CHOLINERGIC BLOCKING AGENTS

Classification

1.       Solanaceous alkaloid ---- atropine sulphate, homatropine hydrobromide, ipratropium bromide

2.       Synthetic cholinergic blocking aent

·         Amino alcohol ester --- clinidium bromide, dicyclomine hydrochloride, cyclopentolate          hydrochloride, glycopyrrolate, propantheline bromide

·         Amino alcohol ethers --- benzotropine mesylate, orphenadrine citrate

·         Amino alcohol ------------ biperidine, procyclidine

·         Amino amide ------------- tropicamide

·         Miscellaneous ------------ ethopropazine

Synthetic cholinergic blocking agents

MECHANISM

The most potent anticholinergic drugs are derived from muscarinic agonists that contain one or sometimes two large or bulky groups.

effects of ACh. 1. Mydriatic effect: dilation of the pupil of the eye; and cycloplegia, a paralysis of the ciliary structure of the eye, resulting in a paralysis of accommodation for near vision 2. Antispasmodic effect: lowered tone and motility of the GI tract and the genitourinary tract 3. Antisecretory effect: reduced salivation (antisialagogue), reduced perspiration (anhidrotic), and reduced acid and gastric secretion

the most common side effects experienced from the oral use of these drugs, under ordinary conditions, are dryness of the mouth, mydriasis, and urinary retention.

Anticholinergic drugs have a minor role in the management of peptic ulcer disease

be a combination of a nonirritating diet to reduce acid secretion, antacid therapy, and reduction of emotional stress. Most of the anticholinergic drugs are offered either as the chemical alone, or in combination with a CNS depressant such as phenobarbital, or with a neuroleptic drug to reduce the CNS contribution to parasympathetic hyperactivity. In addition to the antisecretory effects of anticholinergics on hydrochloric acid and gastric acid secretion, there have been some efforts to use them as antisialagogues and anhidrotics.

The principal goal of anticholinergic drugs in the treatment of parkinsonism is to decrease the activity of cholinergic neurons in the basal ganglia.

Solanaceous alkaloid

These are the ester of tropine and tropic acid, these alkaloids are inhibitors of parasympathetic nervous system and stimulators of center of nervous system.

Atropine is a racemic mixture.

hyosyamine is the levorotatary isomer of atropine.

Hyoscine is an ester of tropic acid and scopine.

Solanaceous alkaloid has a basic piperidine ring. exist in both chair and boat form.

Presence of tropine end tropic acid ester and free oh group is essential for activity

These also have antispasmodic activity on smooth muscles

Atropine sulphate

It has both central and peripheral action.it first stimulates and depress cns. antispasmodic action.it reduces tone of smooth muscle and diminishes the gastric and intestinal motility.

In duodenal and gastric ulcer

Treatment of smooth muscle spasm

In symptomatic treatment of parkinsonism

in general aneasteshia to reduce brochial and salivary secretion

it also have cycloplegia and mydriatic action

Homatropine hydrobromide

It is an ester of mandelic acid with tropine

homatropine

topically used as mydriatric and cyclopegic

Ipratropium bromide

It is an quanternary ammonium compound which blocks muscarinic acetyl choline recepetors.it is non selective muscarinic antagonist.

Uses

ipratropium

inhalation usd  for COPD and asthma

nasal solution for rhinorrhea

in combination with beta adrenergic .increases dilating effect of bronchi

synthetic cholinergic blocking agent

Efforts at synthesis started with rather minor deviations from the atropine molecule, but a review of the commonly used drugs today indicates a marked departure from the rigid tropane aminoalcohols and tropic acid residues

tropicamide

competitive antagonism to acetyl choline

uses

antimuscarinic drug,short acting mydriatic ,cycloplegia

eye drops are often used to treat anterior uveitis

used with other sympathomimetic agents to dilate the iris muscle

cyclopentolate hydrochloride

it is competitive antagonist. It binds to the receptor in place of acetyl choline and reverse its action.it act more quickly than atropine and has shorter duration of action.

Uses

Eye drop to produce cycloplegia and mydriasis

Clinidium bromide

It binds to muscarinic acetyl choline receptors present on smooth muscle and secretory glands and finally inhibit the receptors.it relaxes smooth  uscle and decreases biliary tract infection

Uses

Antispasmodic and antiulcer.

Treatment of irrirtable bowel syndrome

In electrocolitis

Dicyclomine hydrochloride

Non selective smooth muscle relaxant.specific anticholinergic effect at muscarinic receptors

Uses

In treatment of irritable bowel syndrome

Used as adjunct in the treatment of gastric and duodenal ulcer

Glycopyrrolate

Block muscarinic receptors

Use

Before surgery to reduce secretion

With neostigmine reduce bradycardia(muscarinic effect)

In gastric ulcer to reduce acid secretion

Inhalation to trat COPD

Propatheline bromide

Binding to muscarinic receptors

Uses

In spasm of stomach,intestine .bladder

In excessive sweting

Combination with antacid in gastric ulcer

Benzotropne mesylate

Anticholinergic or antihistamine agents.selective M1muscarinic antagonist

Uses

In parkinsonism

Antihistamic and local anaesthetic activity

In dystonia

Orphenadrine citrate

Non selective ach receptor antagonist and also H1 receptor antagonist

Uses

Releve pain due to spasam of voluntary muscle

In parkinsonism disease

In rheumatoid pain

Biperidine hydrochloride

Centrally blocking M1receptors.

Uses

Parkinsonison disease

Rleive sode effects of antopsychotic drugs

Relieve muscle rigidity sand abnormal sweating and salivation

Procyclidine hydrochloride

Blocks muscarinic receptor

Use

In drug induced parkinsonism

In akathisia and dystonia

Ethopropazine hydrochloride

Partly block central cholinergic receptor and balance cholinergic and dopinergic activity in ganglia

Uses

In parkinsonism

Anaestheic, ganglionic blocking.antihistsamininc activity