Cholinergic Drugs (aka parasympathetic drugs)
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:
Smooth muscle of GI tract and Bladder
Pupilary constriction (myosis)
Used to treat Glaucoma. Rx given as an eye drop.
: 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.
Stimulates secretions to keep mucus membranes moist
Upper respiratory 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 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
: 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
Usually given SQ for effects on Urinary tract- used rarely
Adverse reactions of cholinomimetics
Potential life threatening reactions
excessive mucus production
Should have Atropine (epinephrine) available
Muscarinic receptor Antagonist
Bind to muscarinic receptors…but produce no effects
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
: When taken by inhalation very little is absorbed systemically-local effect is significant. PE is sedation.
: 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
: Dry mouth
: Decreases gastric motility.
: blurred vision
Increased body temperature due to lack of sweating.
: 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.
Causes constriction by keeping acetylcholine at receptors
Will cause myosis (irreversible but not permanant action)
Increased mucous production
Treatment of Alzheimer’s Disease
Allows for brain function because acetylcholine is acting in the at the cranial synapses.
Adverse rxn of Acetylcholinesterase Inhibitors
Overactivity at muscarinic receptors like:
Failure of transmission at nicotinic receptors
muscle fasciculation (twitching)
Toxicity and Treatment of toxicity
Chapter on Parasympathetic Nervous System