Table of Contents
FDA Consumer magazine
July-August 2000
The first in a new class of antibacterial drugs to treat serious infections resistant to other antibiotics has been approved by the Food and Drug Administration. Zyvox (linezolid) was approved April 18, less than a month after an FDA advisory committee reviewed study data and recommended its approval.
Zyvox treats infections, including bloodstream infections, associated with vancomycin-resistant Enterococcus faecium (VREF). Vancomycin has long been the drug of last resort in treating infections resistant to other antibiotics. Zyvox also was approved for the treatment of hospital-acquired pneumonia and complicated skin infections, including those due to methicillin-resistant Staphylococcus aureus (MRSA), for community-acquired pneumonia and for uncomplicated skin and skin structure infections.
Infections due to Enterococcus faecium and MRSA are a particular problem in hospital patients and in people with compromised immunity, such as people with AIDS or cancer. The first case of VREF was reported in this country in 1989. Since then, there has been a rapid increase in the incidence of VREF infections, as well as a dramatic rise in the incidence of MRSA infections.
Last fall, FDA approved Synercid, a combination of two older antibiotics, to treat infections resistant to vancomycin. Zyvox, however, is the first in a new class of synthetic drugs--the oxazolidinone class--approved for use in the United States and the world. It is also the first drug in over 40 years to be introduced into the U.S. market for treatment of MRSA infections.
The most frequently reported side effects attributed to Zyvox in clinical studies were headache, nausea, diarrhea, and vomiting. The most important laboratory test change was a decrease in platelet counts.
Zyvox may interact with certain other drugs, including over-the-counter cold remedies that contain pseudoephedrine or phenylpropanolamine, causing an increase in blood pressure. Patients receiving Zyvox should tell their doctors if they are taking such medications.
Therapy with Zyvox is expected to first take place mainly in hospitals or other institutional settings. Doctors have been advised to consider alternatives before prescribing Zyvox to outpatients, due to concerns about inappropriate use of antibiotics leading to an increase in resistant organisms.
Pharmacia and Upjohn, based in Kalamazoo, Mich., developed Zyvox and will market it in the United States.
A remarkable new Star Wars-like therapy that uses laser light to activate a drug within the blood vessels of diseased eyes has provided the first effective therapy for "wet age-related macular degeneration" (AMD). In April, the Food and Drug Administration approved Visudyne (verteporfin for injection) for treatment of the classic type of wet AMD. AMD is a form of degenerative nerve disease that destroys the eye's retina, causing severe and irreversible vision loss. It is a major cause of blindness in people over 60 years old in the Western World. While 90 percent of AMD is the "dry" form and only 10 percent is the "wet" form, the "wet" form destroys vision more quickly.
Wet AMD is caused by the growth of abnormal leaky blood vessels in the eye. The leaking blood eventually damages the macula--the area of the eye's retina responsible for central vision. Central vision is essential for most visual activities, including reading, driving, and recognizing faces.
With AMD, the central field of vision is affected in varying degrees, while peripheral or side vision remains unaffected. Untreated, the majority of eyes with wet AMD will become functionally blind within two years. Visudyne therapy slows damage to the retina, but does not restore vision in eyes that have been damaged by AMD.
Visudyne therapy is relatively painless, takes about 20 minutes, and can be performed in a doctor's office. First, Visudyne is injected intravenously into the patient's arm. The drug travels through the body to the abnormal vessels in the eye. Next, the drug is activated by shining a laser light into the patient's eye for about 90 seconds. The laser changes the drug's molecular shape in such a way that the drug stops or slows blood leakage from the vessel, at least temporarily, slowing the rate of vision decline. Patients should be re-examined every three months to check for new leaks; if they occur, the treatment must be repeated. Because light activates the drug, the patient must avoid exposing skin or eyes to direct sunlight or bright indoor light for five days after treatment.
Fewer than 2 percent of the patients in clinical trials stopped therapy due to side effects. Unfortunately, within seven days of treatment, 1 to 4 percent of patients experienced a severe vision decrease equivalent to the loss of four or more lines of vision on a standard eye chart. The most common side effects included reactions at the injection site, passing vision disturbances, and increased sensitivity to light.
Visudyne therapy is manufactured by QLT PhotoTherapeutics Inc., the eye care unit of Novartis AG, and is marketed worldwide by CIBA Vision.
