Drugs That Act on the Autonomic Nervous System
Actions
of drugs affecting the PNS can be organized on the basis of
ANS anatomy and the neurotransmitter receptors that mediate physiologic
responses to endogenous ACh and norepinephrine. Sympathetic effects can be
produced by drugs that either enhance sympathetic tone (sympathomimetics such
as adrenoceptor agonists) or depress parasympathetic tone (cholinergic receptor
antagonists). Parasympathetic effects can be produced by
drugs that either enhance parasympathetic tone or depress sympathetic
tone. Drugs enhancing neurotransmitter action by activating receptors are known
as direct acting; drugs enhancing neurotransmitter action by some other
means, eg, by inhibiting enzymes that degrade the neurotransmitter, are known
as indirect acting.
