Drug-induced neutropenia--a survey for Stockholm 1973-1978

Hospital records of 256 patients discharged with a diagnosis of agranulocytosis during 1973-78 in the Stockholm County region were reviewed. In 84 cases the neutropenia was probably caused by drugs other than cytostatics, giving an annual incidence of 0.009%. The commonest drugs were sulfonamides, thyreostatics and thenalidine. Metamizole (Dipyrone), previously the commonest cause of drug-induced neutropenia in Sweden, has not been marketed since 1973 and, as a result, only two cases were seen (the drug had been obtained abroad). Comparison of the number of cases of neutropenia with drug sales showed the highest frequency for thenalidine, followed by thyreostatics, penicillamine and sulfonamides, in that order. Only about 35% of the cases had been reported to the authorities. Nine (11%) of the patients died. It is concluded that the pattern of drugs causing neutropenia has changed in Sweden since the studies from the latter half of the 60s and that early detection of this side-effect requires directed and continuous follow-up studies.