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Cholinergic Drugs (aka parasympathetic drugs)
- Acytlcholine-->muscarinic receptors
- Achieve effects through stimulation and inhibition of muscarinic cholinergic receptors.
All meds are either going to be agonists or antagonists.
Cholinergic Drugs will affect
- Organs and/or Systems affected:
- Exocrine glands
- Smooth muscle of GI tract and Bladder
- Blood vessels
- Pupilary constriction (myosis)
- Used to treat Glaucoma. Rx given as an eye drop.
- Glaucoma: increased occular pressure due to lack of occular fluid circulation. Constriction of the pupil stimulates occular fluid circulation and releaves the pressure.
Cholinergic Drug effects on the Exocrine glands and smooth muscle of the GI and bladder.
- Exocrine Glands
- Stimulates secretions to keep mucus membranes moist
- Upper respiratory tract
- GI tract
- Activation of sweat glands
- Avoid giving to pt with airway problems like aesthma, COPD, etc.
- Smooth muscle of GI tract and Bladder
- Increase Tone and motility
- Increase Defacation
- Increase urge to Voiding
Cholinergic Rx effects on Airways and heart
- Increased secretion of mucous
- Vagus Nerve activity--> slows heart rate and conduction through the AV node
- Do not give to someone with heart block or bradycardia
Cholinergic Rx effects on Blood Vessels
- Parasympathetic nerves are not generally found on blood vessels
- However….muscarinic receptors are found on all vessels
- Stimulation results in:
- Relaxed vascular smooth muscle
- Used to reduce BP.
Muscarinic Receptor Agonist
- Action (Cholinomimetic): Will intensify action of aceytlcholine
- Mimic the action of acetycholine
- Pilocarpine - Treatment of glaucoma - causes miosis
- Bethanechol - Treatment of urinary retention or to stimulate GI motillity
Muscarinic receptor agonist cholinomimetics
- Poorly absorbed if given orally
- Will have local effect on GI tract
- Eye drops
- Usually given SQ for effects on Urinary tract- used rarely
Adverse reactions of cholinomimetics
Should have Atropine (epinephrine) available
- Potential life threatening reactions
- excessive mucus production
Muscarinic receptor Antagonist
- Bind to muscarinic receptors…but produce no effects
- Other terms:
- Atropine - Causes mydriasis (pupilary dialation) and cycloplegis (blurred vision) because pupils will not be able to focus.
- Glycopyrrolate (Robinul) - Inhibits bronchial and salivary secretions--decreases aspiration during surgery
- Ipratropium (Atrovent) Blocks contraction of bronchial smooth muscle. Inhaler for aesthma.
- Oxybutynin (Ditropan) Tolterodine (Detrol) -Used to control overactive bladder reflexes by antagonizing receptors.
Muscarinic Receptor Antagonists Pharmacokinetics
- Ipratropium (Atrovent): When taken by inhalation very little is absorbed systemically-local effect is significant. PE is sedation.
- Scopalamine: Very lipid soluable - crosses blood-brain barrier-effective for treatment of motion sickness
- so lipid soluable it can be absorbed through the skin
Adverse rxn to all anticholinergics
- Xerostomia: Dry mouth
- Constipation: Decreases gastric motility.
- Urinary retention
- Mydriasis: blurred vision
- Increased body temperature due to lack of sweating.
- Glaucoma: will make it worse when pupils dialate.
- Cardiac rhythm disturbances because HR will increase.
- Prevents the degradation of synaptically released acetylcholine
- Therefore--acetylcholine remains in the synapse longer and produces a greater effect
Who needs an acetylcholinesterase inhibitor?
- Treatment of Myasthenia Gravis
- Functional cholinergic nicotinic receptors at the neuromuscular junction have been lost, so acetylcholine stay in these receptors longer to stimulate the ones that are left.
- Will see:
- Diaphram dysfunction
- Causes constriction by keeping acetylcholine at receptors
- OrganophosphatesWill cause myosis (irreversible but not permanant action)
- Increased mucous production
- Respiratory problems
- Treatment of Alzheimer’s DiseaseAllows for brain function because acetylcholine is acting in the at the cranial synapses.
Adverse rxn of Acetylcholinesterase Inhibitors
- Overactivity at muscarinic receptors like:
- increased salivation
- Failure of transmission at nicotinic receptors
- muscle fasciculation (twitching)
Toxicity and Treatment of toxicity
- Respiratory failure
- cardiovascular collapse