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RP Community› RP Articles› Foundation Fighting Blindness : Vitamin A Treatment for RP
| Foundation Fighting Blindness : Vitamin A Treatment for RP |
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| Written by Wiggy | |
| 12 December 2009 | |
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We are pleased to provide the results of a clinical trial that indicate a specified dose of vitamin A can potentially save years of sight for some people with retinitis pigmentosa (RP). Although this is not a cure, it is a first step in managing RP. Equally important, this trial shows it is possible to influence the course of RP. lncluded is a comprehensive list of questions and answers regarding the vitamin A palmitate treatment. This six-year, $5 million study was conducted at the Berman-Gund Laboratory for the Study of Retinal Degenerations of Harvard Medical School with funding by The Foundation Fighting Blindness and National Eye lnstitute, National lnstitutes of Health. Published in the June 1993 issue of Archives of Ophthalmology, the study concludes that most adult patients with RP should take 15,000 lU of vitamin A daily and avoid high doses of vitamin E. However, be sure to consult with your ophthalmologist before beginning this treatment. While vitamin A may help many, it is not a cure. The Foundation Fighting Blindness continues an accelerated research strategy to pursue other treatments -and ultimately, cures -for RP and other retinal degenerative diseases. Sincerely, The Foundation Fighting Blindness Communications Department lnformation & Referral ln 1993, Dr. Eliot Berson and colleagues at The Foundation's Research Center, the Berman-Gund Laboratory for the Study of Retinal Degenerations of Harvard Medical School, published results from a clinical trial, which found that a daily dose of 15,000 lU of vitamin A palmitate on average slowed the course of common forms of retinitis pigmentosa (RP) including Usher syndrome type ll. This clinical trial heralded vitamin A as the first sight-saving treatment for RP. Recently, Dr. Berson and colleagues published results of a 12-year follow-up study evaluating the long-term safety of vitamin A in 146 patients with RP who participated in the original vitamin A clinical trial. These patients were otherwise healthy and between the ages of 18 and 54. The daily doses of vitamin A palmitate for this group of patients ranged between 16,349 lU and 24,918 lU. After 12 years of supplementation, vitamin A blood levels increased by 18 percent. However, all the patients in this follow-up study had blood levels of vitamin A within the normal range. The patients also showed no clinical symptoms or signs of liver toxicity attributable to vitamin A. The study authors conclude, "Prolonged daily consumption of less than 25,000 IU of vitamin A can be considered safe for that time and amount in this age group." While the long-term safety of vitamin A palmitate in healthy adults is now better established, Dr. Berson recommends that before beginning the vitamin A therapy, patients consult their physician to review their medical history and current health status. As a precaution, patients should also have blood tests to measure vitamin A levels and liver function tests prior to beginning the treatment and annually thereafter. lf liver function tests reveal any abnormalities, cessation of vitamin A would be expected to prevent any possible complications due to vitamin A toxicity. This long- term safety study, published in the April 1999 American Journal of Clinical Nutrition, now provides patients and doctors with more complete medical information regarding the safety of the vitamin A treatment for RP. lf you have questions regarding the vitamin A treatment, The Foundation publishes a free booklet entitled, Vitamin A treatment for Retinitis Pigmentosa. The Foundation also distributes a list of mail order companies that provide vitamin A palmitate in 15,000 lU capsules. The Foundation Fighting Blindness 11435 Cronhill Drive Owings Mills, MD 21117-2220 800-683-5555 800-683-5551 (TDD for deaf) 410-568-0150 410-363-7139 (TDD for deaf) www.blindness.org STUDY SHOWS VITAMIN A SLOWS RP Most adults with blinding retinitis pigmentosa (RP) should take a daily 15,000 lU vitamin A palmitate supplement and avoid high dose vitamin E to help prolong their vision, based on results from a large randomized clinical trial published in the June 1993 issue of Archives of Ophthalmology. This recommendation is the first from a well-designed clinical trial indicating that people can be treated for RP. Alan M. Laties, M.D., chairman of The Foundation Fighting Blindness' Scientific Advisory Board, said of these findings, "This treatment can be a benefit, a very real one, for people who have RP. Although not a cure, it will improve quality of life, potentially adding many years of useful vision. The discovery that vitamin E is of no use, and in fact