Cholinergic Drugs Flashcards
What are the two types of cholinergic receptors and where are the found?
Nicotinic
- In ganglia of both SNS and PNS
- Also in adrenal medulla to release epinephrine
- Skeletal muscle neuromuscular junctions
- CNS
- Stimulated by nicotine
Muscarinic
- In effector tissues of PNS (smooth muscle, cardiac cells, glands)
- CNS
- Stimulated by a poisonous mushroom compound muscarine
What is the function of cholinergic activators?
To stimulate cholinergic pathways in PNS and the cholinergic system in CNS
Also known as agonists or “parasympathomimetics”
Mimic the effects of cholinergic neurotransmitter acetylcholine (ACh)
What’s the difference between direct-acting and indirect-acting cholinergic agonists?
Direct:
- Bind to cholinergic receptors to activate them
Indirect:
- Inhibit the enzyme cholinesterase that breaks down ACh in synapse
- Results in more ACh available to activate postsynaptic receptors
How are cholinesterase inhibitors used in skeletal muscles?
For skeletal muscles:
- Causes skeletal muscle contraction
- Used for diagnosis and treatment of myasthenia gravis (autoimmune condition that attacks nicotinic receptors in skeletal muscle neuromuscular junction, includes muscle weakness and drooping eyelids)
- Reverse neuromuscular blocking agents
- Antidote for anticholinergic poisoning
What are the effects of cholinesterase inhibitors?
Makes ACh last longer in the synapse because cholinesterase enzyme is inhibited
When do cholinesterase inhibitors affect muscarinic vs. nicotinic receptors?
Muscarinic receptors are impacted at lower doses
- Mimics actions of PNS
Nicotinic receptors are stimulated at high doses
- Acts in skeletal muscles
What are the adverse effects of cholinesterase inhibitors (SLUDGE)
SLUDGE
Salivation Lacrimation (tears) Urinary incontinence Diarrhea Gastrointestinal cramps Emesis
Also includes pupil constriction, increased intraocular pressure, decreased heart rate, and bronchial constriction/narrowed airways
How are cholinesterase inhibitors used in treating Alzheimer’s?
Alzheimer’s is caused by a loss of cholinergic neurons
- Donepezil (Aricept) is an indirect acting agent
- Helps to increase or maintain memory and learning capabilities
- 3-6 weeks for therapeutic effect
What are 2 direct acting agents (cholinergic agonists) and what do they treat?
- Pilocarpine
- Treats glaucoma by reducing intraocular pressure in eye
- Bethanechol
- Aids bladder emptying
- Muscarinic receptor agonist
- Urination should occur within 60 minutes
What are the adverse effects of cholinergic agonists
Adverse effects are a result of overstimulation of the PNS
Cardio:
- *Bradycardia, hypotension, AV block and cardiac arrest
GI:
- Cramps, increased secretions, nausea, vomiting
Resp:
- Increased secretions and bronchospasms
CNS:
- Cholinergic receptors are also in the brain
- Headache, dizziness, convulsions
Other:
- Sweating, lacrimation, salivation, loss of binocular accommodation, miosis (pupil constriction)
Drug interactions with cholinergic agonists?
Reduced effects of cholinergic agonists:
- Anticholinergics, antihistamines (1st gen)
Additive effects:
- Other cholinergic agents
What is the antidote for cholinergic stimulation?
Atropine (muscarinic receptor antagonist)
When should the physician be notified (symptoms)?
Muscle weakness, abdominal cramps, diarrhea, or difficulty breathing
Where are cholinergic-blocking drugs primarily used?
In the PNS - only considering the blockers of muscarinic receptors
Some uses in CNS
What’s the difference between anticholinergics, cholinergic blockers, and muscarinic antagonists?
They’re all the same for this class!
