Indirect-Acting Cholinergic Agnoists
- React with acetylcholinesterase preventing Ach from breaking down – results in ↑ Ach
- May bind reversibly or irreversibly
- Irreversible:
- Being developed to as nerve gas to be used as weapons
- War setting – antidote readily available
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Indications:- Myasthenia gravis (autoimmune disease of progressive muscle weakness / lack of muscle control)
- Alzheimer's (there is a progressive loss of ACh-producing neurons & their target neurons)
Contraindications:
Caution:
Adverse Reactions:
Nursing Mgmt
Atropine; works in CNS
Adverse Effects
- Allergy
- Bradycardia
- Intestinal or urinary tract obstruction
- Lactation
Caution:
- Any condition that could be exacerbated by cholinergic stimulation
- Asthma, CAD, PUD, arrhythmias, epilepsy, or parkinsonism
Adverse Reactions:
- Bradycardia, Hypotension
- Bronchoconstriction
- ↑ bladder tone
- ↑ GI secretions & activity
- Relaxation of GI & GU sphincters
- Pupil constriction (miosis)
Interactions:
Kinetics:
- ↑ risk GI bleed if used w/ NSAIDs
- ↓ anticholinesterase effects if taken w/ any cholinergic drugs because these work in opposition to each other
- ↑ theophylline levels w/ tacrine
Kinetics:
- Well absorbed and distributed throughout the body
- Metabolized in the liver and excreted in the urine
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Drugs to Treat Myesthenia gravis:
1. Neostigmine (Prostigmine) - works at neuromuscular junction
2. Pyridostigmine (Regonol, Mestinon) - longer duration than neostigmine
3. Ambenonium (Mytelase) - only PO; cannot be used if patient is unable to swallow
4. Edrophonium (Tensilon, Enlon) - diagnostic agent for myasthenia gravis
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Drugs to Treat Alzheimer's:
1. Tacrine (Cognex) - 1st drug out there to treat Alzheimer's
2. Galantamine (Reminyl) - used to stop Alzheimer's progression
3. Rivastigmine (Exelon) - available in solution for swallowing ease
4. Donepezil (Atricept) - once-a-day dosing!
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Nursing Mgmt
- if IV administer slowly
- Atropine sulfate on-hand in case of crisis (antidote)
- Observe for excessive salivation, diarrhea, emesis, excessive urination
- should be taken w/ meals
- Prevent injury
- Teaching
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Nerve Gas – Irreversible Indirect Cholinergic Agonist:
Antidotes:
- Irreversible acetylcholinesterase inhibitor
- Leads to toxic accumulation of ACh at cholinergic receptor sites
Antidotes:
Pralidoxime (Protopam Chloride); works in PNS
- IM or IV
- frees up acetylcholinesterase to start breaking down ACh
- on-hand for MG receiving an IDCA
- antidote for irreversible acetylcholinesterase-inhibiting drugs, or nerve gas
- Organophosphate pesticide poisoning
Atropine; works in CNS
- Block cholinergic activity & active Ach in CNS
- Activate Acetylcholinesterase to breakdown Ach
Adverse Effects
- Blurred vision, dizziness, diplopia, headache, hyperventilation
- Can cause parasympathetic crisis and muscle paralysis
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