VPT 421: Veterinary Toxicology (2+0)

PHYSIOLOGIC ANTAGONISTS

• Calcium
  • Calcium channel blockers reduce the influx of calcium into myocardial cells, resulting in impaired contractility with clinical manifestations of cardiac failure or hypotension.
  • Increasing the extracellular calcium concentration partly overcomes this blockade and reduces these toxic effects.
• Glucagon
  • Beta-blockers bind to cardiac beta-receptors and can cause bradycardia, heart block or impaired cardiac contractility. Since they bind with a very high affinity, they are difficult to be displaced with beta agonists.
  • Glucagon produces effects on myocardial cells that are similar to those of beta agonists, but it acts by binding to an unrelated class of receptors.
  • Glucagon is therefore effective even when there is profound beta blockade.