Herbal, Nutritional Supplements Linked to Ocular Side Effects
Key points
- An estimated 42 percent of Americans use herbal medicines or nutritional supplements.
- Fraunfelder, M.D., assistant professor of ophthalmology in the OHSU School of Medicine and the OHSU Casey Eye Institute, found side effects ranging from dry eye to retinal hemorrhages and transient visual loss.
- Most of the side effects were associated with higher doses and topical application.
- "A large segment of the population uses herbal medicines and nutritional supplements, many times without the treating physician's knowledge," said Fraunfelder, who also is director of the National Registry of Drug-Induced Ocular Side Effects based at the Casey Eye Institute.
An estimated 42 percent of Americans use herbal medicines or nutritional supplements. Many people taking these products and their physicians are unaware of the adverse reactions they can cause. An Oregon Health & Science University researcher reviewed reported cases of ocular side effects associated with these products. His findings are published in the American Journal of Ophthalmology this month.
The researcher, Frederick W. Fraunfelder, M.D., assistant professor of ophthalmology in the OHSU School of Medicine and the OHSU Casey Eye Institute, found side effects ranging from dry eye to retinal hemorrhages and transient visual loss.
Most of the side effects were associated with higher doses and topical application. While none of the reported cases caused permanent damage, many could have if the patient had not discontinued use of the product.
"A large segment of the population uses herbal medicines and nutritional supplements, many times without the treating physician's knowledge," said Fraunfelder, who also is director of the National Registry of Drug-Induced Ocular Side Effects based at the Casey Eye Institute. "These products can cause ocular side effects and clinicians need to recognize these adverse events."
Herbal medicines and nutritional supplements are not regulated by the Food and Drug Administration (FDA) as prescription and over-the-counter medications are. The World Health Organization (WHO) published guidelines on the use of herbal medicines in 2004, including recommendations on cultivating, collecting, classification, quality control, storage, labeling and distribution. However, there are no official standards governing the production of herbal medicines in the United States and the potency and purity of these products vary widely.
Fraunfelder reviewed cases of adverse ocular side effects reported to the WHO, the FDA and the National Registry of Drug-Induced Ocular Side Effects, and reviewed world literature for reported instances of adverse ocular side effects caused by herbal medicines and nutritional supplements. Out of 323 reported cases he found eight products associated with clinically significant ocular side effects: ginkgo biloba, Echinacea purpurea, chamomile, licorice, canthaxanthine, Datura, niacin and vitamin A.
One of the best-selling herbal medicines in the United States and worldwide is ginkgo biloba, which is used to treat tinnitus, asthma and tonsillitis among other things. Fraunfelder found two cases of hemorrhaging in the anterior chamber of the eye as well as reports of retinal hemorrhages in patients taking this agent. Ginkgo biloba inhibits platelet aggregation, and should be used with caution in patients taking aspirin because the effects could be amplified. Echinacea purpurea is used to treat colds, coughs, fevers, urinary tract infections, burns and influenza. Reports of eye irritation and conjunctivitis have been associated with its topical use.
Written and revised by
Gerald Hurowitz, M.D.
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