potentially harmful, is not only important on its own, but further justifies this extensive study." Eliot L. Berson, M.D., the study's principal investigator and Professor of Ophthalmology at Harvard Medical School, said that adults who supplemented their diets with 15,000 lU of vitamin A palmitate daily had on average about a 20 percent slower annual decline of remaining retinal function than those not taking this dose. Based on this finding, the investigators estimated that an average patient in the study, who started taking a daily supplement of 15,000 lU vitamin A palmitate at age 32, would retain some useful vision until age 70, whereas a patient not on this dose would lose useful vision by age 63. The investigators also recommended that adults with RP should avoid taking high- dose vitamin E supplements. ln the study, the disease appeared to progress faster on average in patients on a daily 400 lU vitamin E supplement than in those taking a trace amount of the vitamin. However, the study showed no evidence that normal dietary or small supplemental amounts of vitamin E have an adverse effect on the disease. RP is a group of inherited diseases that usually starts with night blindness, followed by progressive loss of peripheral vision. Over a period of years this results in "tunnel vision," and may lead to total blindness. lt causes the progressive deterioration of specialized, light-absorbing cells in the retina, the paper-thin tissue that lines the back of the eye like film in a camera. The majority of people with RP are legally blind by the age of 40, with a central visual field of less than 20 degrees in diameter. An estimated 1.5 million people worldwide are affected by RP. The carefully designed and monitored clinical trial involved 600 patients with RP between the ages of 18 and 49, who were at different levels of visual function. The six-year study was conducted at a cost of $5 million at the Berman-Gund Laboratory for the Study of Retinal Degenerations at Harvard Medical School, with the support of The National Eye lnstitute and The Foundation Fighting Blindness. The investigators stressed that adults considering vitamin A palmitate supplementation should first: * Consult with their doctor about vitamin A palmitate supplementation. * Have fasting blood levels of vitamin A measured and liver function tests administered before starting treatment. People with certain preexisting medical conditions may not be eligible for this treatment. * Take vitamin A palmitate, since this form of the vitamin was used in the study. Beta-carotene, a natural precursor of vitamin A, is not a predictable source of vitamin A and therefore is not a suitable substitute for vitamin A palmitate. * Make a point of eating a balanced diet, without selecting foods that are especially high in vitamin A. * Avoid taking high-dose vitamin E supplements. Commenting on the results of the vitamin A study, Dr. Berson stated, "One of my biggest concerns is that people will make the mistake of thinking that vitamin A supplementation in excess of the 15,000 lU recommended will provide even greater benefit. We have evidence in fact that supplementation of a regular diet with greater than 15,000 lU of vitamin A does not provide greater benefit. Moreover, a daily vitamin A intake exceeding 25,000 lU over the long-term can be toxic in adults and may cause side effects such as liver disease' "Our interpretation of the study results is that the course of the common forms of retinitis pigmentosa is slower on average among adult patients on a regular diet who take a daily 15,000 lU vitamin A supplement in the palmitate form compared with the course of those patients not on this supplement." Because the study involved adults between the ages of 18 and 49, no formal recommendations can be made for patients under the age of 18. Also, women with RP should not take 15,000 lU vitamin A palmitate supplements during the time leading up to planned pregnancy and during pregnancy, because high doses of vitamin A have been linked to birth defects. Questions and Answers About Vitamin A Palmitate Supplementation as a Long-Term Treatment for RP 1. ls this a treatment for RP? Based on the results of a six-year study of 600 patients with typical retinitis pigmentosa (RP), researchers concluded that, on average, the course of retinal degeneration was slower among patients receiving a daily vitamin A palmitate supplement (15,000 lU) than was the disease course among those not taking this dosage. There was about a 20 percent slower rate of decline of remaining retinal function (8.3 percent) per year in the 15,000 lU dose group versus the control (trace dose) group (10.0 percent), as monitored by electroretinographic (ERG) amplitudes. The results also suggested that the course of disease mignt be faster on average among patients receiving a daily high dose supplement of vitamin E (400 lU) than among those receiving a trace dose of vitamin E. lt is recommended