Investigation of previously reported mucosal swellings after injection with Citanest Forte

The purpose of this study was to determine the reason for an apparent increase in the number of mucosal swellings after maxillary infiltration with Citanest Forte (prilocaine HCl 4% solution with epinephrine 1:200,000), 2 years after its introduction in 1971 by Astra Pharmaceutical Co (now AstraZeneca) in the United States. Approximately 70% of these reported reactions were from California, where less than 11% of all cartridges were sold. Comparison with New York State, with 27% of total sales but less than 1% of the reactions, suggested that possible differences in practice characteristics were responsible for the swellings. On the basis of the Bureau of Economic Research and Statistics Survey of Dental Practice, dentists in the Far West (eg, California) were found to schedule appointments with a median length of approximately twice that of their Mid-East colleagues, the implication being that more anesthetic solution was injected per office visit. Follow-up telephone interviews of dentists reporting such reactions at that time verified that they administered more than the recommended 1.8-mL dose. The most important epidemiologic information was that prilocaine HCl 4% solution with epinephrine 1:200,000 had been on sale in Canada 4 years before it was introduced in the US market, with little or no evidence of drug-related effects. Comparison of the US and Canadian prilocaine HCl with epinephrine 1:200,000 specifications revealed that NaCl was added to an already hypertonic prilocaine solution in the US but not in Canada. Comparison of the responses to intradermal injection of US and Canadian prilocaine solutions into the backs of rabbits with follow-up studies of dose-related NaCl injections demonstrated that the added NaCl was responsible for the onset and duration of irritation from the initially marketed US Citanest solutions.