Anticholinergic Drugs

What is Antimuscarinic agents / anticholinergic drugs? Their actions , uses and side effects


Anticholinergic Drugs

Commonly called anticholinergic tablets, those retailers (for example, atropine and scopolamine) block muscarinic receptors inflicting inhibition of muscarinic functions. In addition, those tablets block the few extremely good sympathetic neurons which are cholinergic, consisting of the ones innervating the salivary and sweat glands. 

Because they do now no longer block nicotinic receptors, the anticholinergic tablets (greater precisely, antimuscarinic tablets) have very little movement at skeletal neuromuscular junctions (NMJs) or autonomic ganglia. 

The anticholinergic tablets are useful in numerous scientific situations. [Note: A number of antihistamines and antidepressants (mainly tricyclic antidepressants) also have antimuscarinic activity.]


Atropine is a tertiary amine belladonna alkaloid with a excessive affinity for muscarinic receptors. It binds competitively and forestalls ACH from binding to the ones sites .Atropine acts each centrally and peripherally. 

Its trendy moves ultimate approximately four hours, besides while located topically within side the eye, wherein the movement might also additionally ultimate for days. Neuroeffector organs have various sensitivity to atropine. The finest inhibitory results are on bronchial tissue and the secretion of sweat and saliva .


a. Eye: 

Atropine blocks muscarinic interest within side the eye, ensuing in mydriasis (dilation of the pupil), unresponsiveness to light, and cycloplegia (incapability to recognition for close to vision). In sufferers with angle-closure glaucoma, intraocular stress might also additionally upward thrust dangerously.

b. Gastrointestinal (GI): 

Atropine (because the energetic isomer, L-hyoscyamine) may be used as an antispasmodic to lessen interest of the GI tract. Atropine and scopolamine (mentioned below) are probable the maximum amazing antispasmodic tablets avail able. Although gastric motility is reduced, hydrochloric acid manufacturing isn't always extensively affected. 

Thus, atropine isn't always powerful for the remedy of peptic ulcer. [Note: Pirenzepine, an M, muscarinic antagonist, does reduce gastric acid secretion at doses that do not antagonize other systems.] Doses of atropine that lessen spasms additionally lessen saliva secretion, ocular accommodation, and urination. These results lower compliance with atropine.

c. Cardiovascular

Atropine produces divergent results at the cardiovascular system, relying at the dose . At low doses, the major impact is a moderate lower in coronary heart charge. This impact effects from blockade of the M, receptors at the inhibitory prejunctional (or presynaptic) neurons, accordingly allow ting multiplied ACh release. Higher doses of atropine motive a modern boom in coronary heart charge via way of means of blocking off the M, receptors at the sinoatrial node.

d. Secretions: 

Atropine blocks muscarinic receptors within side the salivary glands, generating dryness of the mouth (xerostomia). The salivary glands are exquisitely touchy to atropine. Sweat and lacrimal glands are in addition affected. (Note: Inhibition of secretions via way of means of sweat glands can motive multiplied frame temperature, which may be risky in kids and the elderly.]

Therapeutic uses:

a. Ophthalmic

Topical atropine exerts each mydriatic and cycloplegic results, and it allows the size of refractive mistakes with out interference via way of means of the accommodative ability of the eye. Shorter-performing antimuscarinics (cyclopentolate and tropicamide) have in large part changed atropine because of extended mydriasis found with atropine (7 to fourteen days vs. 6 to 24 hours with different retailers). 

[Note: Phenylephrine or similar a-adrenergic drugs are preferred for pupillary dilation if cycloplegia is not required.]

b. Antispasmodic

Atropine is used as an antispasmodic agent to loosen up the GI tract.

c. Cardiovascular

The drug is used to deal with bradycardia of various etiologies.

d. Antisecretory

Atropine is on occasion used as an ant secretory agent to dam secretions within side the higher and decrease respiration tracts previous to surgery.

e. Antidote for cholinergic agonists

Atropine is used for the remedy of organophosphate (insecticides, nerve gases) poisoning, of overdose of clinically used anticholinesterases consisting of physostigmine, and in a few styles of mushroom poisoning (sure mushrooms incorporate cholinergic materials that block cholinesterase's). 