that most adult patients with the common forms of RP take a daily 15,000 lU supplement of vitamin A palmitate under the supervision of a doctor and avoid the use of high dose supplements of vitamin E, such as 400 lU. 2. ls this a cure? This treatment may decrease the total loss of vision over a lifetime and thereby delay blindness. Adults who use this treatment have on average about a 20 percent slower annual decline of remaining retinal function than those not using this treatment. While this does not represent a cure, it does represent a first step in treating typical RP. The patient must realize that this study did not find improved vision from one year to the next, and did not find that vision loss was completely arrested. Research aimed toward the development of additional treatments, a cure, and prevention actively continues. 3. What types of RP may be helped by this treatment? The clinical treatment trial of vitamin supplementation studied patients with typical forms of RP, including the inheritance types of X-linked, autosomal dominant, and autosomal recessive, as well as isolated RP and Usher syndrome type ll. Several other forms of RP were not included in the study because there was no preliminary evidence to suggest that vitamins could modify the course of these forms. Diseases not included in this study were Usher syndrome type l, sector RP, cone-rod dystrophy, unilateral RP, Bardet-Biedl syndrome, choroideremia, gyrate atrophy, Leber congenital amaurosis, Refsum disease, and other less common syndromes that involve RP. Also, patients were not evaluated in this study if they had very advanced RP (less than 8 degree visual field with a large test light; if they were below the fifth percentile of normal with respect to body weight for a given age, sex, and height; if they had impaired liver function; or if they were under age 18. Therefore, formal recommendation with respect to vitamin A palmitate supplementation cannot be made for these groups of patients. They should be assessed individually by their doctors. 4. Was any type of macular degeneration included in this study? No. This study was limited only to typical RP. Macular degeneration, whether the juvenile onset or late onset age-related forms, was not included in this trial. ln fact, because macular degeneration has different symptoms than RP, it might also be caused by different disease processes than RP. Recommendations regarding vitamin supplementation for patients with macular degeneration will have to await completion of other studies now being conducted through other large multi-center projects supported by the US government. 5. Can children who have RP be given supplements of vitamin A palmitate? Because patients under the age of 18 were not evaluated in this study, no formal recommendation can be made. Patients under 18 years of age should consult with their ophthalmologist and pediatrician for possible vitamin A palmitate treatment with a dose that takes into account the age, weight, general health status, and published guidelines for the safe use of vitamin A palmitate. A 15,000 lU daily supplement of vitamin A is well above a child's recommended daily allowance and could be toxic. Your child's doctor might recommend that your child take a daily multiple vitamin capsule that contains the recommended daily allowance for children. 6. Tell me more about this study on vitamin A. Why was it done? This study was a prospective, double-masked clinical trial, meaning neither patient nor clinician knew to which treatment group the patient had been randomly assigned. lt was designed to assess the effectiveness of vitamin A and E supplements in halting or slowing the progression of RP. An independent data and safety monitoring committee provided advice to the investigators and monitored the accumulating data on a regular basis for evidence of harm or benefit to study participants. A total of 600 patients affected with typical RP from across the United States and Canada were enrolled in the study. All were in good general health, between the ages of 18 and 49, and entered the study with different levels of retinal function. Following an examination, participants were assigned randomly to one of four treatment groups: 1) 15,000 lU vitamin A plus 3lU vitamin E 2) 75 lU vitamin A Plus 3 lU vitamin E 3) 15,000 lU vitamin A plus 400 lU vitamin E 4) 75 lU vitamin A plus 400 lU vitamin E Thereafter, the researchers examined each patient annually, with an average follow-up of 5.2 years. The electroretinogram (ERG) was used as the primary measure to follow the course of the disease. The ERG is a light-evoked electrical response from the retina that can be accurately measured. Much like an electrocardiogram measures heart function, an ERG provides an objective measure of retinal funition. 