Activating Cholinesterase-Inhibiting Drugs

List the locations and types of acetylcholine receptors in the major organ systems (CNS, autonomic ganglia, eye, heart, vessels, bronchi, gut, genitourinary tract, skeletal muscle, exocrine glands). 

Relate the different pharmacokinetic properties of the various choline esters and cholinomimetic alkaloids to their chemical properties. 

List the major clinical uses of cholinomimetic agonists. 

Describe the pharmacodynamic differences between direct-acting and indirect-acting cholinomimetic agents. 

List the major signs and symptoms of (1) organophosphate insecticide poisoning and (2) acute nicotine toxicity. 

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AccessMedicine Print Chapter 7. Cholinoceptor-Activating Cholinesterase-Inhibiting Drugs... 

CHOLINOCEPTOR-ACTIVATING CHOLINESTERASE-INHIBITING DRUGS INTRODUCTION... 

AccessMedicine Print Chapter 7. Cholinoceptor-Activating Cholinesterase-Inhibiting Drugs muscle. Life Sci 2003 74 355. [PMID 14607264]... 

Blood vessels receive no direct innervation from the parasympathetic nervous system. However, parasympathetic nerve stimulation dilates coronary arteries, and sympathetic cholinergic nerves cause vasodilation in the skeletal muscle vascular bed (see Chapter 6 Introduction to Autonomic Pharmacology). Atropine can block this vasodilation. Furthermore, almost all vessels contain endothelial muscarinic receptors that mediate vasodilation (see Chapter 7 Cholinoceptor-Activating Cholinesterase-Inhibiting Drugs). These receptors are readily blocked by antimuscarinic drugs. 

Insecticides derived from natural sources include nicotine, rotenone, and pyrethrum. Nicotine is obtained from the dried leaves of Nicotiana tabacum and Nicotiana rustica. It is rapidly absorbed from mucosal surfaces the free alkaloid, but not the salt, is readily absorbed from the skin. Nicotine reacts with the acetylcholine receptor of the postsynaptic membrane (sympathetic and parasympathetic ganglia, neuromuscular junction), resulting in depolarization of the membrane. Toxic doses cause stimulation rapidly followed by blockade of transmission. These actions are described in Chapter 7 Cholinoceptor-Activating Cholinesterase-Inhibiting Drugs. Treatment is directed toward maintenance of vital signs and suppression of convulsions. 

Malathion is an organophosphate cholinesterase inhibitor that is hydrolyzed by plasma carboxylesterases much faster in humans than in insects, thereby providing a therapeutic advantage in treating pediculosis (Chapter 7 Cholinoceptor-Activating Cholinesterase-Inhibiting Drugs). Malathion is available as a 0.5% lotion (Ovide) that should be applied to the hair when dry and the hair then combed to remove nits and lice after 4-6 hours. 

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