Anticholinergic An anticholinergic agent is a substance that
blocks the neurotransmitter acetylcholine in the central and the peripheral nervous
system.
Anticholinergics inhibit parasympathetic nerve impulses by selectively blocking the binding
of the neurotransmitter acetylcholine to its receptor in nerve cells.
The nerve fibers of the parasympathetic system are responsible for the involuntary movement
of smooth muscles present in the gastrointestinal tract, urinary tract, lungs, etc.
Anticholinergics are divided into three categories in accordance with their specific targets
in the central and/or peripheral nervous system: antimuscarinic agents, ganglionic blockers,
and neuromuscular blockers.
Pharmacology Anticholinergics are classified according
to the receptors that are affected: Antimuscarinic agents operate on the muscarinic
acetylcholine receptors.
The majority of anticholinergic drugs are antimuscarinics.
Antinicotinic agents operate on the nicotinic acetylcholine receptors.
The majority of these are non-depolarising skeletal muscle relaxants for surgical use
that are structurally related to curare.
Several are depolarizing agents.
Examples Examples of common anticholinergics:
Anti-Muscarinic agents
Atropine Benztropine (Cogentin)
Biperiden Chlorpheniramine (Chlor-Trimeton)
Dicyclomine (Dicycloverine) Dimenhydrinate (Dramamine)
Diphenhydramine (Benadryl, Sominex, Advil PM, etc.)
Doxylamine (Unisom) Glycopyrrolate (Robinul)
Ipratropium (Atrovent) Orphenadrine
Oxitropium (Oxivent) Oxybutynin (Ditropan, Driptane, Lyrinel XL)
Tolterodine (Detrol, Detrusitol) Tiotropium (Spiriva)
Trihexyphenidyl Scopolamine
Solifenacin Tropicamide
Atropine Benztropine (Cogentin)
Biperiden Chlorpheniramine (Chlor-Trimeton)
Dicyclomine (Dicycloverine) Dimenhydrinate (Dramamine)
Diphenhydramine (Benadryl, Sominex, Advil PM, etc.)
Doxylamine (Unisom) Glycopyrrolate (Robinul)
Ipratropium (Atrovent) Orphenadrine
Oxitropium (Oxivent) Oxybutynin (Ditropan, Driptane, Lyrinel XL)
Tolterodine (Detrol, Detrusitol) Tiotropium (Spiriva)
Trihexyphenidyl Scopolamine
Solifenacin Tropicamide
Anti-Nicotinic agents
Bupropion (Zyban, Wellbutrin) - Ganglion blocker Dextromethorphan - Cough suppressant and ganglion
blocker Doxacurium - Nondeplorizing skeletal muscular
relaxant Hexamethonium - Ganglion blocker
Mecamylamine - Ganglion blocker and occasional smoking cessation aid
Tubocurarine - Nondepolarizing skeletal muscular relaxant
Bupropion (Zyban, Wellbutrin) - Ganglion blocker Dextromethorphan - Cough suppressant and ganglion
blocker Doxacurium - Nondeplorizing skeletal muscular
relaxant Hexamethonium - Ganglion blocker
Mecamylamine - Ganglion blocker and occasional smoking cessation aid
Tubocurarine - Nondepolarizing skeletal muscular relaxant
Plants of the Solanaceae family contain various anticholinergic tropane alkaloids such as
scopolamine, atropine, and hyoscyamine.
Physostigmine is one of only a few drugs that can be used as an antidote for anticholinergic
poisoning.
Nicotine also counteracts anticholinergics by activating nicotinic acetylcholine receptors.
Caffeine (although an adenosine receptor antagonist) would counteract the anticholinergic symptoms
by reducing sedation and increase acetylcholine activity, thereby causing alertness and arousal.
Medical and recreational uses Anticholinergic drugs are used in treating
a variety of conditions: Gastrointestinal disorders (e.g., gastritis,
diarrhea, pylorospasm, diverticulitis, ulcerative colitis, nausea, and vomiting)
Genitourinary disorders (e.g., cystitis, urethritis, and prostatitis)
Respiratory disorders (e.g., asthma, chronic bronchitis, and chronic obstructive pulmonary
disease ) Sinus bradycardia due to a hypersensitive
vagus nerve.
Insomnia, although usually only on a short term basis.
