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POTASSIUM NITRATE IS CATEGORY I TOOTH DESENSITIZER INGREDIENT FOR OTC ORAL DISCOMFORT DRUGS; NO INGREDIENTS ARE CATEGORY I FOR TOOTHACHE RELIEF

Executive Summary

Potassium nitrate is a Category I (safe and effective) tooth desensitizer ingredient for OTC relief of oral discomfort drug products, FDA concludes in a Sept. 24 Federal Register notice of proposed rulemaking. Potassium nitrate previously had been recommended as a Category III (data are insufficient to classify as safe and effective) ingredient by FDA's OTC Dental Products Panel. Potassium nitrate (5%) is the active ingredient in Block Drug's Mint Sensodyne toothpaste and Promise toothpaste, and in Procter & Gamble's Denquel sensitive teeth toothpaste. The proposed rule says that "the agency has reviewed the data and concludes that there are sufficient data from two well- controlled clinical studies and three supportive studies to establish the effectiveness of 5% potassium nitrate as a tooth desensitizer." One study, testing the effectiveness of two potassium nitrate 5% toothpastes, was a placebo-controlled, double-blind, 12-week, three-way parallel study of 60 individuals. One method to assess hypersensitivity was use of a dental probe. At the end of the 12 weeks, "the potassium nitrate products caused mean reductions of hypersensitivity of 87% and 82% compared to a 54% reduction caused by the placebo." The proposed rulemaking amends the Tentative Final Monograph for OTC Oral Health Care Drug Products to incorporate the proposed rule for OTC relief of oral discomfort drug products. The oral health care TFM, which covers anesthetic/analgesic, astringents, debriding agent/oral wound cleansers and demulcents, was issued in January 1988 ("The Pink Sheet" Feb. 1, 1988, p. 3). Combining the two rulemakings into one "will result in more consistent labeling on these OTC products intended for topical use in the oral cavity and in less confusion for the manufacturers of these drug products and for the consumer," FDA said. A Category I classification is proposed for the combination of potassium nitrate with any Category I fluoride ingredient "used for the prevention of cavities and tooth desensitization." Block Drug said it is evaluating whether to add fluoride to the Mint Sensodyne and Promise toothpastes. Explaining the reasons for allowing such a combination product, FDA noted that it "is not currently aware of any chemical evidence predictive of an interaction between potassium nitrate and any Category I fluoride ingredient that would alter the bioavailability or effectiveness of either ingredient." Comments or requests for a hearing on the combination may be submitted to FDA by Nov. 25, 1991. Potassium nitrate is the only ingredient classified as safe and effective for use as a tooth desensitizer. The other five ingredients/combinations were classified as Category III (see chart next page). One oral mucosal analgesic ingredient, benzyl alcohol, was reclassified from the Dental Panel's recommendation of Category III to Category. Benzyl alcohol is an active ingredient in Lakeside Pharmaceuticals' Cepacol throat lozenges. Three other ingredients retained their Category I status as topical analgesics: benzocaine, phenol preparations (phenol and/or phenolate sodium), and butacaine sulfate. The oral health care TFM also has benzocaine, phenol preparations and benzyl alcohol listed as Category I anesthetic/analgesic ingredients. Benzocaine is contained in many oral analgesic products including Cepacol anesthetic lozenges, Whitehall's Anbesol products, Commerce's Orajel line and Rich-Vicks' Children's Chloraseptic Lozenges. Phenol is also an ingredient in Anbesol products, as well as in Lakeside's Cepastat sore throat lozenges, and in Chloraseptic products. None of the 13 ingredients listed for the relief of toothache were classfied as Category I. One ingredient, eugenol (85%-87%), was reclassified by FDA from a Category I ingredient to a Category III ingredient. FDA is requesting comments on how to best word a label warning about the potential for anaphylactic-like reactions associated with OTC oral health care products used to treat a sore throat. The notice says that in March 1990 FDA "became aware of four reports from the United Kingdom of life-threatening pharyngeal spasm that were related to a phenol-containing OTC spray" used to treat a sore throat. The incidents "occurred when people who may have had epiglottitis used the anesthetic/analgesic oral spray," FDA said. Subsequently, FDA asked Rich-Vicks for any adverse drug experience reports involving anaphylactic-like reactions with its Chloraseptic sprays in U.S. consumers. The company submitted 18 reports to the agency that involved Chloraseptic products, and other reports involving its OTC sore throat products that contain the analgesic ingredients benzocaine or menthol. From an analysis of the reports from Rich-Vicks and other manufacturers of OTC sore throat products, FDA documented 24 reactions involving phenol, four cases involving benzocaine, three involving benzyl alcohol, three involving menthol, 38 cases involving dyclonine hydrochloride and three cases involving hexylresorcinol, the notice says. Rich-Vicks informed FDA in February that it intends to strengthen the warning for its OTC sore throat products that contain an anesthetic/analgesic ingredient. The proposed revision reads: "If sore throat is severe, or is accompanied by difficulty in breathing, or persists for more than two days, do not use and consult a doctor promptly." The firm proposes to place this warning on its products "as current labeling inventory is exhausted." The agency said it believes that the number of reports of anaphylactic-like reactions "demonstrates the need for labeling to highlight this potential problem." FDA "seeks comment on whether 'difficulty in breathing,' 'noisy breathing,' or 'difficulty in swallowing' should be added to this warning." FDA also wants comments on whether revised warnings should apply only to drugs containing anesthetic ingredients or whether they should apply to any OTC sore throat product. Written comments or requests for a hearing on the proposed regulation may be submitted by Jan. 22, 1992. New data demonstrating the safety and efficacy of the conditions not classified in Category I are due by Sept. 24, 1992.
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