Routine dental x-rays may be an early-warning system for the risk of dying from a heart attack or stroke, according to research conducted at the University of Buffalo. Researchers found that individuals with calcified plaque in their carotid arteries were twice as likely to die from heart attack or stroke as those with no plaque. The carotid arteries are large vessels on either side of the neck that carry blood from the heart to the brain. Plaque in these arteries, which can be seen on standard panoramic dental x-rays, increases the chances of the vessels narrowing or clots forming. Study results were reported on April 4 at the annual meeting of the International Association for Dental Research.
Antiseptic sterile skin products manufactured by Clinipad Corp. of Rocky Hill, Conn., were voluntarily recalled by the company in March because they could be contaminated by bacteria that cause serious--even life-threatening--skin, wound, or other infections. The products are frequently used at blood collection centers.
There have been no known instances of blood contamination traceable to the recalled products; however, the company confirmed bacterial contamination in some lots of its sterile products, one of which was recalled in December 1999, and could not assure the sterility of other products labeled and sold as sterile.
The swabsticks, prep pads, towelettes, ointments, pouches, and dressings are distributed under the tradenames Cliniswab, Clinipad, Clinidine, Cliniguard, EZ Prep, Cooper Instrument Corp., Moore Medical Corp., and Rauscher. Sold separately or packed in kits, they were distributed to blood banks, hospitals, clinics and retail pharmacies. Products in the recall were manufactured from January 1, 1997, to the time of the recall and include povidone iodine, tincture of iodine, benzoin tincture, acetone alcohol, and alcohol antiseptic products as well as Sterile Cliniguard Protective Dressing.
Products in the recall are labeled "sterile" or "sterile unless opened or damaged." They have lot numbers beginning with 7,8,9, or 0. Health professionals and consumers who have products with these lot numbers should destroy them.
Consumers and health professionals can get more information about the recall on the World Wide Web at www.fda.gov/medwatch/. To help blood collection centers develop alternative skin preparations, FDA has also posted information on www.fda.gov/cber/infosheets.htm and www.fda.gov/cber/recalls.htm.
Clinipad Corp. has sent recall notices to 3,000 customers and 100 kit manufacturers. Consumers with questions may contact the Clinipad Corporation at 860-571-0100.
The burning, bubbling, boiling sensation can last for minutes, hours, even days. It's often worse after eating. You can feel it, the sensation of stomach acid eating away at the esophagus. Heartburn. The American College of Gastroenterology estimates that more than 60 million Americans suffer heartburn at least once a month, and that more than 15 million Americans have the symptoms every day. If the heartburn is severe, or if it happens at least twice a week, you may have Gastroesophageal Reflux Disease, or GERD, a serious disorder that can lead to esophageal cancer.
Scientists believe GERD develops when the muscular valve at the lower end of the esophagus, where it connects to the stomach, malfunctions. The muscle relaxes too often and too easily, allowing stomach acid to flow up into the esophagus. Typically, GERD is treated with behavior modifications such as weight loss and dietary changes, antacids and other medications, and surgery.
But now, sufferers have available an entirely new approach. In April the Food and Drug Administration cleared for marketing two new medical devices that promise to control many of the symptoms related to gastric reflux. The devices, the Stretta System by Conway Stuart (now called "Curon") and the Bard Endoscopic Suturing System (BESS), provide potential alternatives to drugs and more invasive surgery for GERD by fixing the loosened muscle valve. Both use an endoscope, a tube with a built-in camera, inserted through the throat to provide the specific therapy to the area that joins the esophagus to the stomach. The two devices tighten the valve in different ways.
The Stretta System uses a radio frequency energy generator to heat the tissue, shrinking the valve opening. The manufacturer, Curon, markets similar devices for tissue coagulation to treat snoring.
The BESS places small sutures, or "stitches," in the soft tissues of the esophagus and stomach. This tightens the valve, preventing stomach contents from flowing up into the esophagus.
Both procedures can be performed on an outpatient basis because they require no incisions and usually no general anesthesia. It's not known how long the benefits of treatment will last with either device, says Brian E. Harvey, M.D., the senior medical officer in FDA's Center for Devices and Radiological Health who reviewed the two device applications. Patients may need to be retreated if the acid reflux symptoms return.