7. where can I get a copy of the full report on this study? The report from this clinical treatment trial was published in the June l993 issue of the medical science journal Archives of Ophthalmology, pages 761-772. You and your doctor should refer to this article for a complete presentation and discussion of the results. This journal is available through medical school and university libraries. Your local library may be able to obtain a copy of the article for you. An abridged version of this study is reprinted in the back of this booklet. 8. Do the results of this study imply that vitamin A deficiency or an excess of vitamin E was the cause of my RP? No, vitamin A and E levels present in the blood of unaffected and affected individuals do not differ significantly. Scientists have discovered that the actual cause of most typical RP is a mutation in one of several important genes, which then produces a defective protein in photoreceptor cells (rods and cones). lt is well known that vitamin A is critical to normal retinal function. However, the precise benefit vitamin A provides is unknown. 9. What is vitamin A? Vitamins are relatively complex organic substances that are not made by the human body. They are required in small amounts from a balanced diet in order to sustain normal metabolism and good health. Diseases caused by extreme vitamin deficiency can usually be cured when the lacking vitamin is supplied. Vitamin A is essential to normal cell growth and development. lt plays an important role in visual function. Severe nutritional deficiency of vitamin A can cause disease (especially of the eye) and degeneration of mucous membranes. 10. How does supplemental vitamin A palmitate preserve vision for RP patients? We don't know the answer to that question yet. One well-defined function of vitamin A is in vision. lt is intimately involved in the cascade of events triggered by light reaching the retina and culminating in delivery of an image to the brain. A second major role of vitamin A is during the developmental stages of life when simple cells change into specific types of cells like those in the retina. A characteristic of the typical forms of RP is death of the specific, light-sensing cells in the retina, the photoreceptor cells called rods and cones. lt is reasonable to hypothesize that high levels of vitamin A preserve these dying cells in some way. lt is also possible that some patients with RP have a reduced capacity to retain vitamin A in the retina due to the condition of the sick, degenerating rods and cones. Likewise, such cells may have an abnormal carrier protein causing vitamin A to be transported from the blood to the retina with lower efficiency. Whatever the explanation, it appears that vitamin A supplements may provide partial protection against cell degeneration. Research will continue to seek an understanding of this effect, with the hope of further enhancing its positive actions. 11. Why should I avoid high dose supplements of vitamin E? On average, study patients who took 400 lU of vitamin E daily as a supplement appeared to experience close to a 20 percent faster rate of visual function decline per year than those who received only a trace amount of vitamin E (11.8 percent compared to 10.0 percent). ln other words, the average patient taking 400 lU of vitamin E could expect to lose visual function several years sooner. lf vitamin E supplements, without vitamin A, were started by the average patient at age 32, legal blindness would be accelerated by as much as five years. However, the study found no evidence that normal dietary or small supplemental amounts of vitamin E have an adverse effect on RP. 12. How could vitamin E cause a negative effect on RP? It is possible that a daily high dose of vitamin E might affect the course of RP at least in part by inhibiting the absorption or transport of vitamin A. ln the study, it was observed that patients receiving 400 lU vitamin E had slight but significant decreases in blood vitamin A concentration compared with those not receiving that dose of vitamin E. 13. What if my doctor advised me to take vitamin E for other reasons? There is some early information from nutritional studies suggesting that supplemental vitamin E could be helpful in preventing heart disease. lf your doctor has advised you to take vitamin E for that reason, you should ask to discuss the relative benefits and risks of taking vitamin E, or taking vitamin E along with vitamin A, given your general health and your eye disease. 14. What is the benefit of vitamin A palmitate for the "average" individual who has RP or Usher syndrome type ll? ln this clinical treatment trial, patients were examined annually for four to six years. Visual function was assessed by an ERG (electroretinogram). Those who took daily vitamin A supplements of 15,000 lU had close to 20 percent slower loss of remaining visual function each year than others in the study. lf the average patient started vitamin A supplements at age 32, legal blindness could be delayed by as much as seven years. However, researchers cannot provide assurance that every patient will benefit from treatment with vitamin A palmitate. 