Anticholinergic System And Drugs Question And Answers

Anticholinergic System And Drugs

 

Question 1. What Are Parasympatholytics? Classify Them. Describe Pharmacological Action, Therapeutic Uses, And Side Effects Of Atropine.
Answer:

Parasympatholytics are also known as anticholinergic drugs.

These drugs block the action of acetylcholine mediated through muscarinic receptors.

Classification Of Parasympatholytics

1. Natural alkaloids: Atropine, hyoscine

2. Semisynthetic derivatives: Hyoscine butyl bromide, homatropine, atropine mononitrate, ipratropium bromide, Tiotropium bromide.

3. Synthetic compounds:

• Mydriatics: Cyclopentolate, tropicamide
• Antisecretory-Antispasmodics:

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• • Quaternary Compounds: propantheline, oxyphenonium, aclidinium, isopropamide, glycopyrrolate.
  • Tertiary amines: dicyclomine, valethamate, pirenzepine.

4. Vasicoselective: Oxybutynin, Flavoxate, Tolterodine.
5. Antiparkinsonism: Trihexiphenydyl, procyclidine, biperiden.

Atropine

Pharmacological Actions

• CNS: Atropine at its therapeutic dosages produces a mild CNS stimulant effect. It reduces cholinergic overactivity in basal ganglia and produces anti-parkinsonian activity.
  It also suppresses vestibular disturbance and produces anti-motion sickness effect. At its high doses, it leads to restlessness, excitement, agitation, hallucination, medullary paralysis, coma, and death.
• CVS: Atropine at its low dosages causes blockage of presynaptic muscarinic autoreceptors on vagal nerve endings and produces mild bradycardia.
  At its therapeutic doses, it blocks M2 receptors of the heart and produces tachycardia. It improves AV conduction too. At its high doses, it leads to flushing of the face and hypotension.
• Glands: All secretions, i.e. sweat, salivary, lacrimal, tracheobronchial, nasal, etc. under cholinergic influence decrease due to blockage of M3 receptors. It produces dryness of skin and mucous membranes.
• Eye: Atropine blocks M3 receptors and causes paralysis of constrictor pupillae muscles which leads to passive mydriasis.
  Atropine due to blockage of M3 receptors also causes paralysis of ciliary muscles which causes loss of accommodation which leads to cycloplegia.
• GIT: Atropine reduces the tone as well as motility of the gut and increases the tone of the sphincter which can cause constipation. Atropine causes relaxation of the smooth muscle of the gallbladder.
• Bronchi: It causes relaxation of bronchial smooth muscle. It decreases bronchial secretion and also leads to mucociliary clearance which causes formation of mucous plug which blocks the airway.
• Urinary bladder: Atropine causes relaxation of the detrusor muscle of the bladder and increases the tone of the sphincter which leads to urinary retention.

Therapeutic Uses

• In ophthalmic system
  • It is used as mydriatic and cycloplegic for testing the refraction.
  • It is used as a mydriatic for fundoscopic examination.
  • It is used in iridocyclitis to break and prevent adhesion between the iris and lens.
• Preanesthetic medication: Atropine is used before giving general anesthesia to:
  • Prevent vagal bradycardia at the time of anesthesia.
  • Prevent laryngospasm by decreasing respiratory secretions.
• In poisoning
  • It acts as a life-saving drug in organophosphorus poisoning.
  • In some of the mushroom poisonings, it is the first drug of choice to be used.
• As antispasmodic: Atropine is used as antispasmodic drug indysmenorrhea, intestinal colic and renal colic.
• As vagolytic: It is useful for treating sinus bradycardia and partial heart block which occur due to an increase in vagal activity. Due toitsvagolyticeffctitimprovesAVconduction.
• In peptic ulcer: It decreases gastric secretion in fasting as well as in the neurogenic phase and provides symptomatic relief in peptic ulcer.
• In pulmonary embolism: Atropine provides benefits by reducing the reflex secretions.
• In bronchial asthma and COPD: Atropine leads to the drying of the secretion in the respiratory tract and leads to the plugging of bronchioles.

Adverse Effects

• GIT: Xerostomia, dryness of throat, dysphagia, constipation, etc.
• Eye: Headache, photophobia, blurring of vision, in elderly patients it can precipitate acute congestive glaucoma.
• Urinary tract: Presence of urinary retention, difficulty in micturition.
• CNS: At high doses, it leads to delirium, excitement, and hallucination.
• CVS: Atropine causes hypotension, tachycardia and palpitation.
• Acute belladonna poisoning: In severe poisoning, it can lead to coma and convulsion.

Question 2. Discuss Pharmacological Basis Of Use Of Atropine In Iridocyclitis.
Answer:

Iridocyclitis is inflammation of the iris and ciliary muscle. When there is inflammation in the iris it causes hyperemic dilatation of blood vessels and exudation of fluids due to which there is swelling in the iris causing sickness and contraction of the pupil.
So now the iris contact with the lens and adheres to it, to prevent this atropine as drop is used. Atropine is used in iridocyclitis because of the following advantages.

• It relaxes the iris and ciliary body by inducing cycloplegia and mydriasis.
• It reduces hyperemia.

