Prokinetic Agents and Other Stimulants of GI Contractility, Goodman & Gilman's Pharmacology , 11e.

Prokinetic Agents and Other Stimulants of GI Contractility

Direct activation of muscarinic receptors, such as with the older cholinomimetic agents (see Chapter 7), is not a very effective strategy for treating GI motility disorders because these agents enhance contractions in a relatively uncoordinated fashion that produces little or no net propulsive activity. By contrast, prokinetic agents are medications that enhance coordinated GI motility and transit of material in the GI tract. Although ACh, when released from primary motor neurons in the myenteric plexus, is the principal immediate mediator of muscle contractility, most of the clinically useful prokinetic agents act "upstream" of ACh, at receptor sites on the motor neuron itself, or even more indirectly, on neurons one or two orders removed from it. Although pharmacologically and chemically diverse, these agents appear to enhance the release of excitatory neurotransmitter at the nerve-muscle junction without interfering with the normal physiological pattern and rhythm of motility. Coordination of activity among the segments of the gut, necessary for propulsion of luminal contents, therefore is maintained.
Agents useful clinically in altering GI motility are considered below.

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