ANTITUSSIVE DRUGS

SUMREEN KOURMVSc ScholarVety Medicine

ANTITUSIVE DRUGS Agents used to relieve or

suppress coughing.

Benificial in suppressing cough & in decreasing morbidity in respiratory disease.

Indicated when cough is painful,unproductive,distressing,exhausting/exacebrate lung damage.

PATHOPHYSIOLOGY OF COUGH

Cough stimulus:pharynx Larynx

Tracheobronchial tree

Cough centre located in medulla oblongata

Impulse(afferent nerves): vagusGlossopharyngeal nerve

Effernet pathway supplies nerve : abdomen

thoracic muscles diaphragmic muscles

Forceful expulsion of air from lungs

TYPES OF COUGHCOUGH

Duration

Acute

Chronic

Subacute

Dry/Produtive

Dry Productive

CLASSIFICATION OF ANTITUSSIVE DRUGS

Peripherally acting/locally

acting :•Demulscents•Mucosal anaesthetics•Bronchodilators•Expectorants•Miscellaneous

Centrally acting

•Opioid/narcotics•Non-opioid/non –narcoptics.

DEMULCENTS: Includes: honey syrup glycerine liquorice They coat,protect & soothe throat

directly & promote salivation

reduce afferent

Impulse.

Provide symptomatic relief in dry cough.

MUCOSAL ANAESTHETICS BENZONATATE:

Long chain polyglycol derivative local anaesthetic.

Related to procaine & tetracaine. Reduce coughing –

bronchitis,emphysema,influenza,pneumonia.

Half life:3-8hrs.

MECHANISM OF ACTION Act as local

anaesthetic.

sensitivity to stretch receptors in lower airways & lungs

Reduces drive to cough.

SIDE EFFECTS Drowsiness. Numbness of mouth & throat. Dysphagia. Allergic reactions.

BRONCHODILATORS Drugs which causes an increase in calibre

of bronchus & bronchial tube. Used when there is: - bronchial narrowing - where improved alveolar ventillation is required. Improve effectiveness of cough in clearing

secretions. Ephedrine. Theophylline. Isoprenaline.

EPHEDRINE(ADRENERGIC AGONIST) Mixed acting non-catecholamine which

stimulates alpha & beta receptors.

Develop mild bronchodilation.

Produces decongestion in bronchi which helps to reduce mucosal swelling.

ISOPRENALINE No selective beta1 & beta2

adrenoceptor agonist. Can be used parentrally. Marked brochodilation: 1-2hrs.

EXPECTORANTS Expectorants are agents which increase

volume or fluidity of secretion in respiratory tract & fascilitate their removal by ciliary action.

Bromohexine Water aerosols

BROMOHEXINE Synthetic derivative of alkaloid vasicine

(adhatoda vasica). Useful if mucus plug present. Administered both oral & parentral

routes. Used: Bronchitis Bronchopneumonia Chronic cough

ACTION

Mucus clearance. Fascilitate expectoration Allow animal to breathe freely.

Depolymerises mucopolysacchrides directly & liberate lysosomal enzyme causing breakdown of network of fibres of tenacious sputum

Increases Ig level in airways secretions enhancing membrane permeability.

Active metabolite –stimulates & releases surfactant by type 2 pneumocytes –act as anti glue factor

WATER AEROSOL Used ocassionally to liquefy

hyperviscous mucus in repiratory tract. Aerosol/mist therapy only delivers few

mm of water to smaller pulmonary airways & lungs.

MISCELLANEOUS AGENTS Dropizine Levodropropizine

CENTRALLY ACTING Opioid antitussive: Codeine Hydrocodone Butorphanol Hydromorphone. Non opioid antitussive: Dextromethorphan Noscapine phoicodine

OPIOID/NARCOTIC DRUGS Potent inhibitors of medullary cough

centre at sub-analgesic dose -antitussive.

Assoiated with: Sedation Constipation Depression of respiratory centre

CODEINE Opiate alkaloid Available both as base & phosphate & sulphate salts. ACTION: Causes direct suppression cough centre

in medulla. Action can be blocked by naloxane. Onset of action after oral-30min.

PHARMACOKINETICS Conversion of codiene to morphine occurs

inn liver & is catalysed by cytochrome P450enzyme CYP2D6.

Binds to M opioid receptors & exert effect. SIDE EFFECT: Anorexia Vomition Constipation Biliary & pancreatic duct spasm. Depression.

CONTRAINDICATIONS Use with CNS depressants may increase

CNS /respiratory depressant action. Anticholinergic drug used with codiene

may increase chances of constipation. DOSE: Dogs:0,5-2 mg/kg PO

BUTORPHANOL Is synthetic opioid partial agonist Is potent analgesic and antitussive

agent After oral administration it is completely

absorbed but undergoes a significant first pass metabolism after oral administration

DOSE – DOG – 0.1-0.25 mg/kg bwt.

NON OPIOID ANTITUSSIVE Have been developed to increase safety of

centrally acting antitussive drugs. DEXTROMETHORPHAN: It’s a d-isomer of codiene aanalogue

levorphanol. Occurs as odourless to whit yellow

crystalline powder.

Mechanism of action: It acts as uncompetitive NMDA receptor

agonist & serotonin & norepinephrine transporter blocker at different concentrations.

Pharmacokinetics: Absorbed by gastrointestinal tract

enters blood stream & cross BBB. In liver it is metabolised by Cyt P450

enzyme metabolite dextrorphan

CONTRAINDICATIONS not used in allergic reactions

DRUG INTERACTIONS

Should not be administered along with MAOI or serotonin uptake inhibitor due to potential for serotonin syndrome – life threatening

DOSE – 1-2 mg/kg bwt

THANK YOU