Parasympatholytics (Anticholinergic Agents) temperature regulating centre in hypothalamus and also inhibits sweating Effect on gastrointestinal system: Atropine decreases the tone and motility of all parts of gastrointestinal tract It also decreases the amplitude of contraction and frequency of peristaltic wave of stomach and intestines Atropine also exerts a weak antispasmodic action on biliary tract and gall bladder Effect on other smooth muscles: Atropine relaxes the smooth muscles of bronchi and bronchioles which results in widening of the airways It is effective in relieving bronchospasm produced by cholinergic agents Atropine also produces reduction in normal and drug induced ureteral peristalsis It also tends to reduce the tone of the fundus of urinary bladder and enhances the tone of trigonal sphincter and may cause of retention of urine Effect on secretions: Atropine reduces the various body secretions e.g sweat, salivary, bronchial and lacrimal etc It also reduces the volume and total acidity of gastric secretion and, reduce the secretion of mucin and enzymes in the gastric secretions induced by cholinergic drugs It has no significant effect on intestinal and pancreatic secretions Effect on eye: Atropine produces mydriasis by blocking the cholinergic nerves supplying the smooth muscles of sphincter of the iris on local administration into the eye It also produces paralysis of accommodation or cycloplegia (the condition in which, one can see things 163 clearly only at a long distance and can not constrict the pupil for viewing the near objects clearly) Atropine induced mydriasis can be distinguished from the mydriasis produced by sympathomimetic amines as the latter not produce cycloplegia Pharmacokinetics All the belladonna alkaloids are well absorbed from the GIT, from the site of injection and the mucous membrane They are distributed throughout the body and cross the blood-brain barrier About 50% of the atropine is metabolized in liver and remaining portion is excreted unchanged in urine Atropine cross the placental barrier and is secreted in milk and saliva Adverse Reactions The adverse reactions are due to the peripheral muscarinic blockade and central actions The general side effects include dry mouth, difficulty is swallowing, thirst, dry skin, skin rash, flushed skin etc It also produces constipation, urinary retention, impotence, difficulty in micturition, tachycardia, palpitation, postural hypotension, dilatation of pupil, photophobia, blurred vision, dizziness, fatigue, anxiety and tremors etc Toxic doses can gives rise to acute belladonna poisoning which is characterized by depression of vasomotor centre, vasomotor collapse, coma and depression of respiratory centre Acute belladonna poisoning can be treated by administering universal antidote before gastric lavage, physostigmine in the dose of 1-4 mg SC can be administered after a interval 164 of one to two hours until a satisfactory response is obtained For urinary retention catheterization can be done and patients is kept in dark room to alleviate photophobia Therapeutic Uses Gastrointestinal colic (as antispasmodic): Belladonna alkaloids relax the spasm of smooth muscles of intestinal, urinary and biliary tract They are also effective in functional and drug induced diarrhoea, to relieve urinary urgency and frequency and enuresis in children They are also used to reduce gastric secretion in peptic ulcer patients Also, used to reduce the excessive sweating in tuberculosis and sweating and salivation in parkinsonian patients CNS disorders: Scopolamine and hyoscine are effectively used in the treatment of nausea, vomiting and motion sickness Centrally acting anticholinergic/ antihistaminics e.g trihexyphenidyl are used in parkinsonism Pre-anaesthetic medication: These agents reduce the salivary and respiratory secretion and are administered half an hour before general anaesthesia They also prevent laryngospasm Atropine is given in combination with morphine as a preanaesthetic medication to antagonize the central depressant action of morphine on respiration In organophosphorus poisoning: Atropine is used in mushroom poisoning due to muscarine On CVS: Atropine is used for counteracting bradycardia and partial Section 3/ Drugs Acting on ANS heart block in some patients of myocardial infarction A s m y d r i a t i c a n d c y c l o p l e g i c agent: Atropine is used to produce mydriasis and cycloplegia for testing errors of refraction Mydriasis is required for fundoscopic examination and in the treatment of iritis and keratitis ANTIMUSCARINICS (SEMISYNTHETIC SYNTHETIC) AND HOMATROPINE More potent than atropine Used in eye and onset of mydriasis and cycloplegia is similar to that of atropine but homatropine is not much used for producing cycloplegia CYCLOPENTOLATE It is more potent and rapidly acting as compared to homatropine for producing mydriasis and cycloplegia especially in children It is also used in iritis TROPICAMIDE It is used for refraction testing in adults and as mydriating agent for fundoscopy It has quickest and briefest action ATROPINE METHONITRATE It is used for abdominal colic and in aerosol form it is used in bronchial asthma IPRATROPIUM BROMIDE It is a valuable drug used in the treatment of chronic obstructive pulmonary disease Parasympatholytics (Anticholinergic Agents) (COPD) by inhalation route Titropium bromide is congener of ipratropium bromide producing long lasting bronchodilatation DICYCLOMINE It has got antispasmodic with direct smooth muscle relaxant action It is used in morning and motion sickness GLYCOPYRROLATE Rapidly acting antimuscarinic lacking central effects Used for preanaesthetic medication ISOPROPAMIDE Indicated in hyperacidity, dyspepsia, irritable bowel syndrome Propantheline, oxyphenonium, panthienate are useful in peptic ulcer and gastrointestinal hypermotility Pipenzolate and mephenzolate are useful in dyspepsia and infantile colics 165 MEBEVERINE It shows effect on colonic muscle activity It is indicated in smooth muscle spasm PIRENZEPINE Selective M muscarinic receptor blocker It inhibits gastric secretion Thus is effective in peptic ulcer patients and promotes ulcer healing It does not produce atropinic side effect (due to blockade of M2 and M3 receptors) Only 20-30% oral bioavailability and is excreted unchanged in urine FLAVOXATE It produces direct relaxant action on smooth muscle with analgesic and anaesthetic action and used in the treatment of dysuria, nocturia and urinary urgency and frequency associated with cystitis and urethritis This page intentionally left blank Section Drugs Acting on Cardiovascular & Urinary System ... is used for refraction testing in adults and as mydriating agent for fundoscopy It has quickest and briefest action ATROPINE METHONITRATE It is used for abdominal colic and in aerosol form it... of atropine but homatropine is not much used for producing cycloplegia CYCLOPENTOLATE It is more potent and rapidly acting as compared to homatropine for producing mydriasis and cycloplegia especially... e g i c agent: Atropine is used to produce mydriasis and cycloplegia for testing errors of refraction Mydriasis is required for fundoscopic examination and in the treatment of iritis and keratitis