Question 3. Write Briefl On Therapeutic Uses Of Atropine.
Or
Write A short note on therapeutic uses of atropine.
Answer:

The following are the therapeutic uses of atropine:

• In ophthalmic system
  • It is used as mydriatic and cycloplegic for testing the refraction.
  • It is used as a mydriatic for fundoscopic examination.
  • It is used in iridocyclitis to break and prevent adhesion between the iris and lens.
• Preanesthetic medication: Atropine is used before giving general anesthesia to:
  • Prevent vagal bradycardia at the time of anesthesia.
  • Prevent laryngospasm by decreasing respiratory secretions.
• In poisoning
  • It acts as a life-saving drug in organophosphorus poisoning.
  • In some of the mushroom poisonings, it is the first drug of choice to be used.
• As anti­spasmodic: Atropine is used as an anti-spasmodic drug in dysmenorrhea, intestinal colic, and renal colic.
• As vagolytic: It is useful for treating sinus bradycardia and partial heart block which occur due to an increase in vagal activity. Due to its vagolytic effect, it improves AV conduction.
• In peptic ulcer: It decreases gastric secretion in fasting as well as in the neurogenic phase and provides symptomatic relief in peptic ulcer.
• In pulmonary embolism: Atropine provides benefits by reducing the reflux secretions.
• In bronchial asthma and COPD: Atropine leads to the drying off of the secretion in the respiratory tract and leads to the plugging of bronchioles.

Question 4. Write Short Note On Atropine Substitutes.
Answer:

Atropine substitutes are semisynthetic derivatives of belladonna alkaloids and a large number of synthetic compounds which are introduced with the aim of producing more selective action on certain functions.

Atropine substitutes are used for selective or very rarely selective action over a particular organ and to avoid side effects.

Atropine Substitutes Are:

1. Quaternary compounds: Hyoscine butyl bromide, atropine methonitrate, ipratropium bromide, tiotropium bromide, propantheline, oxyphenonium, clidinium, pipenzolate methyl bromide, isopropamide, glycopyrrolate.
2. Tertiary amines: Dicyclomine, valet hamate, pirenzepine
3. Vasicoselective drugs: Oxybutynin, tolterodine, flvoxate
4. Mydriatics: Homatropine, cyclopentolate, tropicamide
5. Anti-parkinsonian: Trihexyphenidyl, procyclidine, and Biperiden

• Homatropine: It is a semisynthetic atropine derivative. The potency of homatropine is less than atropine. It acts in 1 to 3 days.
• Ipratropium bromide and Tiotropium bromide: These are synthetic atropine derivatives that are given by inhalation route. They have selective action over bronchial smooth muscle and cause bronchodilatation. Tiotropium has longer action than ipratropium. Xerostomia is the main side effect.
• Cyclopentolate, and tropicamide: These are synthetic atropine derivatives having a rapid onset of action along with a shorter duration of action as compared to atropine. Cyclopentolate acts for 24 hours while tropicamide is short-acting, i.e. for 6 hours.
• Propantheline: It is indicated in peptic ulcers and as antispasmodic. In the modern era, it is rarely used.
• Clidinium: It is a quaternary compound and has antisecretory and anti-spasmodic properties. It is used in peptic ulcer and irritable bowel syndrome.
• Glycopyrrolate: It is a quaternary compound with very rare central side effects. It is used in pre-anesthetic medication.
• Dicyclomine: It is a tertiary amine. It has anti-spasmodic and antiemetic properties. It is used in dysmenorrhea and abdominal colic.
• Valethamate: It is a tertiary amine. It has anti-spasmodic properties. It is used in intestinal and urinary colic.
• Oxybutynin: It has selective action on M1 and M3 receptors in the urinary bladder and salivary gland. This drug has vasico selective action. So it is used in relieving spasms after urologic surgery and for increasing bladder capacity in paraplegic and in nocturnal enuresis.
• Flavoxate: It has selective action on M1 and M3 receptors in the urinary bladder and salivary gland. It is used in relieving urgency and frequency because of cystitis, prostatitis, and urethritis.
• Tolterodine: Its action is more selective for the urinary bladder as compared to salivary glands. It is used to decrease frequency and urgency in detrusor overactivity.

Question 5. Write Down The Drug Treatment Of Organophosphorus Poisoning.
Answer:

Following is the drug treatment for organophosphorus poisoning.

• Atropine is given 2 mg IV repeatedly every 10 min. till dryness of the mouth or other signs of atropinization may be required for 1-2 weeks.
• Pralidoxime injected IV in doses of 1 to 2 gm.
• Diazepam should be given to control convulsions
• IV saline should be given.

Question 6. Explain why atropine is the live­saving drug in patients with organophosphorus poisoning.
Answer:

Atropine is highly effective in countering the muscarinic symptoms produced by organophosphorus compounds.

At high doses, it antagonizes the central effects. So it acts as a life-saving drug in patients with organophosphorus poisoning.

Atropine reverses all muscarinic symptoms such as coma, bronchoconstriction, increase in secretions, diarrhea, etc.

Question 7. Write On Drugs For Treatment Of Organophosphorus Poisoning.
Answer:

The following are the drugs for the treatment of organophosphorus poisoning:

• Atropine: Atropine is highly effective in countering the muscarinic symptoms produced by organophosphorus compounds. At high doses, it antagonizes the central effects.
  So it acts as a life-saving drug in patients with organophosphorus poisoning. Atropine reverses all muscarinic symptoms such as coma, bronchoconstriction, increase in secretions, diarrhea, etc.
  Atropine is given 2 mg IV repeatedly every 10 min till dryness of the mouth or other signs of atropinization appears. Continue treatment with maintenance doses may be required for 1-2 weeks.
• Pralidoxime: Since atropine is not effective for the reversal of neuromuscular paralysis, neuromuscular transmission is improved by giving cholinesterase reactivators such as pralidoxime. Organophosphorus compounds inactivate cholinesterases by phosphorylating
  ecstatic site of the enzyme.
  Oximes bind with high affinity to the anionic site, dephosphorylate the enzyme, and reactivate it.
  Early administration of oximes is necessary before the phosphorylated enzyme undergoes aging and becomes resistant to reactivation.
• Diazepam: Diazepam should be given to control convulsions.