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ANTITUSSIVE BY SHAIKH JAVEED M. Pharm (Pharmacology) 1

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Contents Introduction Definition Mechanism of cough production Types of cough Classification Antitussives MOA Drugs Screening methods 2

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Introduction Symptom of respiratory system: no sputum---antitussives Cough sputum --- expectorants Asthma ----- antiasthmatic drugs 3

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DEFINITION ANTITUSSIVE:- A drug that suppresses coughing possibly by reducing the activity of the cough center in the brain. EXPECTORANT:- A drug that enhances the secretion of sputum. 4

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Cough receptors (chemo-and-mechano receptors ) lie in mucosa of the bronchial tree from the nose to the distal bronchi. The impulses from these receptors are transmitted through the vagus and glossopharyngeal nerves to the cough center in the medulla. 5

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Mechanism of cough production The cough receptors lie in the mucosa of the bronchial tree. Afferent impulses passes to the medulla. Then an autonomic sequence of events is triggered by medulla causing certain effects. 7

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Two Basic Types of Cough Productive cough Congested, removes excessive secretions Nonproductive cough Dry cough 8

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Classification of cough Acute:- less than 3 weeks. Sub-Acute:- between 3-8 weeks. Chronic:- longer than 8 weeks. 9

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COUGH PHYSIOLOGY Cough Reflex:- -Initiated by irritation of sensory receptors in the respiratory tract. -To remove secretion of foreign objects. 10

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Coughing Most of the time, coughing is beneficial Removes excessive secretions Removes potentially harmful foreign substances 11

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CLASSIFICATION CENTRALLY ACTING ANTITUSSIVE:- Narcotic antitussive:- Codeine Hydrocodone Oxycodone Non-narcotic antitussive:- Dextromethorphan Noscapine Propoxyphene 12

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CLASSIFICATION 2) PERIPHERALLY ACTING ANTITUSSIVE:- Mucosal anaesthetics:- Benzonatate Chlophedianol Hydrating agents:- Steam Aerosols Miscellaneous:- Bromhexine 13

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ANTITUSSIVE MOA OPIOIDS:- Suppress the cough reflex by acting on the cough center in the medulla. NON-OPIODS:- Suppress the cough reflex by numbing the stretch receptors in the respiratory tract and preventing the cough reflex from being stimulated 14

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ANTITUSSIVE INDICATION Used to stop the cough reflex when the cough is non-productive i.e dry cough. 15

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ANTITUSSIVE CONTRAINDICATIONS Asthma COPD Hypersensitivity Head injury Pregnancy 16

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Codeine Selectively suppress cough center in medulla oblongata. Pharmacokinetics: Well absorbed from oral and injection. 10% converted to morphine through demethylation. Clinical Uses: Dry cough 17

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Codeine: Brand Names Codifos Corex Codokuff Cufex Tossex 18

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Codeine: Possible Side Effects Shortness of breath Sedation Euphoria allergic reactions constipation 19

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Hydrocodone Antitussive agent Analgesic agent more potent than codeine 5mg of hydrocodone is equivalent to 30 mg of codeine when administered orally Is combined with an anticholinergic drug (homatropine) 20

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Hydrocodone: Possible Side Effects Light-headedness Sedation Constipation allergic reactions 21

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Dextromethorphan Dextrorotatory stereoisomers of a methylated derivative of levorphanol. Clinical Use: Dry cough. 22

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Dextromethorphan: Brand Names Suppressa Corex-DX Cotuss 23

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Dextromethorphan :Possible Side Effects Slow breathing Confusion, hallucinations Anxiety Restless feeling Nervousness 24

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Benzonatate Is a non-narcotic cough medicine It works by numbing the throat and lungs, making the cough reflex less active 25

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Benzonatate: Possible Side Effects Headache Drowsiness Upset stomach Constipation Mild itching or skin rash 26

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ANIMAL MODELS 27

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ANIMAL MODELS Antitussive activity after irritant inhalation in guinea pig. Cough induced by mechanical stimulation. Cough induced by stimulation of the nervus laryngicus superior. Cough induced by ammonia in the cat Cough induced by sulfuric acid in the dog 28

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Antitussive activity after irritant inhalation in guinea pig Purpose and rationale:- The sensitive receptars are located in bronchial tree and stimulated mechanically and chemically. Requirements : Guinea pigs (300-400g), 7.5% Citric acid in water, Test & standard substance, Cylindrical glass vessel. Cylindrical glass vessel with 2 tubes at either ends. 29

