Operational criteria for adverse drug reactions in evaluating suspected toxicity of a popular scabicide.

A recently developed algorithm for the diagnosis of adverse drug reaction (ADR) was used to investigate the quality of evidence in reported cases of ADRs to 1% gamma benzene hexachloride (GBH), a popular scabicide and pediculicide currently under suspicion as a cause of central nervous system (CNS) toxicity, especially in children. Of the 53 reported cases of alleged toxicity, 37 were associated with lindane insecticide (greater than 1% GBH), which is not a pharmaceutical preparation. Of these 37 cases, 34 scored as definite or probable reactions on the algorithm. Of the 26 reports associated with the drug, 1% GBH, none scored as definite and only 6 as probable ADRs. Of these 6 probable cases, 5 represented inappropriate application or unintended ingestion. The use of rigorous operational criteria, such as those developed in this algorithm, permits a scientifically disciplined assessment of whether or not a drug has been fairly indicted, and also provides valuable clinical information about other aspects of suspected drug toxicity.