15. To what extent might my vision be saved? Because the results of this study are based on group averages, individual outcomes cannot be predicted. There are considerable differences in the severity of the disease among individuals at the same age, even within the same family. This study pooled the information from 600 patients and conclusions were based on "group averages." Actually, there are probably very few patients who exactly fit the "average" description. Some will have better vision and some will have worse vision than the average study patient. lt isn't possible to tell you the exact extent of benefit you will receive from this treatment. Some patients may not be helped at all; some may be helped more than others. 16. But what does that say about me? The best we can answer is that you may have a high likelihood of benefiting from vitamin A treatment. This treatment slows the rate of a degenerative process, but does not stop it. For some patients it may prevent total blindness, while others may not be helped at all. 17. Will I notice any change in my vision when l take vitamin A? It is very unlikely that you will notice an improvement in your vision compared to any time in the past. The degenerative process will continue, although at a slower rate. Based on the results of this study, it is predicted that patients taking vitamin A over the long-term would have a higher probability of retaining the capacity to perform certain daily activities at a given age than patients not taking the vitamin A treatment. 18. lf I take vitamin A long enough, or start taking vitamin A as a young adult, will I be cured? Vitamin A supplementation is not a cure for RP. "Cure" implies that health has been restored to normal, and a cure for RP would imply restoration of lost vision. Vitamin A supplementation does slow the rate of visual function loss, therefore it is expected that supplementation begun in early adulthood may be more beneficial in the iong- term than if begun later. For some patients, this might result in some amount of retained central vision for life. 19. Should l take vitamin A if l am already legally blind? This study did not evaluate patients with extremely low-vision because ongoing measurements of change in vision would have been difficult to assess in those patients. lf you now have very advanced RP, you should consult with your ophthalmologist for advice about the possible benefit of vitamin A for you. 20. What should I do to begin vitamin A treatment? Consult with an ophthalmologist, a medical doctor who specializes in eye care. Do not start taking vitamin A supplements on your own. Your ophthalmologist will want to administer blood tests to measure your fasting blood levels of vitamin A and to assess your liver function. Other standard laboratory tests may also be done before starting your treatment. These tests are needed to assure that you do not have a pre-existing medical condition that would prevent you from taking this treatment. lf blood tests indicate you already have abnormally high levels of vitamin A, your doctor may need to adjust your vitamin A intake accordingly. lf you are not going to an ophthalmologist now, we recommend that you find one who is willing to advise you regarding your eye care. 21. How often will I need to be examined while taking vitamin A? It would be a good practice to visit your doctor annually. Annual blood tests to measure fasting levels of vitamin A will help to insure your are receiving the appropriate intake of vitamin A as required by the study over the long-term. Liver toxicity is a potential complication of daily doses of vitamin A in excess of 25,000 lU, so blood tests to reassess liver function should be done annually. As reported in the study, no significant chronic or acute toxicity of any kind was found in the groups taking vitamin A. Surveys of the medical literature find no reported toxicity among patients in good general health who are taking daily doses of 15,000 lU of vitamin A. 22. Is it safe to take 15,000 lU of vitamin A for many years? No evidence of systemic illness or toxicity attributable to the daily intake of vitamin A palmitate capsules (15,000 lU) used in the clinical treatment trial could be established during the six-year study based on blood tests, urinalyses, patient responses to a symptom questionnaire, and, in some cases, examination by a consulting internist. Nevertheless, it is extremely important that your own condition be monitored by a physician on a regular basis while you are taking vitamin A for extended time periods that will probably exceed the six year term of this study. We cannot exclude the possibility of the development of side effects. Therefore, to monitor treatment, we recommend that patients have a yearly evaluation by their doctor. 