Parasympatholytic drugs

Parasympatholytic drugs : 

Parasympatholytic drugs Submitted by P. Mahalingam BVM 06066

INTRODUCTION : 

A parasympatholytic element, also referred to as anticholinergics, reduces the activity of the parasympathetic nervous system The term parasympatholytic typically refers to the effect of a drug, although some poisons, such as organophosphates act to block the parasympathetic nervous system as well. INTRODUCTION 2

CLASSIFICATION : 

Anticholinergics are classified according to the receptors that are affected: Antimuscarinic agents operate on the muscarinic acetylcholine receptors. The majority of anticholinergic drugs are antimuscarinics. Antinicotinic agents operate on the nicotinic acetylcholine receptors. The majority of these are non-depolarising skeletal muscle relaxants for surgical use, along with a few of the depolarising agents and drugs of other categories structurally related to curare. CLASSIFICATION 3

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ANTIMUSCRINIC AGENTS THEY ARE CLASSIFIED INTO TWO SUB TYPES A-NATURAL Examples 1-Atropine. 2-Scopolamine. 3-Hyoscine. B-SYNTHATIC Examples 1-Homotropine. 2-Tropicamide. 3-Piorenzipine. 4-Isopropamide. 5-Benztropene 6-Benzhexone. 4

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GANGLIONIC BLOCKERS[ANTI NICOTINIC] Examples 1-Mecamylamine. 2-Nicotine. 3-Pempidine. 4-Hexamethonium. N-M BLOCKER[ANTI NICOTINIC] They can be further subdivided as follows A-DEPOLARIZERS Examples 1-Suxamethonium. 2-Decamethonium. 5

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B-COMPETITIVE Examples 1-Atracurium. 2-Doxacurium. 3-Metocurium. 4-Vecurium. 5-Tubocurarine. CHOLINEESTERASE REACTIVATOR Examples 1-Pralidoxamine. 2-Obidoxime. 6

Plant sources : 

The most common plants containing anticholinergic alkaloids are: Atropa belladonna (Deadly Nightshade) Brugmansia species (Brugmansia) Datura species (Datura) Hyoscamus niger (Henbane) Mandragora officinarum (Mandrake). Plant sources 7

PHARMACOLOGICAL EFFECTS : 

Effect on central nervous system: Scopolamine has greater effects on the CNS than atropine due to its ability to cross the blood-brain barrier. Atropine and scopolamine cause CNS depression characterized by amnesia, fatigue and reduction in rapid eye movement sleep. Hyoscine has anti-emetic activity, so is used for motion sickness. PHARMACOLOGICAL EFFECTS 8

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Effect on heart: Atropine acts on the M2 receptors of the heart and antagonizes the activity of acetylcholine. It causes tachycardia by blocking vagal effects on the sinoatrial node. If atropine is given by intramuscular or subcutaneous, it causes initial bradycardia 9

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Anticholinergic drugs are used in treating a variety of conditions: Gastrointestinal disorders (e.g., gastritis, pylorospasm, diverticulitis, ulcerative colitis) Genitourinary disorders (e.g., cystitis, urethritis, prostatitis) Respiratory disorders (e.g., asthma, chronic bronchitis) Parkinson’s disease and Parkinson-like adverse medication effects . 10

Possible effects of anticholinergics : 

Ataxia; loss of coordination Xerostomia or dry-mouth with possible acceleration of caries Increased body temperature Pupil dilation (mydriasis); consequent sensitivity to bright light (photophobia) Loss of accommodation (loss of focusing ability, blurred vision — cycloplegia) Double-vision (diplopia) Possible effects of anticholinergics 11

CLINICAL USES : 

ANTIMUSCARINICS: Atropine (D/L-Hyoscyamine) anaesthesia anticholinesterase poisoning bradycardia antispasmodic in gastrointestinal hypermotility Adverse effects: urinary retention xerostomia blurred vision CLINICAL USES 12

CLINICAL USES : 

Scopolamine (L-Hyoscine) motion sickness Ipratropium: in asthma and bronchitis Tropicamide, Cyclopentolate: produce mydriasis and cycloplegia in diagnostics Pirenzepine: in peptic ulcer CLINICAL USES 13

CLINICAL USES : 

USES OF ANTINICOTINIC DRUGS: Ganglionic blocking agents Rarely used for blood pressure decrease during surgery Nondepolarizing neuromuscular blocking agents muscle relaxant in anaesthesia. CLINICAL USES 14

REFERENCES : 

www.wikidoc.org/index.php/Nicotinic_antagonist www.angelfire.com/art2/sensony/cldrugs REFERENCES 15