Pharmacodynamics of intrathecal and epidural fadolmidine, an α2-adrenoceptor agonist, after bolus and infusion in dogs-comparison with clonidine.

Abstract

An α2-adrenoceptor agonist, clonidine, is extensively used in both anesthesia and intensive care medicine. However, clonidine may produce pronounced hemodynamic side effects such as hypotension and bradycardia which may limit its usefulness in certain conditions. Fadolmidine is a potent α2-adrenoceptor agonist with different physicochemical properties than clonidine. Here, the effects of fadolmidine and clonidine on analgesia (an increase in thermal skin twitch response latency), sedation, blood pressure, heart rate, respiratory rate, and body temperature were evaluated either up to 8 h after either intrathecal or epidural bolus injections or during a 24-h continuous intrathecal infusion at equipotent analgesic doses in non-anesthetized Beagle dogs. Fadolmidine and clonidine produced a dose-dependent and equipotent maximal antinociception after intrathecal bolus injection (ED50: 67 μg and 78 μg, respectively), but the duration of action of fadolmidine was more long-lasting. During the intrathecal infusion, fadolmidine achieved a good analgesic effect without evoking cardiovascular side effects, e.g., hypotension; these were evident during clonidine infusion. Epidurally, the antinociceptive potency of fadolmidine was weaker (ED50: 128 μg) than when intrathecally administered and weaker than that of epidural clonidine (ED50: 51 μg). At analgesic doses, fadolmidine injection induced moderate initial hypertension concomitantly with a decrease in heart rate whereas clonidine evoked hypotension and bradycardia. These results suggest that especially when non-opioid long-term pain relief is needed, an intrathecal infusion of fadolmidine can provide long-term antinociception with less of the known use-limiting adverse effects associated with clonidine.

• Authors: Tiina Leino, Tony Yaksh, Kjersti Horais, Antti Haapalinna
• Journal: Naunyn-Schmiedeberg's archives of pharmacology (Naunyn Schmiedebergs Arch Pharmacol) Vol. 393 Issue 8 Pg. 1459-1473 (08 2020) ISSN: 1432-1912 [Electronic] Germany
• PMID: 32179953 (Publication Type: Comparative Study, Journal Article)

Chemical References

• Adrenergic alpha-2 Receptor Agonists
• Analgesics
• Imidazoles
• Indans
• Clonidine
• radolmidine

Topics

• Adrenergic alpha-2 Receptor Agonists (administration & dosage, toxicity)
• Analgesics (administration & dosage, toxicity)
• Animals
• Blood Pressure (drug effects)
• Body Temperature Regulation (drug effects)
• Clonidine (administration & dosage, toxicity)
• Dogs
• Heart Rate (drug effects)
• Imidazoles (administration & dosage, toxicity)
• Indans (administration & dosage, toxicity)
• Infusions, Spinal
• Injections, Epidural
• Injections, Spinal
• Male
• Pain Threshold (drug effects)
• Respiratory Rate (drug effects)