Massive doses of atropine can be required over a protracted time period to counteract the poisons. The capacity of atropine to go into the significant frightened system (CNS) is of specific significance in treating significant poisonous results of anticholinesterases.


Atropine is with no trouble absorbed, partly metabolized via way of means of the liver, and removed in general in urine. It has a half-lifestyles of approximately four hours.

Adverse results: 

Depending at the dose, atropine might also additionally motive dry mouth, blurred vision, "sandy eyes, tachycardia, urinary retention, and constipation. Effects at the CNS encompass stressed ness, confusion, hallucinations, and delirium, which might also additionally progress to depression, crumble of the circulatory and respiration systems, and death. 

Low doses of cholinesterase inhibitors, consisting of physostigmine, can be used to triumph over atropine toxicity Atropine may set off tough urinary retention. The drug can be risky in kids, due to the fact they may be touchy to its results, specifically to fast will increase in frame temperature that it can elicit.


Scopolamine any other tertiary amine plant alkaloid, produces peripheral results just like the ones of atropine. However, scopolamine has more movement at the CNS (not like atropine, CNS results are found at healing doses) and an extended period of movement compared to atropine. It has a few unique moves as indicated below.


Scopolamine is one of the only anti-movement illness tablets to be had . It additionally has the uncommon impact of blocking off short-time period memory. In comparison to atropine, scopolamine produces sedation, however at better doses, it may produce excitement. Scopolamine might also additionally produce euphoria and is prone to abuse.

Therapeutic uses

The healing use of scopolamine is restricted to prevention of movement illness and postoperative nausea and vomiting. For movement illness, it's far to be had as a topical patch that gives results for up to a few days. [Note: As with all drugs used for motion sickness, it is much more effective prophylactically than for treating motion sickness once it occurs.]

Pharmacokinetics and unfavorable results: 

These elements are just like the ones of atropine.

Ipratropium and tiotropium: 

Ipratropium and tiotropium are quaternary derivatives of atropine. These retailers are permitted as bronchodilators for protection remedy of bronchospasm related to persistent obstructive pulmonary ailment (COPD). Ipratropium is likewise utilized in the intense control of bronchospasm in asthma. 

Both retailers are introduced thru inhalation Because in their fine charges, those tablets do now no longer input the systemic circulate or the CNS, separating their results to the pulmonary system. Tiotropium is run as soon as daily, a main benefit over ipratropium, which calls for dosing as much as 4 instances daily.

Tropicamide and cyclopentolate

These retailers are used as ophthalmic answers for mydriasis and cycloplegia. Their period of movement is shorter than that of atropine. Tropicamide produces mydriasis for six hours and cyclopentolate for twenty-four hours.

Benztropine and trihexyphenidyl: 

Benztropine and trihexyphenidyl are beneficial as adjuncts with different antiparkinsonian retailers to deal with Parkinson's ailment and different styles of parkinsonian syndromes, consisting of antipsychotic brought on extrapyramidal symptoms.

Darifenacin, fesoterodine, oxybutynin, solifenacin, tolterodine, and trospium chloride: 

These artificial atropine-like tablets are used to deal with overactive bladder. By blocking off muscarinic receptors within side the bladder, intravesical stress is lowered, bladder ability is multiplied, and the frequency of bladder contractions is reduced. Side results encompass dry mouth, constipation, and blurred vision, which restrict tolerability of those retailers if used continually. 

Oxybutynin is to be had as a trans dermal system (topical patch), that is higher tolerated as it reasons much less dry mouth than oral formulations. The normal efficacies of those antimuscarinic tablets are similar.

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