Drugs used for the treatment of cough

Dr Aneela Khalid

LEARNING OBJECTIVES• Classification of drugs used for the non

specific treatment of cough• Define the term Expectorant and

mucolytic• Describe the mechanism of action,

adverse effects and clinical uses of • Expectorants• Antitussives

Classification of drugs used for non specific treatment of cough

1. Cough suppressants• Centrally acting Antitussives• Peripheral Antitussives2. Cough expectorants3. Antihistamines4. Bronchodilators

1) COUGH SUPPRESSANTS (Anti-tussives)

1- Centrally acting Antitussives Narcotic antitussive Opiates Codeine Pholcodine Hydrocodone Non narcotic antitussives Opiates Dextromethorphan Levopropozyphene Noscapine

Non-Opiates Diphenhydramine Benzonatate

2- Peripheral Antitussives1 Demulcents

LinctusLozengesLiquorice

2 InhalationWater aerosol inhalationBenzoinMenthol

3 Local anaestheticsBenzonatateLignocaine (only in special circumstances)

2) Cough Expectorants 1 Drugs acting Reflexly

IpecacuanhaAmmonium chloridePotassium Iodide

2 Drugs Acting DirectlyPotassium IodideGuaiphenesin

3 Mucolytics Acetylcysteine Bromhexine (Bisolvon) Carbocisteine Methylcysteine

Definition of Mucolytic and Expectorant

• Mucolytic• A mucolytic is a drug that breaks down thick

mucus, making it thinner and easier to cough out.

• Expectorant An expectorant is a drug which makes the cough

more productive by loosening and liquefying bronchial secretions.

Also known as Mucokinetics

AntitussivesAntitussives are substances that specifically inhibit or suppress the action of cough

1) Depression of medullary centre or associated higher centers.

2) Increases threshold of the cough centre.3) Interruption of tussal impulses peripherally in

the respiratory tract.4) Inhibition of conduction along the motor

pathways.

Narcotic AntitussivesCodeine and Pholcodeine An opium alkaloid similar to morphine less potent then morphine as analgesic and

respiratory depressant. 60% effective orally then parentrally as an

analgesic and respiratory depressant. A standard antitussive A small fraction of administered codeine is

metabolized to morphine which is responsible for analgesic effects of codeine.

MOA of Codeine:• Directly suppresses cough centre by binding to

distinct receptors in Medulla. • Suppresses cough for about 6 hrs. Dosage: 15 mg Adverse effects of Codeine:• In therapeutic doses minimum side effects

– Sedations, nausea, constipation• At higher doses respiratory depression and

drowsiness can occur.• Contraindicated in asthmatic patients and

patients with diminished respiratory reserves.

• Pholcodeine has similar efficacy as codeine with longer duration of action of 12hrs

• It has no analgesic or addiction property

Non Narcotic AntitussivesDextromethorphan Hydrobromide A synthetic compound. It is a dextrorotatory sterioisomer of a methylated

derivative of levorphenol. Strong and partial µ agonist. As effective antitussive as codeine. MOA:1. Controls cough spasm by depressing cough

centre in medulla2. Increase the threshold for coughing

Advantages of Dextromethorphan

– No effect on ciliary activity– No CNS depression– No addiction potential– No constipationDosage: 15- 30mg three or four times daily.

Toxicity:Toxic doses may cause.Stupor, ataxia, respiratory depression, convulsion in children and death with abuse of its purified powder.

• Contraindicated in children below 6 yrs of age and also in patients taking Monoamine oxidase inhibittors.

• Levopropoxyphene• It is a sterioisomer of weak opioid agonist

dextropropoxyphene. • It is devoid of opioid effects• Sedation is the only adverse effect• Dosage: 50-100mg 4hrly

Noscapine• An opium alkaloid• No narcotic, analgesic or dependance

inducing properties. • Equally effective antitussive as codeine• Useful for spasmodic cough.• Headache and nausea are usual side

effects• Contraindicated in asthamatic patients.

Benzonatate Chemically related to tetracaine. MOA:

Reduces the cough reflex by anesthetizing the stretch receptors in the respiratory passages, Lungs and Pleura.

It has some central effects also.Adverse effects:Headache, Dizziness, PruritusNasal Congestion, burning of eyes & tightness in chest.

EXPECTORANTSThese are the drugs which make the cough

more productive by loosening and liquefying bronchial secretions.

Also known as Mucokinetics.

Guaiphenesin It is a derivative of Guaiacol Obtained from wood or synthetically preparedMOA. Decrease sputum viscosity and increase

sputum volume thereby decreasing difficulty in expectoration

only FDA Approved expectorant . Adverse effects. Nausea, gastric disturbances

drowsiness and rash.

IPECACUANHA Source: Natural alkaloid obtained from

roots of cephaelis acuminata contains: – Cephaeline – Emetine

MOA. Loosening & liquefying mucosa soothing irritated bronchial mucosa. It also has emetic & amoebicidal properties.

• Uses. Mainly used for emesis in accidental poisoning.

• Contraindications Semiconscious, Unconscious or

convulsing person Corrosive poisoning or kerosine poisoning.

MucolyticsMOA of Mucolytics: Mucolytics open disulphide bonds in the

mucoproteins present in the sputum making it less viscid.

Bromhexine: MOA: It depolymerizes the

polysaccharides directly as well as by liberating lysosomal enzymes which breaks down the fiber network in the tenacious sputum.

Particularly useful for mucous plugs. Adverse effects: Rhinorrhoea, lacrimation, and gastric

irritation.

Antihistamines• Chlorphenaramine 2-5mg• Diphenhydramine 5-25mg• Promethazine 15-25mg• Anti histamines provides relief in cough due to

sedative and anticholinergic action.• They lack selectivity for cough centres • They have been promoted for treatment of

cough in allergic states.• No efficacy in Asthma

Bronchodilators• Bronchodilators by clearing secretions

through increase in surface velocity of airflow during cough relieves .

• Should be used only when element of bronchoconstriction is present and not routinely

• Fixed dose combination of bronchodilators with anti tussives not preferred .

Special conditions Cough may be useful or useless. No role of Antitussives Asthma young infants Congestive cardiac failure Bronchiactasis, COPD, Tuberculosis.

Antitussives may be prescribed For dry unproductive cough that is

hazardous or is disturbing sleep. ( hernias, piles, after surgical procedures

esp cataract surgery). Pholcodeine along with diphenhydramine

is useful. In whooping cough or in pertusis. Bronchodilator along with

Diphenhydramine is useful.