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Anti-muscarinic agents

Muscarinic antagonist

 

 

A muscarinic receptor antagonist (MRA) is a type of anticholinergic agent that blocks the activity of the muscarinic acetylcholine receptor. 

 

 

Anticholinergic agents are is a group of substances that blocks the action of the neurotransmitter acetylcholine (ACh) at synapses in the central and the peripheral nervous system, and, in broad terms, neuromuscular junction.

 

 

Such  agents 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, and many other parts of the body.

 

 

The parasympathetic cholinergic process enhances  ACh function.

 

 

Anticholinergics are divided into two categories in accordance with their specific targets in the central, peripheral nervous system and neuromuscular junction: antimuscarinic agents, and antinicotinic agents which are ganglionic blockers, neuromuscular blockers).

 

 

Anticholinergic drugs are used to treat a variety of conditions:

 

 

Dizziness-vertigo and motion sickness-related symptoms

 

 

Extrapyramidal symptoms

 

 

Gastrointestinal disorders-peptic ulcers, diarrhea, pylorospasm, diverticulitis, ulcerative colitis, nausea, and vomiting?

 

 

Genitourinary disorders-cystitis, urethritis, and prostatitis.

 

 

Insomnia

 

 

Respiratory disorders-asthma, chronic bronchitis, and chronic obstructive pulmonary disease [COPD])

 

 

Sinus bradycardia due to a hypersensitive vagus nerve.

 

 

Anticholinergics generally decrease saliva production, and most produce some level of sedation, both being advantageous for surgery procedures.

 

 

Physiological effects include: 

 

 

delirium

 

 

ocular symptoms–mydriasis, pupil dilation, and acute angle-closure glaucoma in those with shallow anterior chamber. 

 

 

anhidrosis/dry mouth/dry skin

 

 

fever

 

 

constipation

 

 

tachycardia

 

 

urinary retention

 

 

cutaneous vasodilation

 

 

The most significant feature is delirium.

 

 

Long-term use may increase the risk of both cognitive and physical decline.

 

 

Older adults hav an increased  risk of death.

 

 

Possible effects of anticholinergics include:

 

 

Poor coordination

 

 

Dementia

 

 

Decreased mucus production in the nose and throat.

 

 

Dry, sore throat.

 

 

Dry-mouth with possible acceleration of dental caries.

 

 

Cessation of sweating.

 

 

Decreased epidermal thermal dissipation.

 

 

Increased body temperature

 

 

Pupil dilation.

 

 

Photophobia

 

 

Loss of accommodation

 

 

Loss of focusing ability, blurred vision.

 

 

Double-vision

 

 

Increased heart rate

 

 

Tendency to be easily startled

 

 

Urinary retention

 

 

Urinary incontinence while sleeping

 

 

Diminished bowel movements, decreasing  motility via the vagus nerve.

 

 

Increased intraocular pressure; 

 

 

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 

 

 

Wakeful myoclonic jerking

 

 

Unusual sensitivity

 

Visual, auditory, or other sensory hallucinations

 

Warping or waving of surfaces and edges

 

Textured surfaces

 

“Dancing” lines; “spiders”, insects; forts.

 

 

Contraindications to antimuscarinic medication include: narrow angle glaucoma, impaired gastric emptying, and in patients with oral forms of potassium chloride.

 

 

 Relative contraindications include post void residual excess, and impaired or decline in cognitive function.

 

 

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