In this randomized study, the efficacy of i.v.
patient-controlled analgesia (PCA) was determined for the
opioid piritramide (a pure
mu-receptor agonist) and the
antipyretic analgesic metamizole (
Dipyrone) in three groups of patients following abdominal surgery. The doses of
piritramide were 1.5 mg (40 patients) and 3 mg (40 patients) on demand. In addition, we studied the effect of 71 mg
metamizole in combination with on-demand boluses of 1.5 mg
piritramide in 40 patients. During PCA we estimated the degree of
analgesia (verbal gain rating scale, visual analog scale) and monitored the ventilation, vigilance, and typical
drug side effects over a period of 24 h. The individual demand for
analgesic drugs varied markedly. The mean consumption of
piritramide during the study was 46.5 mg in the group with 1.5 mg per bolus and 68.6 mg in the group with 3.0 mg. The resulting
pain relief was satisfactory in both groups. The combination of
piritramide 1.5 mg and
metamizole 71 mg per bolus resulted in a reduction of mean
Piritramide-consumption to 44.1 mg, and the
pain relief was similar to that produced in the group treated with 3 mg
piritramide per bolus. The intensity of typical side effects of
opioids and
antipyretic analgesics (
nausea,
vomiting, lowering of respiratory frequency, sweating) was low and always easily controlled. The acceptance by patients, nurses, and physicians of PCA was high. PCA with on-demand
intravenous injection of the combination of
piritramide and
metamizole improved the degree of
analgesia and concomitantly reduced the
opioid dose.