Anhidrosis
a deficiency or absence of sweat
Anticholinergic drugs
Subtypes: muscarinic, nicotinicN, and nicotinicM
Belladonna Alkaloids
examples: atropine, hyoscyamine, and scopolamine
Cholinergic durgs
agents that influence the activity of cholinergic receptors. Most of these drugs act directly at cholinergic receptors, where they either mimic or block the actions of acetylcholine.
Muscarinic Agonist
bind to muscarinic receptors and thereby cause receptor activation. Since nearly all muscarinic receptors are associated with the parasympathetic nervous system, responses to muscarinic agonists closely resemble those produced by stimulation of parasympathetic nerves. Accordingly, muscarinic agonists are also known as parasympathomimetic agents. (Bethanechol)
Muscarinic Antagonist
competitively block the actions of acetylcholine at muscarinic receptors. Because the majority of muscarinic receptors are located on structures innervated by parasympathetic nerves, the muscarinic antagonists are also known as parasympatholytic drugs. Additional names for these agents are antimuscarinic drugs, muscarinic blockers, and anticholinergic drugs. (Atropine)
Parasympatholytic Drugs
muscarinic antagonists
Parasympathomimetic Agents
muscarinic agonists
Xerostomia
dry mouth
OAB
Overactive bladder akaurgency incontinence, detrusor instability, and sometimes “can’t-hold-it-anymore” incontinence. four major symptoms: urinary urgency, nocturia, Urinary frequency, urge incontinence.
M1 Receptor Location
Salivary glands and CNS (brain)
M1 Receptor Activation Response
salivation and enhanced cognition
M1 Receptor Blockade Response
dry mouth, Confusion, hallucinations
M2 Receptor Location
Heart
M2 Receptor Activation Response
Bradycardia
M2 Receptor Blockade Response
Tachycardia
M3 Receptor Location
- Salivary glands,
- Bladder: detrusor,
- GI smooth muscle
- Eyes: Iris sphincter,
- Eyes: Ciliary muscle,
- Eyes: Lacrimal gland.
M3 Receptor Activation Response
- Salivation,
- Bladder Contraction of detrusor (increased pressure),
- GI: Increased smooth muscle tone and motility,
- Eye: Puple constriction, Ciliarry muscle contraction (Vision - accommodation), Tearing
M3 Receptor Blockade Response
- Dry mouth,
- Bladder Relaxation (decreased pressure),
- Decreased GI tone and motility (constipation),
- Eye: Relaxation of Iris sphincter (mydriasis), Relaxation of ciliary muscle (blurred vision), Dry eyes
Atropine Category
muscarinic antagonist
Atropine Use
Pre-anesthesia medication (help stimulate baroreceptors during surgery),
- Disorders of the eye
- Bradycardia
- Diverticulitis (Intestinal hypertonicity and hypermotility)
- Muscarinic agonist poisoning
- Peptic ulcer disease
- Asthma
- Biliary colic
Atropine mechanism of action
Atropine produces its effects through competitive blockade at muscarinic receptors. Like all other receptor antagonists, atropine has no direct effects of its own.
Atropine adverse effects
- Xerostomia (dry mouth)
- Blurred vision and photophobia
- Elevation of intraocular pressure
- Urinary retention
- Constipation
- Anhidrosis
- Tachycardia
- Asthma (it can cause thickening of secretions)
Darifenacin Category
anticholinergic agents
Darifenacin Use
treatment of OAB while having no effect on M1 receptors in the brain or M2 receptors in the heart
Darifenacin Mechanism of action
M3 selectivity anticholinergic agent.
Darifenacin adverse effects
- Dry mouth (most common)
- Constipation is also common.
- Others include dyspepsia (indigestion), gastritis, and headache.
Bethanechol Category
muscarinic agonists
Bethanechol Use
Urinary retention and investigational GI uses
Bethanechol Mechanism of action
The drug binds reversibly to muscarinic cholinergic receptors to cause activation. At therapeutic doses, bethanechol acts selectively at muscarinic receptors, having little or no effect on nicotinic receptors, either in ganglia or in skeletal muscle.
Bethanechol adverse effects
- Cardiovascular system: Hypotension
- Gastrointestinal system: Increased tone and motility
- Exacerbation of asthma
- Dysrhythmias in patients with hyperthyroidism (MEMORIZE) - Because patients with hyperthyroidism are sensitive to sympathetic activation of beta1 receptors (baroreceptor reflex)
Muscarinic Receptors Location
-Heart: Bradycardia
-Exocrine glands: Increased sweating, salivation, bronchial secretions, and secretion of gastric acid
-Smooth muscles
>Contraction in lung (constriction)
>Gastrointestinal tract (increased tone/motility)
>Bladder (contraction of detrusor & relaxation of trigon and sphincter)
>Vascular (relaxation, vasodilation, and hypotension)
>Eye (pupillary constriction and ciliary contraction)
NicotinicN Receptors Location
All ganglia of the autonomic nervous system
NicotinicM Receptors Location
Neuromuscular junctions (NMJs)
Muscarinic Receptors Effects
Many, including:
↓ Heart rate
↑ Gland secretion
Smooth muscle contraction
NicotinicN Receptors Effects
Promotes ganglionic transmission
NicotinicN Receptors Effects
Skeletal muscle contraction
Toxicology of Muscarinic Antagonists
Symptoms include:
- Dry mouth
- Blurred vision
- Photophobia
- Hyperthermia
- Central nervous system effects
- Hot, dry, and flushed skin