23. What are the possible side effects of taking too much vitamin A? For normal, healthy adults the US Recommended Daily Allowance (US RDA) for vitamin A is 5,000 IU. The recommended daily dose for most adult patients with RP is 15,000 lU from capsule supplements, in addition to a regular balanced diet, which typically provides 3,000-4,000 lU per day. This totals approximately 18,500 lU per day of vitamin A. Regular long-term intake in excess of 25,000 lU has been associated with liver toxicity. Side effects and complications from very high doses include liver toxicity, persistent headache, joint or bone pain, appetite loss, weight loss, nausea, vomiting, unusually dry skin, increased hair loss, and fatigue. When taken during pregnancy, high-dose vitamin A has also been associated with birth defects. 24. Should I be concerned with alcohol consumption while taking vitamin A? It is well known that excessive alcohol consumption can cause liver toxicity. However, no systematic studies have been done in patients taking 15,000 lU of vitamin A to see if excessive alcohol consumption would be more likely to produce liver toxicity. lt is therefore advisable to limit alcohol consumption to no more than two drinks per day (one drink is equivalent to 12 oz. beer, 4 oz. of wine, or 1 ounce of hard liquor). 25. What about cigarette smoking and vitamin A? A recent study found that current and former heavy smokers (i.e., two packs a day for 25 years) who took 25,000 lU of vitamin A and 30 mg of beta-carotene had 28 percent more lung cancers and 17 percent more deaths than those current and former heavy smokers who did not take these supplements. This percentage increase in lung cancers is equivalent to 2 additional cases per year for every 1000 smokers. During the 4 to 6 year course of the vitamin A clinical trial for RP, there were no reported cases of lung cancer among study subjects who took 15,000 lU of vitamin A. lf you are a current or former heavy smoker, please share your smoking history with your physician. lt should be stressed that there are no reports in the medical literature of vitamin A increasing the risk of lung cancer in non-smokers. 26. Should I continue this treatment if I become pregnant or plan to become pregnant? Women who are pregnant or are planning to become pregnant should not take high doses of vitamin A because of the potential for birth defects. Women should discuss the impact of vitamin A treatment on childbearing with their doctor. You should stop taking vitamin A before a planned pregnancy. Women who become pregnant should immediately discontinue this dose of vitamin A palmitate during the entire pregnancy. However, you should take prenatal vitamins as prescribed by your obstetrician. Patients should consult with their doctor about taking this dose while breast-feeding. 27. If l'm planning to become pregnant, when should lstop taking vitamin A? There is no scientific data to tell us when you should stop, but if you are planning to become pregnant, you should discontinue this regimen. 28. How can I find a doctor who is familiar with RP? The Foundation Fighting Blindness sponsors 18 Research Centers, many of which are in the US and can provide access to ophthalmologists who specialize in retinal degenerative diseases. The Foundation also offers a nationwide list of retinal specialists to help individuals who are outside the geographic range of The Foundation's Research Centers. This referral list was compiled by contacting all vitreo-retinal specialists who are members of the American Academy of Ophthalmology. All those listed indicated interest in seeing individuals with inherited retinal degenerative diseases. Please be aware that The Foundation has not screened these ophthalmologists to judge their training, experience or standing in the medical community and cannot recommend one in preference to another. Also, The Foundation cannot be held responsible for any services given by referral specialists or for the fees that they may charge. ln conjunction with this list, you may wish to consult with your general ophthalmologist, optometrist or family doctor for his or her recommendation. You may also wish to consult with your state department of rehabilitation, local medical society, university medical school, or major hospital ophthalmology clinic for a referral to a retinal specialist. 29. Will my health insurance pay for annual appointments and tests? You will need to check with your individual health insurance carrier. Coverage of costs will depend on the individual insurance plan being used. Medicaid and Medicare coverage might be available, but will probably vary from state to state. When checking with your health insurance carrier, you should indicate that you are receiving treatment based on the results of a clinical trial endorsed by the National Eye lnstitute. 