Update on the incidence of metamizole sodium-induced blood dyscrasias in Poland.

Metamizole sodium (metamizole) is a popular non-opioid analgesic and a common non-prescription product in Poland. Controversy exists regarding the level of risk of agranulocytosis or aplastic anaemia associated with its use. Two previous pharmacovigilance studies conducted in Poland found the risk was low. Twenty-four of the 25 haematology centres that provide specialist care for the 30 million adults in Poland participated in this prospective 12-month study. Twenty-one cases of agranulocytosis, 48 of aplastic anaemia, 15 of neutropenia and 11 of pancytopenia were reported. Of these cases, three (two agranulocytosis; one aplastic anaemia) were judged as being possibly related to metamizole. Crude estimates of the rate of agranulocytosis and aplastic anaemia associated with metamizole were 0.16 and 0.08 cases/million person-days of use, respectively. Ongoing national safety surveillance in Poland shows that, despite the possibility of drug-induced blood dyscrasias with metamizole, the risk is very low.