Beta-Blocker Poisoning

Basics

Normal Physiology

Cardiovascular: β₁-receptors:
- ATP converted to cAMP by adenyl cyclase with stimulation of β-receptors
- cAMP activates protein kinase, which phosphorylates proteins of the sarcoplasmic reticulum
- Sarcoplasmic reticulum releases calcium
- Excitation–contraction coupling occurs
Effects of β-blockers:
- Cardiovascular:
  - Decreased excitation/contraction
  - Membrane stabilizing activity
  - Sodium channel blockade causes a prolongation of the QRS complex (with some agents)
  - Prolongation of QTc interval leading to ventricular dysrhythmias (with some agents)
  - Intrinsic sympathomimetic activity
  - Partial agonist properties (with some agents)
- Neurologic:
  - CNS effects with the lipophilic agents (propranolol, metoprolol, labetalol)

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