Anticholinergic

Wikipedia, the free encyclopedia - Cite This Source

An anticholinergic agent is a substance that blocks the neurotransmitter acetylcholine in the central and the peripheral nervous system. An example of an anticholinergic is dicyclomine. Generally speaking, it reduces the effects mediated by acetylcholine on acetylcholine receptors in neurons through competitive inhibition. The effect is therefore reversible.

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.

Effects

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 "fun" by experienced recreational drug users, possibly due to the lack of euphoria caused by them. (For some of the "recreational" effects, see the article on 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 the decrease of acetylcholine production associated with age.

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 possibly acceleration of caries
Cessation of perspiration; consequent decreased thermal dissipation through the skin leading to hot, 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)
Urinary retention
Diminished bowel movement, sometimes ileus
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
Short-term memory loss
Inability to concentrate
Wandering thoughts; inability to sustain a train of thought
Incoherent speech
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"

Visual, auditory, or other sensory hallucinations

Warping or waving of surfaces and edges
Textured surfaces
"Dancing" lines; "spiders", insects
Lifelike objects indistinguishable from reality
Hallucinated presence of people not actually there

Rarely: seizures, coma and death

Acute anticholinergic syndrome is completely reversible and subsides once all of the toxin has been excreted. Ordinarily, no specific treatment is indicated. However, in extreme cases, especially those that involves severe distortions of mental state, a reversible cholinergic agent such as physostigmine may be used.

Plant sources

The most common plants containing anticholinergic alkaloids are:

Atropa belladonna (Deadly Nightshade)
Brugmansia species (Brugmansia)
Datura species (Datura)
Hyoscamus 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.

External links

National Library of Medicine - Medical Subject Headings:

Wikipedia, the free encyclopedia © 2001-2006 Wikipedia contributors (Disclaimer)
This article is licensed under the GNU Free Documentation License.
Last updated on Saturday July 19, 2008 at 13:00:52 PDT (GMT -0700)
View this article at Wikipedia.org - Edit this article at Wikipedia.org - Donate to the Wikimedia Foundation