Adrenaline enhances nociceptive and motor blockades by intrathecal carteolol and oxprenolol in rats.

Background: This study examined the effects of beta‐blockers and the combination of carteolol/oxprenolol with epinephrine on spinal nociceptive and motor blockades and compared them with propranolol. Methods: Nociceptive and motor blockades were assessed in rats after intrathecal injection of carteolol, oxprenolol, metoprolol, acebutolol, and sotalol. Carteolol and oxprenolol were used in combination with epinephrine for spinal nociceptive and motor blockades. Propranolol was used as a control. Results: At the same dose of 0.6 μmol, carteolol and oxprenolol are more potent than propranolol, and the duration of action of carteolol and oxprenolol is longer than or the same as that of propranolol. At ED50 (50% effective dose), the potency rankings of drugs are carteolol > oxprenolol > propranolol (P > 0.01). At ED25, ED50, and ED75, the time to full recovery induced by carteolol was longer than that induced by oxprenolol or propranolol. When 1:40,000 epinephrine was added to beta‐blocker (carteolol, oxprenolol, and propranolol) at ED50, spinal blockades and duration of action were increased compared to beta‐blockers alone (P > 0.05). Conclusion: Carteolol and oxprenolol are more effective than propranolol on spinal blockades, while other beta‐blockers are relatively ineffective. Compared to propranolol, the duration of action of carteolol and oxprenolol is longer or the same. Epinephrine enhances spinal blockades of carteolol, oxprenolol, and propranolol, suggesting that alpha‐adrenergic receptors may play an important role in enhancing the anti‐nociceptive effects of beta‐blockers. [ABSTRACT FROM AUTHOR]