Flashcards in Anticholinergics Deck (44):
Anticholinergic drugs competitively antagonize the effects of what?
What terms are commonly used interchangeably when blocking the parasympathetic nervous system?
-Antimuscarinic and anticholinergic
-although truly an anticholinergic can have effects at Nicotinic cholinergic sites as well
What drug is a naturally occurring alkaloid of the Belladonna plant or synthetic derivatives?
What drug occurs in Hyoscyamus or “Henbane”?
Antihistamines, antipsychotic and antidepressant drugs may also have what type of effects do to similar structures of anticholinergics?
antimuscarinic effects (anti parasympathetic)
How do anticholinergics cause parasympatholytic effects?
Combine reversibly with muscarinic receptors preventing Ach from activating site
How can anticholinergics effects be overcome or reversed?
increasing Ach concentration = (muscarinic receptor activation= parasympathetic effects "rest and digest")
Where are the effects of muscarinic receptor M1 activation seen?
CNS and stomach
Where are the effects of muscarinic receptor M2 activation seen?
airway smooth muscle, heart, CNS
Where are the effects of muscarinic receptor M3 activation seen?
CNS, glands, airway smooth muscle
Where are the effects of muscarinic receptor M4 activation seen?
Where are the effects of muscarinic receptor M5 activation seen?
Low dose anticholinergics will inhibit which muscarinic receptor?
M3 receptors (glands-bronchial and salivary)
Slightly higher dose anticholinergics will stimulate which muscarinic receptor?
M2 receptors (heart and eye)
High dose anticholinergics will inhibit which muscarinic receptor?
M1 cholinergic control of GI motility and secretion and urination,
Which anticholinergic drugs will produce CNS effects?
-minimal from atropine at normal doses
-none from Glycopyrrolate
What are the CNS effects seen with scopolamine and atropine?
-Sedation (usually first, especially with Scopolamine), followed by stimulation, hallucinations
– Decreases tremor from Parkinson's (decreased dopaminergic activity, relative excess of cholinergic activity)
What is Central Anticholinergic Syndrome (aka postop delirium)?
-Side effects ranging from stupor to excitation and delirium, seizures, coma etc from muscarinic receptor involvement in the brain.
-commonly from atropine toxicity
What drugs/compounds can cause Central Anticholinergic Syndrome?
-Any compound with antimuscarinic effects which cross BBB includes:
– Antipsychotic and antidepressant drugs
– Antiparkinson and antihistamines
– Belladonna alkaloids, tertiary amines, certain plants
What is the anticholinergic effect seen with the eye?
– Reduced lacrimal secretion (dry eyes)
What is mydriasis?
blocking action of pupillary constrictor muscle= dilation
What is cycloplegia?
weakens contraction of ciliary muscle, lost ability to accommodate
What is the anticholinergic effect seen with the cardiovascular system?
Net effect is increased HR, little effect on BP
Why is increased HR seen after giving anticholinergic?
-SA node sensitive to muscarinic blockade
-Atria very innervated by PNS via the vagus
Low doses of Atropine can cause what?
-Initial bradycardia (may be the result of block of presynaptic fibers which normally limit Ach release in the SA node)
Does the parasympathetic nervous system have any innervation on blood vessels?
No but stimulates release of EDRF (endothelium derived relaxing factor)
Release of EDRF (endothelium derived relaxing factor) results in what?
At toxic doses (and in some individuals at normal doses) antimuscarinic drugs can cause?
cutaneous vasodilation, especially in the upper body (mechanism is unclear)
What is the anticholinergic effect seen with the respiratory system?
– Causes bronchdilation and reduced secretions (not as efficient as Beta stimulants)
– Smooth muscle and secretory glands receive vagal stimulation so blocking this results in above
What is the anticholinergic effect seen with the GI system?
-Decreased motility and secretions
–Antisialagogue= decrease saliva
–Less effect on gastric secretions but volume is reduced
What is the anticholinergic effect seen with the GU system?
– Relaxes smooth muscle of ureter and bladder wall, slowed voiding (can cause retention)
– Useful in treating spasms
– No significant uterine effects
What is the anticholinergic effect seen with the sweat glands?
– Suppression of thermoregulatory sweating
– Elevated temp only in large doses or in infants (“atropine fever”)
What are anticholinergics used for pre-op?
– Sedation (rarely)
– Protection from vagal response
Other uses for anticholinergics include:
-Mydriasis for ophthalmology
-Treatment of bradycardia
What are some situations where anticholinergics are used to treat bradycardia?
– From other drugs (volatile agents, narcotic, beta blocker)
– From cardiac pathology
– From anticholinesterase agents
What anticholinergics can be used for motion sickness?
Scopolamine & Dramamine- (thought to block medulla from over stimulation from vestibular apparatus)
What is Ipratropium Atrovent used for?
-Also available as nasal spray for allergic rhinitis
Where is Ipratropium metabolized and excreted?
Metabolized in liver, excreted in feces
Common side effects from Ipratropium (Atrovent)?
cough, headache, dry mouth, palpitations, nausea, etc.
What is the structure of atropine and what does this allow for or prevent?
-lipid soluble, allows it to cross BBB
Small doses of anticholinergics, most particularly Atropine, may result in what?
decreased heart rate (<0.1mg pediatrics)
What the physiology of the bradycardia seen with low doses of atropine?
-Thought to be the result of block of presynaptic inhibitory M1 receptors (from more affinity in low doses) on vagal nerve endings which normally provide negative feedback to stop further ACH release.
-The lack of negative feedback mechanism results in more ACH which overcomes the sinoatrial, M2 blockade from the low dose
What is the structure of Scopolamine and what does this allow for or prevent?
• Tertiary amine, lipid soluble
• Readily crosses BBB