Lawsuits alleging that zinc in two popular denture creams damages nerves, combined with the recent recall of some zinc-containing Zicam products, could call into question the use of the mineral, which trade groups insist is safe when taken appropriately.

More than 30 cases in a class action suit allege GlaxoSmithKline and Procter & Gamble failed to warn consumers their denture adhesives Poligrip and Fixodent contain zinc, which in excess can deplete copper levels in the body and cause neurological problems, loss of bone marrow function and other serious ailments, said Scott Weinstein, co-lead counsel in the class action suit and plaintiff liaison counsel.

He explained some consumers suffer zinc toxicity from swallowing some of the cream when they affix their dentures. The mineral then is absorbed through the gastrointestinal tract, not through the gums. Because the manufacturers did not label the creams as including zinc, many consumers' physicians could not easily identify the problem - resulting in a "medical mystery" and incorrect or delayed diagnoses, he added.

GSK and P&G acknowledge their products include a small amount of zinc for improved adhesive strength. However, P&G says in a statement, "the amount of zinc a consumer would ingest from daily usage of Fixodent is less than the amount of zinc in most daily multivitamins and comparable to 6 ounces of ground beef."

The Consumer Healthcare Products Association adds in a statement, "Zinc-containing denture adhesive products are safe and effective when used according to the labeled directions," which all CHPA members "explain - in words - and demonstrate - in pictures."

Indeed, the four patients who suffered zinc toxicity in a 2008 study in the Neurology journal, on which the class action partly is based, used drastically more than the recommended amount of adhesive. They used two or three tubes per week, and a tube should last three to 10 weeks when used according to directions.

Like the study participants, GSK says in a statement, the case reports also "involved excessive use or misuse of denture adhesive on a chronic basis. ... Consumers should not use or misuse denture adhesive to compensate for poorly fitting dentures and should see their dentist regularly to ensure their dentures are fitted properly."

The U.K.-based company adds when Poligrip is used as directed, "the amount of zinc that might be swallowed is small and is not harmful."

Weinstein did not confirm whether the consumers suing the manufacturers used the adhesives according to the directions, but said he "rejects the concept of overuse of the product because I believe that both defendants were well aware of how consumers used the product and that they sell more if consumers use more."

Plus, he added, neither company educated consumers about the risk of using the product.

He wants FDA to require the firms to include on the label a warning about zinc toxicity and to list zinc as an ingredient "so it is not a medical mystery when physicians find a high level of zinc in patients and can't figure out the source."

FDA did not comment on what, if anything, it would do in response to the cases.

The agency regulates denture adhesive as a class I medical device, which means it is subject only to general controls and firms are not required to list ingredients on the label.

Still, P&G updated its Web site to include information about zinc. In addition, Fixodent packaging "will soon provide detailed information to our consumers," the company says in a statement.

GSK also updated its Web site to include information about zinc in Poligrip. It added leaflets to the denture cream packaging that discuss the reports of possible problems from overuse and will add similar language to packages soon, according to reports.

GSK notes approximately 14 million people in the U.S. use denture cream, and Weinstein acknowledged zinc toxicity is very rare. He said his firm Morgan & Morgan tested more than 10,000 potential cases of zinc poisoning from denture cream and "only a handful were positive."

He anticipates filing a "few thousand" cases, which he expects to try beginning mid-2010.

The federal court cases were joined as a class action in June, just days before FDA warned consumers not to use three of Matrixx Initiatives' Zicam intranasal zinc-containing products because they posed a risk of loss of smell. Matrixx recalled the three products - Zicam brand Cold Remedy Nasal Gel, Cold Remedy Swabs and the discontinued children's size Cold Remedy Swabs (¹ Also see "Zicam Case Shows FDA Takes Defining Adverse Events Seriously" - Pink Sheet, 22 June, 2009.).

Suits Threaten Rep Of Other Products With Zinc

The class action suits "add another layer of concern about Zicam" products with orally consumed zinc because consumers suing GSK and P&G also orally consumed zinc in the denture creams, said Donald Kay Riker, president and founder of On Point Advisors.

Riker noted on his blog, OTC Product News, the denture cream cases raise "awareness of possible collateral damage to other OTC products and concern over how certain OTC product forms are regulated by FDA."

He explained in an interview these incidents may be "a canary in the coal mine" for zinc-containing products because they demonstrate "chronic exposure to zinc, whether through dietary supplements or homeopathic products or denture creams can lead to ... serious medical problems."

However, Daniel Fabricant, interim executive director and CEO of the Washington-based Natural Products Association, said comparing the denture cream and Zicam cases to supplements is like "comparing apples and oranges," because neither product is a supplement and they are used differently.

He explained the adverse events in the Zicam case were "a function of nasal sprays and not zinc." The denture creams are administered differently than supplements and, therefore, behave kinetically different, Fabricant said.

He added there are hundreds of studies that demonstrate the safety of zinc supplementation.

The Council for Responsible Nutrition agrees "these cases of recalls and litigation should not impact consumers' use of zinc supplements that are formulated to contain less than the" established upper limit of zinc.

According to the Institute of Medicine, the upper limit for zinc for adults is 40 mg, which is "far below those levels to which people were exposed in some of those cases, probably in the range of hundreds of [milligrams] or more," CRN's VP of Scientific and Regulatory Affairs Andrew Shao said in a statement.

He added the daily value for zinc is 15 mg per day and most multivitamins contain 100 percent of the daily value or less for zinc, which is also far below the harmful amount.

GSK says Super Poligrip contains 38 mg of zinc per gram, or less than 4 percent zinc, and P&G does not say in the frequently asked question section of its Web site how much zinc is in Fixodent. But, the Neurology study found zinc concentrations ranging from 17,000 ug to 34,000 ug per gram in Fixodent and Poligrip denture creams.

- Elizabeth Crawford ( ² e.crawford@elsevier.com )

Zinc Lawsuits, Recalls May Taint Mineral's Image

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