Anticholinergic agent

Anticholinergic agents are a group of pharmacological substances that block the action of the neurotransmitter acetylcholine in the central nervous system and the peripheral nervous system. These agents inhibit the transmission of parasympathetic nerve impulses, thereby reducing spasms of smooth muscles (e.g., in the bladder, intestines, and airways), increasing heart rate, dilating the pupils, and decreasing bodily secretions such as saliva, sweat, and mucus.

Mechanism of Action

Anticholinergic agents work by competitively inhibiting the action of acetylcholine at muscarinic receptors, which are a subtype of acetylcholine receptors. This inhibition can occur at various sites within the body, including the eye, heart, smooth muscles, and exocrine glands, leading to a wide range of effects. These effects are often summarized by the mnemonic "dry as a bone, red as a beet, blind as a bat, mad as a hatter, and hot as a hare," which describes the symptoms of anticholinergic toxicity.

Clinical Uses

Anticholinergic agents have diverse clinical applications. They are used in the treatment of:

• Asthma and COPD (Chronic Obstructive Pulmonary Disease) to dilate the airways
• Irritable Bowel Syndrome (IBS) and gastrointestinal spasms to reduce smooth muscle spasms
• Parkinson's disease to reduce muscle rigidity and tremors
• Overactive bladder to reduce urinary urgency
• Motion sickness and certain types of nausea
• Preoperative use to reduce saliva and respiratory secretions

Side Effects

The use of anticholinergic agents can lead to several side effects due to their broad mechanism of action. Common side effects include:

• Dry mouth
• Blurred vision
• Constipation
• Urinary retention
• Confusion, especially in the elderly
• Increased heart rate

Examples of Anticholinergic Agents

Some common anticholinergic drugs include:

• Atropine
• Scopolamine
• Ipratropium
• Tiotropium
• Oxybutynin
• Tolterodine

Risks and Precautions

Long-term use of anticholinergic agents, especially in the elderly, has been associated with an increased risk of cognitive decline and dementia. Therefore, these drugs should be used with caution in older adults and those with pre-existing cognitive impairments.

See Also

• Cholinergic antagonist
• Neurotransmitter
• Pharmacology
• Muscarinic receptor