Rare but serious risks associated with non-narcotic analgesics: clinical experience

Our data show that 1% of patients who required hospital treatment did so due to severe adverse reactions to analgesics. The most frequent adverse reaction was major gastrointestinal bleeding after aspirin, indomethacin, phenylbutazone or naproxen. Thrombocytopenia, second in frequency, was also mainly a complication of aspirin treatment, as was severe vertigo and tinnitus. Allergic reactions and leucopenia or agranulocytosis occurring in single cases only were associated with the use of pyrazolones. Patients with nephropathy were usually taking phenacetin or one of the close derivatives paracetamol or bucetin. Intensive monitoring for adverse reactions to drugs in 6,000 hospitalised patients in medical wards showed that analgesics, although frequently used, did not lead to life-threatening reactions. Gastrointestinal and neurological side effects were the most commonly observed reactions and these occurred more often after aspirin, indomethacin or pentazocine than after dipyrone or tilidine. Preliminary data of an international case-control-study on agranulocytosis and aplastic anaemia suggest that the incidence of agranulocytosis was in the order of 2 to 3 per million users of analgesics per year. Agranulocytosis occurred predominantly with pyrazolones, with a mortality of 1 to 2 per 10 million users per year. A cohort study on the treatment of colic pain in general practice showed that serious events most likely due to adverse reactions to analgesics were bronchospasm, shock fragments or shock. The incidence of these serious events was about 2 in 1,000 treated cases. The relative risk was not increased by treatment with pyrazolones, opioids or other drugs.