ADRENERGIC BLOCKING AGENTS
8-1. INTRODUCTION TO ADRENERGIC BLOCKING AGENTS
a. In the last lesson, the topic of adrenergic (sympathomimetic) agents was
discussed. As you will recall, this group of drugs produces effects like those produced
b. This lesson will focus on the topic of adrenergic blocking agents. This group
of agents blocks or interferes with the types of responses typically caused by the
transmitters of the adrenergic (sympathetic) nervous system. Adrenergic blocking
agents are sometimes referred to as sympatholytic agents.
8-2. GENERAL MECHANISMS OF ACTION OF ADRENERGIC BLOCKING
There are two basic categories of mechanisms of action demonstrated by
adrenergic blocking agents.
a. Some adrenergic blocking agents inhibit the synthesis, storage, or release of
norepinephrine. Therefore, less norepinephrine is available to the receptors to produce
its effects (adrenergic stimulation).
b. Other adrenergic blocking agents inhibit the reaction between norepinephrine
and the receptor.
8-3. PRINCIPAL TYPES OF ADRENERGIC RECEPTORS
a. Alpha-Receptors. Alpha-receptors produce salivation, sweating, and
contraction of smooth muscle (except in the gastrointestinal tract).
b. Beta-Receptors. Beta-receptors increase the frequency and strength of the
heartbeat and cause relaxation of smooth muscle (except In the gastrointestinal tract).