Dizziness (including vertigo and motion sickness-related symptoms)
Anticholinergics generally have antisialagogue effects (decreasing saliva production), and
most have at least some sedative effect, both being advantageous in surgical procedures.
When a significant amount of an anticholinergic is taken into the body, a toxic reaction known
as acute anticholinergic syndrome may result.
This may happen accidentally or intentionally as a consequence of recreational drug use.
Anticholinergic drugs are usually considered the least enjoyable by many recreational drug
users, possibly due to the lack of euphoria caused by them.
In terms of recreational use, these drugs are commonly referred to as deliriants.
Because most users do not enjoy the experience, they do not use it again, or do so very rarely.
The risk of addiction is low in the anticholinergic class.
The effects are usually more pronounced in the elderly, due to natural reduction of acetylcholine
production associated with age.
Exceptions to the above include scopolamine, orphenadrine, dicycloverine/dicyclomine and
first-generation antihistamines with central nervous system penetration.
Acute Anticholinergic Syndrome Possible effects of anticholinergics include:
Ataxia; loss of coordination Decreased mucus production in the nose and
throat; consequent dry, sore throat Xerostomia or dry-mouth with possible acceleration
of dental caries Cessation of perspiration; consequent decreased
epidermal thermal dissipation leading to warm, blotchy, or red skin
Increased body temperature Pupil dilation (mydriasis); consequent sensitivity
to bright light (photophobia) Loss of accommodation (loss of focusing ability,
blurred vision – cycloplegia) Double-vision (diplopia)
Increased heart rate (tachycardia) Tendency to be easily startled
Urinary retention Diminished bowel movement, sometimes ileus
(decreases motility via the vagus nerve) Increased intraocular pressure; dangerous
for people with narrow-angle glaucoma Shaking
Possible effects in the central nervous system resemble those associated with delirium, and
may include: Confusion
Disorientation Agitation
Euphoria or dysphoria Respiratory depression
Memory problems Inability to concentrate
Wandering thoughts; inability to sustain a train of thought
Incoherent speech Irritability
Mental confusion (brain fog) Wakeful myoclonic jerking
Unusual sensitivity to sudden sounds Illogical thinking
Photophobia Visual disturbances
Periodic flashes of light Periodic changes in visual field
Visual snow Restricted or "tunnel vision"
Periodic flashes of light Periodic changes in visual field
Visual snow Restricted or "tunnel vision"
Visual, auditory, or other sensory hallucinations
Warping or waving of surfaces and edges Textured surfaces
"Dancing" lines; "spiders", insects; form constants
Lifelike objects indistinguishable from reality Phantom smoking
Hallucinated presence of people not actually there
Warping or waving of surfaces and edges Textured surfaces
"Dancing" lines; "spiders", insects; form constants
Lifelike objects indistinguishable from reality Phantom smoking
Hallucinated presence of people not actually there
Rarely: seizures, coma, and death Orthostatic hypotension (sudden dropping of
systolic blood pressure when standing up suddenly) and significantly increased risk of falls
in the elderly population.
A common mnemonic for the main features of anticholinergic syndrome is the following:
Hot as a hare (hyperthermia) Blind as a bat (dilated pupils)
Dry as a bone (dry skin) Red as a beet (vasodilation)
Mad as a hatter (hallucinations/agitation) The bowel and bladder lose their tone and
the heart goes on alone (ileus, urinary retention, tachycardia)
Remedies Acute anticholinergic syndrome is completely
reversible and subsides once all of the causative agent has been excreted.
Reversible cholinergic agents such as physostigmine can be used in life-threatening cases.
Wider use is discouraged due to the significant side effects, such as rapid heart beat and
decreased blood pressure.
Piracetam (and other racetams), α-GPC and choline are known to activate the cholinergic
system and alleviate cognitive symptoms caused by extended use of anticholinergic drugs.
Plant sources The most common plants containing anticholinergic
alkaloids are: Atropa belladonna (Deadly Nightshade), source
of atropine Brugmansia species (Brugmansia)
Datura species (Datura) Hyoscyamus niger (Henbane)
Mandragora officinarum (Mandrake) Use as a deterrent
Certain preparations of some drugs, such as hydrocodone, are mixed with an anticholinergic
agent to deter intentional overdose.