).
4. Willingness to use contraception for the duration of the study.
5. 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 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 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 mg/dL.

Maryland
      National Eye Institute (NEI), 9000 Rockville Pike,  Bethesda,  Maryland,  20892,  United States

Study ID Numbers:  030255; 03-EI-0255
Record last reviewed:  May 25, 2004
Last Updated:  February 3, 2005
Record first received:  July 23, 2003
ClinicalTrials.gov Identifier:  NCT00065455
Health Authority: United States: Federal Government
ClinicalTrials.gov processed this record on 2005-04-08