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Procedure:- Guinea pig of either sex 300-400gm Animal placed in cylindrical glass vessel Guinea pig exposed to aerosol of 7.5% citric acid in water 10 min No of tussive response is registered One hour later test substance is applied s.c or orally After 30 min guinea pig is subjected to aerosol again 30

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Evaluation:- The number of coughs after treatment is expressed as percentage of the control period. Using various doses ED50 values can be calculated. 31

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Cough induce by mechanical stimulation Purpose and rationale : Cough can be induced by mechanical stimulation of the trachea in anesthetized guinea pigs. Requirements : Male guinea pigs (350-400g), Test drug, Standard drug-codeine(15, 30, & 60mg/kg), Thin steel wire. Thin steel wire inserted into trachea 32

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Procedure : Male guinea pigs are lightly anesthetized. Maintain constant body temperature of 370C by means of heated plate. Thin steel wire is gently inserted into the trachea through a small incision near cricoid cartilage. Coughs are evoked by pushing the steel wire to reach bifurcation of trachea Animals are randomly assigned to receive the test drug at various doses or the standard (codeine 15, 30, 60mg/kg).Ten animals per dose are used. 33

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Evaluation : Evaluation of statistical significance of the result is performed with student’s t-test. ED50 values determined by logit transformation. 34

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Cough induced by stimulation of the nervus laryngicus superior : Purpose and rationale : Stimulation of Nervous laryngicus superior induces coughing. Antitussive agents with predominately central action suppress the coughing reflex. Requirements : Cats of either sex(2-3kg), Pentobarbital (40mg/kg), Test compound, Standard – Codeine phosphate Fleisch tube pneumotachograph. Fleisch tube pneumotachograph 35

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Procedure : Cats of either sex are anesthetized. The fur is shaved ventrally at the neck & small incisions are made at both sides of larynx. The trachea is cannulated. The cannula is connected with Fleisch tube One femoral artery and one femoral vein is cannulated Small hook electrodes are attached to each laryngeal nerve and Wave impulses are applied every 5min (control) Intensity of forced expiration is measured by Fleisch pneumotachograph & recorded with blood pressure on a polygraph. The stimuli are repeated 36

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Evaluation : Total or partial suppression of forced expiration are recorded over time & expressed as percentage of control. 37

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Cough induced by ammonia in the cat Purpose and rationale : Cough is induce with the help of ammonia. Requirements : Cats, 6% pentobarbitone sodium, smoked paper kymograph, Tracheal cannula, ammonia vapour, polythene tube. 38

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Procedure : Cats are lightly anaesthetized. The trachea is then cannulated; The carotid artery is connected to a mercury nanometer. Injections are made intravenously in the femoral vein. Coughs are recorded on a smoked kymograph by a lightly sprung lever Ammonia is lead into respiratory system by means of a three way tap. 39

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The cat is allowed to inhale ammonia vapour for one inspiration. The cough stimuli are applied every three minutes until 3 or 4 control cough responses of similar intensity and duration are obtained. The test drug is then administered intravenously and cough stimuli are repeated at similar intervals until the cough response returns to normal. 40

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Evaluation : codeine is used as the antitussive standard, since it supresses coughing completely at a dose of 2mg/kg or less. Pholcodeine an dihydrocodeine are approximately as potent as codeine. The test drugs are scored accordingly. 41

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Cough induced by sulfuric acid in the dog Rationale: Cough is induce with the help of sulfuric acid Requirments: Dogs, De Vilbiss nebulizers,0.5M Sulfuric acid, Codeine, dihydrocodeine, test antitussive drugs. 42

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Procedure: Dogs are placed in a special wooden box. Through two holes a fine vapour of 0.5M sulfuric acid is sprayed. A count of the number of coughs is obtained by listening through earphones to a microphone attached to the dog`s throat. After two test periods 1 hour apart, a drug is given before the next test period. 43

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Evaluation: The percent inhibition is obtained by dividing the number of coughs by the number of coughs during the control period. 44

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Referensces Vogel, W.H., Scholkens, B.A., Sandow, J., Muller, G. and Vogel W.F.,: Drug Discovery and Evaluation Pharmacological Assays. 2nd ed. Spinger-Verlag Berlin Heidelberg, New York, Germany, pp. 352-376 (2002). Turner, R.A., Hebborn, P.,: Screening Methods of Pharmacology, Vol.-1. Academic Press, London, pp. 238 (1971). www.wikipedia.com. Tripathi, K.D.,: Essentials of Medical Pharmacology. 5th ed. Jaypee Brothers Medical Publishers (P)Ltd., New Delhi, India, pp. 195, 209 (2004). www.googleimages.com 45

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THANK YOU 46

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