Dr. RAGHU PRASADA M SMBBS,MDASSISTANT PROFESSORDEPT. OF PHARMACOLOGYSSIMS & RC.

Cough is a useful physiological mechanism thatserves to clear the respiratory passages of foreignmaterial and excess secretions.

Cough reflex is complex, involving the central andperipheral nervous systems as well as the smoothmuscle of the bronchial tree.

It should not be suppressed discriminately. Chronic cough can contribute to fatigue, especially in

elderly patients, in such situations the physiciansshould use a drug that will reduce the frequency orintensity of the coughing.

It has been suggested that irritation of the bronchialmucosa causes bronchoconstriction, which in turn,stimulates cough receptors (which probablyrepresent a specialized type of stretch receptor)located in the tracheobronchial passages.

Stimulation of mechano-or chemoreceptors (throat,respiratory passages or stretch receptors in lungs)

Afferent impulses to cough centre (medulla)

Efferent impulses via parasympathetic & motornerves to diaphragm, intercostal muscles & lung

Increased contraction of diaphragmatic, abdominal& intercostal (ribs) musclesnoisy expiration

(cough)

PRODUCTIVE COUGHNON-PRODUCTIVE COUGH

Expectorants- increase the volume and decrease theviscosity of secretions to enhance the propulsion ofthese secretions upward and outward by ciliarymovement and coughing

Opioids –codeine, pholcodeineNon-opioids-Dextromethorphan, noscapine andpipazethateCodeine –Semisynthetic opioid analgesic

-potent cough suppressant action-10mg BD/TDS-lesser

addiction/constipationOverdose-Resp. depression, convulsion, posturalhypotension, tachycardia

Structurally related to codeineMore potent, longer acting and better toleratedthan codeineCauses lesser constipation and drowsiness thancodeineGiven orally 10-15mg BD

It is methyl ester of dextroisomer of levorphanolMOA-NMDA receptor antagonistIt has least addiction, no analgesic action(unlike levorphanol) least constipating effects and minimaldrowsinessAs potent as codeine -10mg TDSUses: Cough suppressant, used for temporary relief ofcough caused by minor throat & bronchial irritation(accompanies with flu & cold), pain reliefAdverse Effects Nausea, vomiting, drowsiness, dizziness, blurred vision

Naturally occurring opium alkaloid belonging tobenzylisoquinoline groupDevoid of analgesic activity, drowsiness and liabilityHas minimal constipating effects and popular coughsuppressantGiven orally-15mg TDS-produce headache and tremors

Phenothiazine group of antitussive occasionally usedin cough mixtures

Negligible CNS depressants –orally 40mg-TDS

Morphine-powerful cough suppressant, but long termuseconstipation

BENZONATATEIt is an antitussive structurally related to the localanaesthetic tetracaineInhibits the afferent cough impulses to suppress thecentral cough centre, but also inhibits the pulmonarystretch receptors has central as well as peripheralmechanism of actionIt possesses mild local anaesthetic actionOrally 100-200mg TDSS/E- drowsiness, Nausea, Headache

Indirect peripherally acting cough suppressant Provide protective coating over sensory receptors on

pharynx Honey, liquorice, syp tolu, syp VasakaPRENOXDIAZINE-acts by inhibiting pulmonary stretch receptors to

relieve bronchospasmIt has moderate antitussive actionOrally 100-200mg TDS

Local anaesthetic-Xylocaine, Bupivaciane- applied on pharynx and larynxand decrease sensitivity of receptorsAntitussive –not to be used in cough associated withbronchial asthma or chronic bronchitis orbronchiectasis harmful retention and thickening ofsputum

Drugs either increase or decrease the viscosity ofrespiratory secretions and facilitate their removal byciliary action and coughing by mucolytic and mucokineticactionMucolytic expectorantsThey alter the chemical charecteristics of mucous todecrease its viscosity and to facilitate its removal by ciliaryaction or coughing. Commonly used mucolytics- acetylcysteine, carbocysteine, Bromexine, Ambroxol andDornase-alfa

BROMHEXINE-Synthetic derivative of vasicine (alkaloid=Adhatoda vasica)MOA of Bromhexinea) Thinning & fragmentation of mucopolysaccaride fibersb) ↑ volume & ↓ viscosity of sputum

ACETLYL CYSTEINEMucolytic, that decreases viscosity of mucous bysplitting the disulfide (-S-S-) bonds of mucoproteins↓viscosityThis action facilitated by Alkaline pH-7-9

Acetyl cysteine (cont..)Nebulizn- 3-5ml of 20% solnOnset of action quick---used 2-8 hourlyUsesCystic fibrosis (to viscosity of sputum)Chronic bronchitisTreatment of paracetamol poisoningUnlabelled use includes the treatment of dry eyes(keratoconjunctivitis sicca as 5% acetyl cysteine with

hyperomellose

Adverse effectsNausea, vomiting, bronchospasm in bronchial asthma

CARBOCYSTEINE-has protected –SH group thereforecannot work through SH group and –S-S- interchangeIt cannot split the disulphide bonds of mucus

AMBROXOL-metabolite of bromexine- mechanism similar to bromexine- more useful in mucus plugs- 30mg TDS

These expectorants stimulate the flow of respiratorytract secretions by stimulating the bronchialsecretory cells (to increase the volume) and ciliarymovements (to facilitate their removal

Can also stimulate GI mucosa increase resp. sectrn Ammonium chloride, Sodium citrate Guaiacol,

Guiaifenesin

Essential oils- oil anize, oil eucalyptus Provide mild exp. By directly stimulating the

bronchial secretory cellsAmmonium chloride –cough expectorant in variouscough mixtures-gastric irritant reflex bronchial sectrnSodium citrate-conventionally used in several coughmixtures.After absorption, citrates get converted to

bicarbonates invivo and mucous becomes less viscous

Obtained from creosate woodSafe expectorants with proven efficacyGUAIFENESIN -Less irritating derivative of guaiacolAfter absorption-secreted into bronchial glands-increase airway secretion and mucosal ciliary activityOral-100-200mg TDS