30. What do I need to know in order to buy the right capsules of vitamin A? For normal healthy adults the US RDA of vitamin A is 5,000 lU, while the recommended daily dose based on the results of this clinical treatment trial is 15,000 lU vitamin A palmitate per day for most adults with RP. The designation "lU" stands for lnternational Unit. "lU" is a standardized measurement that quantifies the amount of the specific substance present in the capsule. When you look for such a supplement, labels should be read very carefully to be sure the capsules contain vitamin A palmitate, and not another component like beta-carotene. Beta-carotene is a natural precursor of the active form of vitamin A. Very high levels of beta-carotene are needed to achieve activity equivalent to 15,000 lU of vitamin A palmitate. The final activity could vary from person to person because people metabolize beta- carotene with different efficiencies. Therefore, beta-carotene is not a predictable source of the vitamin and is not recommended in context to this study. Vitamin A in the palmitate form was used in this clinical treatment trial and the recommendations derived from the study apply specifically to this form. 31. Do I need a prescription to get vitamin A supplements? No. 32. where can l obtain capsules of 15,000 lU vitamin A palmitate? The Foundation keeps an updated list of vitamin A palmitate suppliers. 33' Why can't I simply take three "one-a-day" multiple vitamin capsules each day? Wouldn't I get the right dosage of vitamin A? Because these capsules contain many vitamins and other components at 100 percent of the US RDA, three one-a-day multiple vitamin capsules a day are not recommended. ln addition, each of these multiple vitamins includes the US RDA of vitamin E, which appears to interfere with the beneficial action of vitamin A for RP taken in high doses. 34. Can I adiust my daily dose so that I can make use of the vitamin A capsules of lower or higher dosages that are sold at my local stores? At present in the US, locally available preparations of vitamin A are provided in 10,000 lU and 25,000 lU capsules as either a water soluble base, in the acetate form, or concentrated from fish liver oil. These vitamins cannot be recommended because they were not part of the study, do not contain the appropriate dosage and may not contain the vitamin in the palmitate form. ln the study, optimal benefit occurred among patients with a total daily intake of 15'000 lU of vitamin A palmitate in capsule form and 3,000 lU vitamin A from diet. Lower intake gave less benefit and higher intake up to 25,000 lU provided no greater benefit. Toxic side effects have been associated with long-term intake of 25,000 lU and therefore, capsules of 25,000 lU should be avoided. Combinations to achieve an average of 15,000 lU per day over several days (for example, 3 capsules of 10,000 lU every two days) are not recommended because it would be hard to take three capsules evenly spaced over a two day period and you could risk temporarily high blood levels of the vitamin. Remember, more vitamin A than the recommended dose is not better. Moreover, daily vitamin A intake exceeding 25,000 lU over the long-term may be toxic in adults and may cause side effects such as liver disease. 35. when should I take the capsules and how should I store them? You might find it useful to develop a routine of taking one capsule each day right after breakfast. These vitamin A capsules have more than a one-year sheli life. On the advice of your doctor, you could order a full year supply (four-bottles of 100 each) and store them at room temperature. Keep capsules out of the reach of children. 36. Should I be concerned about getting the right amounts of vitamin A and vitamin E in my diet? The average American diet provides approximately 3,000-4,000 lU of vitamin A per day. ln the clinical treatment trial, the actual average intake for the patients was 3,OOO lU per day. This daily dietary amount was taken into account for the final recommendation of a supplement of 15,000 lU vitamin A palmitate per day as a treatment for RP. You should maintain a regular, balanced diet, following the standard guidelines for good nutrition developed by the US Department of Agriculture (USDA). You should NOT try to specifically select foods that are high in vitamin A content. Also, you should NOT try to eliminate foods that are high in vitamin E content. 37. ls there anything else I can do besides maintaining a balanced diet and taking vitamin A to preserve my vision? At this time, no other approaches for preserving vision affected by RP have been proven useful and safe through a carefully controlled clinical treatment trial. Some doctors advise their patients io protect their eyes from bright light. As a precaution, individuals with RP are encouraged to protect their eyes from long-term exposure to bright sunlight until more is learned. Good quality sunglasses are useful for bright days outdoors. 