Chapter 20: Cholinergic Drugs

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Cholinergic Drugs
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Terms in this set (22)
Cholinergic Drugs
-drugs that stimulate the parasympathetic nervous system (PSNS) "Rest and Digest"

-mimic effects of the PSNS neurotransmitter acetylcholine (ACh)
Cholinergic Receptors:
Nicotinic receptors
-located in the ganglia of both the PSNS and SNS

-named nicotinic b/c they can be stimulated by the alkaloid nicotine
Cholinergic Receptors:
Muscarinic receptors
-located postsynaptically in the effector organs of the PSNS (smooth muscle, cardiac muscle, glands)

-named muscarinic b/c they can be stimulated by the alkaloid muscarine
Mechanism of action:
direct-acting
-cholinergic agonists

-bind to cholinergic receptors, activating them
Mechanism of action:
indirect-acting:
-cholinergic agonists

-inhibit the enzyme acetlycholinesterase, which breaks down ACh

-results in more ACh available at the receptors
Indirect-acting
Cholinesterase inhibitors
-reversible: bind to cholinesterase for a period of minutes to hours

-irreversible: bind to cholinesterase and form a permanent covalent bond

-irreversible: long duration of activity
*the body must make new
cholinesterase to break
these bonds
Drug effects
-effects seen when PSNS is stimulated

-stimulate intestine and bladder: increased gastric secretions, increased GI motility, increased urinary frequency

-stimulate pupils: constriction, reduced intraocular pressure

-increased salivation and sweating

-cardiovascular: decreased Hr, vasodilation

-respiratory: bronchial constriction, narrowed airways
recommended dose of cholinergic drug
-primarily affect muscarinic receptors
-desired effect
High dose of cholinergic drug
-stimulate nicotinic receptors
-many udesirable effects are caused by stimulation of nicotinic receptors
The nurse is assessing a patient who has been taking a cholinergic drug for 3 days. The patient has flushed skin, orthostatic blood pressure changes, and is complaining of abdominal cramps and nausea. The nurse recognizes that the patient is most likely experiencing

a.) early signs of a cholinergic crisis.
b.) late signs of a cholinergic crisis.
c.) an allergic reaction to the drug.
d.) expected adverse effects.
-Correct answer: A

-Rationale: The items listed are early signs of a cholinergic crisis, which can become more severe and lead to hypotension, circulatory collapse, bloody diarrhea, shock, and cardiac arrest (late signs).
Indications: direct-acting drugs-reduce intraocular pressure -useful for glaucoma and intraocular surgery -topical application is best b/c of poor oral absorptionIndications: bethanechol (direct-acting drug)-increases tone and motility of bladder and GI tract -relaxes sphincters in bladder and GI tract, allowing them to empty -helpful for post-surgical atony of the bladder and GI tract -oral dose or subQ injectionIndications: indirect-acting drugs-cause skeletal muscle contractions -used for dx./tx. of myasthenia gravis -used to reverse neuromuscular blocking drugs -used to reverse anticholinergic poisoning (antidote)Indications: indirect-acting anticholinesterase drugs-used for tx. of mild to moderate Alxheimer's disease, prevents break down of ACh -drugs: *donepezil (aricept) *galantamine (Razadyne) *rivastigmine (Exelon)Adverse effects-result of overstimulation of the PSNS -cardiovascular: bradycardia, hypotension, syncope, conduction abnormalities (AV block and cardiac arrest) -CNS: headache, dizziness, convulsions, ataxia -GI: abdominal cramps, increased secretions, n/v -Respiratory: increased bronchial secretions, bronchospasms -Other: lacrimation, sweating, salivationInteractions-anticholinergics, antihistamines, sympathomimetics -other cholinergic drugs: additive effectsA patient with myasthenia gravis is scheduled to have lunch at 1200. The nurse will administer the pyridostigmine (Mestinon) at what time for optimal therapeutic effect? a.) 1100 b.) 1130 c.) 1200 d.) 1230Correct answer: B Rationale: The drug should be taken 30 minutes before a meal for maximal therapeutic effect.Nursing implications Atropine-antidote for cholinergics -should be available in pts. room for immediate use if neededCholingergic crisis-abdominal cramps, flushing of skin, n/v, hypotension, circulatory collapse, cardiac arrestTherapeutic effects-alleviated s/s of myasthemia gravis -in postoperative pts. w/decreased GI peristalsis, monitor for: *increased bowel sounds *passage of flatus *occurrence of bowel movementsTherapeutic effects: urinary retention/hypotonic bladder-urination should occur w/in 60mins of bethanechol adminTherapeutic effects: Alzheimer's diesease-improvement in symptoms -improvement in mood and decrease in confusion