The Bard Endoscopic Suturing System is manufactured by C.R. Bard, Inc., of Murray Hill, N.J. The SDM Stretta System is manufactured by Curon Medical, Inc., of Sunnyvale, Calif.
A new medical device to treat female sexual arousal disorder (FSAD) has been cleared for marketing by the Food and Drug Administration. Available by prescription only, the Eros Clitoral Therapy Device consists of a small, soft, plastic vacuum cup attached by a tube to a palm-sized battery-operated vacuum pump. The cup is placed over the clitoris prior to sex and the pump draws blood into the clitoris through gentle suction, causing engorgement, which aids sexual arousal.
The device's effectiveness was studied in 25 women, 15 of whom had FSAD. Each of the women used the device during six sexual encounters. Of the 15 women with FSAD, all experienced more sensation; seven, more orgasm; 12, more satisfaction; and 11, more lubrication. Of the 10 women without FSAD, four experienced more sensation; four, more orgasm; two, more satisfaction; and three, more lubrication.
No adverse events from using the device were reported.
FSAD is a persistent or recurrent inability to attain or maintain adequate vaginal lubrication, expansion of the vagina and swelling of the external genitalia during sexual activity.
The Eros Clitoral Therapy Device is manufactured by UroMetrics, Inc., of St. Paul, Minn.
Foods developed using genetic engineering will be subject to mandatory oversight before they reach the market, according to plans announced by the Food and Drug Administration in May. The new initiatives for bioengineered foods stem in part from input the agency received during public outreach meetings held throughout the country late last year. They also build upon procedures FDA has been following since 1994 for ensuring the safety of these foods. (See "Are Bioengineered Foods Safe?" in the January-February 2000 FDA Consumer.)
FDA's plans include a proposal to require developers of bioengineered foods and animal feeds to notify the agency at least 120 days before they intend to market the products. Such consultation with FDA has been voluntary since these foods were first marketed in the early 1990s.
Although FDA believes it has been consulted on all bioengineered foods and feeds currently on the market, it is proposing to strengthen the current process by requiring specific information from manufacturers. The agency will evaluate that information in terms of product safety, labeling, and adulteration issues, and then provide manufacturers its conclusions about the regulatory status of the food or feed. Posting these conclusions and manufacturers' information on FDA's Website (www.fda.gov) will give consumers easy access to information on individual bioengineered products.
In a related step, FDA will enhance the ability of its food and veterinary medicine advisory committees to address scientific questions related to bioengineered foods and animal feeds by adding members with agricultural biotechnology expertise.
FDA also plans to draft guidance that will assist manufacturers who wish to voluntarily label their foods as being made with or without bioengineered ingredients. The guidelines will help ensure that labeling is truthful and informative. To receive maximum consumer input, FDA will use focus groups to help develop the guidelines and will seek public comment on the draft guidance.
Cancer found in sharks casts doubt on the usefulness of shark cartilage pills to cure or prevent cancer, scientists from Johns Hopkins University and George Washington University reported April 5 at the annual meeting of the American Association for Cancer Research. Proponents of shark cartilage supplements have believed that since sharks did not appear to get cancer, their cartilage may block the growth of new blood vessels that supply nutrients to a tumor and cause it to spread. The new data challenge that belief. The researchers examined data in the National Cancer Institute's Registry of Tumors in Lower Animals and found 40 cases of tumors in sharks and related fishes. Researchers noted that their study can't rule out the possibility that scientists may one day find a useful cancer treatment in cartilage from sharks or other animals.