38. Should I be encouraged by the discovery of this treatment? This breakthrough is a concrete reward for the many years of research that preceded it. Daily vitamin A supptementation is the first discovered means to partially control RP that has proven useful and safe for most patients. This clinical treatment trial has demonstrated that ways to slow vision loss can be proposed and tested, and is an extraordinary example of carefully designed work. lt was done under close monitoring for appropriate benefit and avoidance of risk to patients. lt will serve as a model for future studies. Meanwhile, until a cure is found, some years of vision may be saved for some patients affected with RP' 39. Will other research on RP stop now that this treatment has been found? No. This treatment may preserve visual function in certain patients with RP while the search for additional ahd improved treatments and the means to cure or prevent RP continues. Studies on nutritional supplements represent only one aspect of the overall scientific strategy. Currently, funding is provided by The Foundation for over 100 research projects done at 13 dedicated RP Research Centers and other universities and research institutions worldwide. The National Eye lnstitute devotes additional federal funds to this topic. This disease must be understood at the most basic cellular level in order to understand how it is caused and how it can be stopped. Research in biochemistry and cell biology, as well as molecular genetics and clinical studies, will lead to the design and testing of other treatments that may stop the progression of the disease and ultimately prevent it from ever occurring. 40. Can I volunteer to participate in a ctinical treatment trial in the future? The Foundation maintains a computerized National Registry to identify and collect medical and family histories on all people in the US with retinal degenerative diseases. Participants who complete a Registry questionnaire may give permission to The Foundation to release their names to researchers for Foundation-approved studies. Many patients asked to participate in future clinical studies will be identified through the National Registry. Registry forms are available through The Foundation. ln addition, patients seen regularly at a Foundation Research Center may be included in certain clinical studies at that center. Disclaimer Retinal degenerations are very difficult diseases to describe because each case is so different. That,is why the information presented in this booklet is offered only as general information and as referral to other sources for complete information. lf you suspect you have retinal degeneration, or any other eye problem, it is best to consult with an ophthalmologist, a physician who specializes in the care of the eye. lf you think long-term treatment with 15,000 lU vitamin A palmitate may apply to your condition, you should consult with an ophthalmologist before taking such high dose supplements. The Foundation Fighting Blindness can not be held responsible for any individual's decisions or actions regarding eye health care. Vilamin A Supplementation for Retinitis Pigmenosa Eliot L. Berson, M.D. Summary of paprer published in Archives of Ophthalmology, June 1993 Page I of 3 Randomized Trial of Vitamin A and Vitamin E Supplementation for Retinitis Pigmentosa Study Design Randomizcd, controlled, double-masked tial 601 adult Patients, ages 18-49 Facorial desisn -four treatment groups: 15,000 IU of A + 3 IU of E (Group A) 75 IU of A + 3 IU of E (Group Trace) 15,000 IU of A + 400 IU of E (Group A+E) 400 IU of E + 75 IU of A (Group E) Mean outcome variable: 30Hz Cone ERG Two pre-treatment examinations at 6-week interval: Screening to establish eligibility; baseline to determine intervisit variability Average of screening and baseline visits to provide pretreatment values Groups balanced with respect to genetic type and pretreatment intake of A and E Annual follow-up: ERGs,visual fields,visual acuities Compliance: serum, capsule counts, calendars Outside Data safety and Monitoring Committee appointed by the National Eye Institute EligibilityCriteria Common forms of retinitis pigmentosa; ages 18-49; one/family Visual Acuity >20/100; visual field 28o diameter to V4e, white test light 30 Hz ERG>0.12microvolt or 0.5 Hz ERG > 2.5microvolt (Norms: 30Hz>50microvolt; 0.5Hz > 350microvolt) Total intake: vitamin A <11,500IU/day; vitamin E<40IU/day Normal serum retinol (<l00micrograms/dL); normal serum liver function profile Not pregnant or planning to become pregnant Weight above lower fifth percentile for age, sex, and height Agree not to know content of supplepent or group assignment Masking All members of the staff in contact with the patients were masked as to the treatment group assignmcnt of each Patient Each ocular examination and ERG was performed without review of previous records All serum samples were analyzed without knowledge of treatment group assignment Patients did not know the contents of the supplement or their goup assignment Patients agreed not to know the course of their retinal degeneration until the end of the study |
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