Direct Acting Cholinergic Agonists Overview

Drugs that mimic the actions of acetylcholine (Ach) in the body.

Cholinomimetics that directly stimulate acetylcholine receptors, similar to how acetylcholine itself does.

A group of direct-acting cholinomimetics including acetylcholine, carbachol, methacholine, and bethanechol.

Choline esters are generally poorly absorbed from the gut and have limited ability to cross the blood-brain barrier.

Acetylcholine is rapidly broken down by cholinesterase, leading to a short duration of action.

Methacholine has a longer duration of action than acetylcholine because it is less susceptible to breakdown by cholinesterase.

Carbachol is a choline ester with a negligible effect on cholinesterase, giving it a longer duration of action.

Bethanechol, a choline ester, is minimally affected by cholinesterase, resulting in a prolonged effect.

Bethanechol primarily targets the bladder and bowels, showing reduced effects on the cardiovascular system.

Methacholine can be administered orally and is more resistant to breakdown by cholinesterase than acetylcholine, resulting in a longer duration of action.

A group of direct-acting cholinomimetics that include muscarine, nicotine, lobeline, pilocarpine, arecholine, and oxotremorine.

Muscarine, a quaternary amine, is found in poisonous mushrooms and primarily acts on muscarinic receptors.

Nicotine, lobeline, and pilocarpine are examples of tertiary alkaloids, well absorbed from the gut.

Nicotine, a lipophilic liquid found in tobacco, can be absorbed through the skin.

Acetylcholine slows down the heart rate (negative chronotropy), reduces its contractility (negative inotropy), and decreases conduction velocity through the atrioventricular node (negative dromotropy).

Acetylcholine causes bronchoconstriction by contracting bronchial muscle and increases bronchial secretions.

Acetylcholine increases gut motility, relaxes sphincters, and stimulates secretions, leading to bowel evacuation.

Acetylcholine causes contraction of the detrusor muscle, relaxation of the trigone and sphincter, and increased peristalsis in the ureter, stimulating urination.

Acetylcholine increases secretions from sweat, salivary, lacrimal, and nasopharyngeal glands.

Acetylcholine causes constriction of the sphincter muscle of the iris (miosis) and contraction of the ciliary muscle for near vision.

Acetylcholine stimulates contraction of skeletal muscles at the motor endplate.

Bethanechol is used to treat conditions like postoperative ileus, urinary retention, and neurogenic bladder atony.

Pilocarpine and cevimeline are used to treat dry mouth, a symptom of Sjogren's syndrome.

Methacholine is used to diagnose bronchial airway hyperreactivity, a characteristic of asthma.

Excessive salivation, sweating, nausea, diarrhea, abdominal cramps, urinary urgency, vasodilation, bronchoconstriction, and hypotension are common adverse effects of cholinomimetics.

Atropine, an anticholinergic drug, is used to treat mushroom poisoning, which involves excessive muscarinic stimulation.

Cholinomimetics are contraindicated in patients with bronchial asthma, GI or urinary tract obstruction.