EFFECTS OF METAMIZOL ON NOCICEPTIVE RESPONSES TO STIMULATION OF THE URETER AND ON URETER MOTILITY IN ANESTHETIZED RATS

In this study, we have examined the effects of metamizol (dipyrone), a non-opioid analgesic which is effective in relieving renal colic pain , on nociceptive responses evoked by stimulation of the ureter, on pye loureteral motility and on intraureter pressure after ureter obstructi on in anaesthetised rats. Metamizol (5-50mg/kg i.v.) dose-dependently inhibited reflex presser responses evoked by distensions of the ureter to pressures of 30, 55 and 75 mmHg for 30 s (ID50 = 8 +/- 1 mg/kg). M etamizol also dose-dependently reduced intraureter pressure during tot al ureter occlusion (25 mg/kg produced a reduction of 25% in 10 min). However, metamizol at doses up to 50 mg/kg had no effect on pyleourete ric motility (contraction amplitude, rate or intraureter pressure) und er normal pressure conditions. We conclude that metamizol has a direct antinociceptive action on pain of ureteric origin, and spasmolytic ef fects after ureter obstruction (but not under normal conditions) which may also contribute to pain relief.