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.