Metamizole (dipyrone)-induced agranulocytosis: Does the risk vary according to ethnicity?

Based on spontaneous reports from Spain, it is claimed that the British, Irish and Scandinavians are at a greater risk of dipyrone-induced agranulocytosis. This report examines the evidence.

Although interethnic differences in drug response are well known, there are no reliable epidemiologic data to support the above claim. Available information on chlorpromazine suggests variable ethnic sensitivities to drug-induced agranulocytosis. Agranulocytosis induced by at least four drugs has been associated with variant HLA alleles. Preliminary evidence also suggests that the presence of specific variant HLA alleles may sensitize individuals to dipyrone-induced agranulocytosis. There are historical reasons to suspect that the three populations referred to may share some key genetic features, including the potentially culprit variant HLA alleles, that predispose them to dipyrone-induced agranulocytosis.

The possibility that the British, Irish and Scandinavians show higher susceptibility than other populations to dipyrone-induced agranulocytosis cannot be ruled out. If this complication is linked to specific HLA allele(s), populations with higher frequency of variant HLA allele(s) may be at a greater risk. If confirmed, screening for the risk allele may be useful in reducing the risk of dipyrone-induced agranulocytosis.