Eating large amounts of tofu in midlife may be associated with mental deterioration in old age, according to the Hawaii Center for Health Research. An analysis of data from the Honolulu Heart Program found that men who ate the most tofu during their mid-40s to mid-60s showed the most signs of mental deterioration in their mid-70s to early 90s. The program began tracing the health of 8,000 Japanese-American men in 1965. Researchers said that both men and women eating tofu two or more times a week were up to twice as likely to show some signs of impaired mental function later in life than those who rarely ate tofu. The proposed link between eating tofu and decline in brain function is the isoflavones, chemicals in soy that affect an enzyme in the body that may block changes in the brain related to learning. (Journal of the American College of Nutrition, April 2000)
When the beer tax increases, the rates of gonorrhea among young people drop, according to a national study of state alcohol policy changes from 1981 to 1995 by the Centers for Disease Control and Prevention. CDC researchers estimate that a state tax increase of 20 cents on a six-pack of beer could reduce U.S. gonorrhea rates by almost 9 percent. Two-thirds of the states that increased the beer tax were found to have decreased gonorrhea rates among teens aged 15 to 19 the year following the tax hike. Nearly three-quarters of the tax increases were associated with decreased gonorrhea rates among young adults aged 20 to 24. Gonorrhea rates among teens were also found to drop in states that increased their legal drinking age. These findings are consistent with other studies that link alcohol consumption to risky sexual behavior among youth. (Morbidity and Mortality Weekly Report, April 28, 2000)
Consuming megadoses of dietary antioxidants does not prevent chronic diseases, concluded the experts on the Institute of Medicine's (IOM) Food and Nutrition Board. According to the April 2000 report on Dietary Reference Intakes, high doses of the nutrients vitamin C, vitamin E, selenium and beta-carotene do not protect the body from a variety of illnesses, such as cardiovascular disease, diabetes, and various forms of cancer, nor do they prevent basic nutritional deficiencies. In fact, the opposite may be true. Extremely high doses of antioxidants may lead to health problems, including diarrhea, bleeding, and the risk of toxic reactions.
In recent years, researchers have focused on the possible role that dietary antioxidants play in promoting and maintaining health. Antioxidants help neutralize potentially damaging molecules--byproducts of the body's metabolism--that may damage critical cellular components, including genes. Antioxidants can help prevent the damage.
But after a comprehensive review of the scientific evidence, the IOM's Food and Nutrition Board, which is part of the National Academy of Sciences, concluded that although a large number of population studies reveal a link between a diet rich in foods containing antioxidants, such as fruits and vegetables, and a lower incidence of certain chronic diseases, they cannot be certain that antioxidants are the reason.
Since 1941, the Food and Nutrition Board has set Recommended Dietary Allowances (RDAs) for the types and quantities of nutrients that are needed for healthy diets. The board has updated and expanded the system over the past several years for determining these values--now called Dietary Reference Intakes, or DRIs. The 2000 report, "Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids," is the latest in a series on DRIs.
"These IOM reports are a major source of scientific information for nutrition labeling," says Elizabeth Yetley, lead scientist in FDA's Center for Food Safety and Applied Nutrition. "They are an authoritative source, independent of the agency, and not influenced by regulatory applications."
To determine how much of a specific nutrient one needs on a daily basis, the board considers two types of numbers: the RDA--a daily intake goal for healthy individuals, and the "tolerable upper intake level"--the largest amount of a nutrient that healthy individuals can take each day without risking adverse health effects.
Although this is the first time the science board has raised the daily recommended levels for the nutrients vitamin C and vitamin E, scientists continue to struggle with whether beta-carotene and other carotenoids are true dietary antioxidants. Laboratory tests show only that carotenoids have antioxidant properties, but the results of human trials searching for health benefits have been inconsistent. The only clear role of carotenoids, according to the board, is in the formation of vitamin A.
Norman I. Krinsky, Professor of Biochemistry at Tufts University School of Medicine, says that most North American adults get enough vitamin C, vitamin E, and selenium from their normal diets to meet current recommendations. Those who don't, he adds, could get enough of these nutrients by simply improving their diets.
Sleep apnea and other breathing problems during sleep are associated with high blood pressure, according to the results of a large multicenter study of individuals 40 years of age and older. Scientists from Johns Hopkins University and other research institutions found that the highest numbers of sleep-disordered breathing episodes each hour were more likely to occur in people with high blood pressure. (Journal of the American Medical Association, April 12, 2000)
A vaccination aimed at an enzyme common to a number of human tumors might enable the body's immune system to attack and kill cancer cells. A team of scientists at the University of California, San Diego, working with colleagues at the Institut Pasteur in Paris, successfully used a vaccine in the test tube and in mice to activate a type of white blood cell to destroy cancer cells. The vaccine's target is telomerase, an enzyme key to the uncontrolled replication of cancer cells. Because telomerase is also essential to the functioning of normal cells, the scientists looked for negative effects of the vaccine on these cells--and found none. They predict that the telomerase levels in normal cells are low, causing little danger of the body attacking its own normal cells. The researchers do, however, acknowledge that this and other potential problems require further study. (Proceedings of the National Academy of Sciences, April 25, 2000)
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