II. Background
-
Adrenergic Receptor
Agonists increase Blood Pressure
- Alpha 1 Adrenergic Receptor binding increases Vasoconstriction
- Beta 1 Adrenergic Receptor binding increases myocardial contractility
- Presynaptic Adrenergic Release Inhibitors lower Blood Pressure
- Central Acting Adrenergic Agonists
- Activate alpha-2 receptors that inhibit CNS sympathetic signals
- Results in increased parasympathetic effects and side effects
- Peripheral Acting Adrenergic Antagonists
- Block peripheral Norepinephrine release
- Central Acting Adrenergic Agonists
III. Preparations: Central Acting Adrenergic Agonists
- Mechanism
- See Alpha Adrenergic Receptor
- Bind central alpha-2 receptors (vasomotor receptors) to inhibit sympathetic outflow
- Decreases Peripheral Vascular Resistance (and Blood Pressure)
- Decreases Heart Rate
- Non-selective Preparations
- Selective Preparations: Alpha-2a (for Opioid Withdrawal symptoms)
IV. Preparations: Peripheral Acting Adrenergic Antagonists
- Mechanism
- Peripheral Presynaptic Adrenergic Antagonists block Norepinephrine release from postganglionic nerve terminals
- Contrast with Postsynaptic Adrenergic Antagonists that block peripheral alpha receptors
- Agents