Download - Antitussive drugs
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.
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
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.
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.
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