Expectorants, Antitussives, used for the treatment of cough and MCQ for NEET PG,GPAT, NIPER, Drug inspector and Pharmacist exam

COUGH: It is physiologically useful protective reflex that clears the respiratory tract of the accumulated mucus and foreign substances. It occurs due to stimulation of mechano/chemo receptors in throat, respiratory, passage or stretch receptors in the lung

Types of cough: It is of two types.

Non- productive: It is considered as serving no useful purpose, rather if increased discomfort to the patient. It is treated with antitussive agents.

Productive cough: It is characterized by presence of excessive sputum and may be associated with conditions such as chronic bronchitis. In this condition expectorants are useful.

CLASSIFICATION OF DRUGS:

A. Pharyngeal demulcents:

1. Lozenges

2.  Syrup

3.  Glycerine

4.  Liquorice

B. Expectorants

1.Bronchial secretion enhancers:

a. Potassium and sodium citrate

b. Potassium iodide

c. Guaiphenesin

d. Tolu balsam

e. Vasaka

f. Ammonium chloride

2. Mucolytics:

a. Bromohexine

b. Ambroxol

c. Acetylcysteine

d. Carbocysteine

C. Antitussives:

1. Opioid Antitussives:

a. Codeine

b. Pholcodeine

c. Ethylmorphine

2. Non-opioid antitussives:

a. Noscapine

b. Dextromethorphan

c. Chlophedianol

d. Prenoxydiazine

e. Pipazethate

3. Antihistaminics:

a. Chlorpehniramine

b, Diphenhydramine

c. Promethazine

D. Adjuvant antitussives:

1. Bronchodilators:

a. Salbutamol

b. Terbutaline

A. Pharyngeal demulcents: Pharyngeal demulcent sooth the throat and reduce afferent impulses from the inflamed, irritated pharyngeal mucosa, thus provide sympathomimetic relief in dry cough.

B. Expectorants: A medication that helps bring up mucus and other material from the lungs, bronchi and trachea. Increase bronchial secretions, reduce its viscosity, facilitating its removal by coughing, enhance the clearance of mucus.

1.Bronchial secretion enhancers(mucokinetics):

a. Potassium iodide: These are secreted by bronchial glands, can irritate the airway mucosa and increase bronchial secretions by salt action. It is sedative type of expectorant. It is also used as electrolyte relenisher.

Side effects:  If potassium iodide gives externally for prolong use can effect thyroid function and produce iodism.

b. Sodium and potassium citrate: These are considered to increase bronchial secretion by salt action.

c. Guaiphenesin, vasaka, tolu balsam: These are also used as expectorant which enhance bronchial secretion.

d. Ammonium Chloride (Ammonium muriate): Enhance respiratory secretions, sedative type of expectorant and cause side effects like nausea.

Note: U.S FDA has stopped marketing of all expectorants except guaiphenesin. Steam    inhalation and hydration are more useful.

2. Mucolytics: Alter the characteristics of mucus to decrease its viscosity and facilitate its removal of ciliary action.

a. Bromohexine: It is an alkaloid from vasaka plant. It depolymerises mucopolysaccahrides of mucus and also increase lysosomal enzyme activity that break the fiber network of tenacious sputum.

Side effects: G.I.T upset and menorrhoea (water release from nose).

b. Ambroxol: Metabolite of bromohexine and has similar mode of action.

c. Acetylcysteine: It is a mucolyte that decrease the viscosity of mucus by splitting the disulphide –s-s- bonds of mucoproteins.

d. Carbocysteine: It decrease viscid sputum in the same way as of acetylcysteine. In chronic bronchitis patient it may break the gastric mucus barrier. But contraindicated in peptic ulcer patients.

Side effects: Rashes and gastric discomfort.

e. Dornase-alpha: Highly purified solution of recombinant human (DNAse). These enzyme selectively cleaves DNA. Cystic fibriosis, pulmonary secretion contain very high amount of extracellular DNA.

Others: Drinking warm water, inhaling steam or menthol vapour surfactants such as tyloxapol, proteolytic enzymes such as chymotrypsin or trypsin are also used their hydrating or mucolytic action.

C. Antitussives: These drugs act in the CNS to raise the threshold of cough centre to reduce tussel impulses. Its main aim is to control rather than suppress cough. These are mainly useful for dry unproductive cough or if cough disturb sleep or is hazardous.

1. Opioid antitussives:

a. Codeine: An opium alkaloid less potent than morphine. More selective for cough centre and it is treated as standard antitussive. It suppresses cough centre for 6hr. Administered orally.

Side effect: Constipation, convulsions, postural hypertension and high dose cause respiratory depression.

b. Pholcodeine: It is structurally, related to codeine, but it is slightly more potent, longer acting and better tolerated then codeine. More suited for long time. It causes lesser constipation and drowsiness then codeine.

c. Ethylmorphine: It is very closely related to codeine which is also known as methylmorphine. It has antitussive, respiratory depressant properties and has less constipating effect.

2. Non Opioid antitussives:

a. Noscapine(Narcotine): An opium alkaloid of the benzoisoquinoline series. It depresses cough but has no narcotic, analgesic and dependence inducing properties. It act as antitussive like codeine and cough suppressant.

Side effects: At higher doses may produce nausea, headache and tremors. It can release histamine and produce bronchoconstriction in asthmatics.

b. Dextromethorphan: It is synthetic central NMDA ( N-methyl-D-aspartate) receptor antagonist or methyl ester of the dextroisomer of levorphanol. D-isomer is antitussive and l-isomer has analgesic action. It is as potent as codeine. It has less addiction liability, non-analgesic action, least constipating effect and minimal drowsiness. It is most popular cough suppressant.

Side effect: Nausea, drowsiness, dizziness and at higher dose cause hallucination, ataxia may occur.

c. Chlophedianol: Centrally acting antitussive with weak antihistaminic, anticholinergic and local anaesthetic properties. Onset of action is slow and longer acting.

Side effects: Dryness of mouth, irritability and vertigo.

d. Prenoxydiazine: It acts as antitussive by desensitizing the pulmonary stretch receptors. Tussel impulses in the lungs are suppressed. However it is not impressive.

e. Pipazethate: Phenothiazine group of antitussives, occassionaly used.

Note: Centrally and peripherally acting antitussives:

Benzonate: It is structurally related to local anaesthetic tetracaine. It is not only inhibit the afferent cough impulses to suppress the central cough centre, but also inhibit the pulmonary stretch receptors and also posses local anaesthetic action.

Side effect: Headache, nausea, drowsiness, higher dose cause vertigo.

3. Antihistaminics: Many H1 antihistaminics has been added to antitussives and expextorant formulations. They provide relief in cough but not able to suppress cough centre. They don’t have expectorant property. They have been use for cough in respiratory allergic states. Chlorpheniramine, Diphenhydramine and Promethazine are commonly used.

D. Bronchodilators: Salbutamol and Terbutaline are commonly used bronchodilators in cough. They stimulate pulmonary receptors which can trigger both cough and bronchoconstriction. These bronchodilators provide relief in cough and improve the effectiveness of cough in clearing secretions by increasing surface velocity of airflow during coughing. They should not be used routinely.

 MCQs:

1. Drugs that remove sputum from the respiratory tract are known as:

a. Emetics

b. Expectorants

c. Antidotes

d. None of them

2. Which of the following is sedative type of expectorant

a. Lemon oil

b. Ammonium chloride

c. Potassium iodide

d. Both b and c

3. What is the synonym of Ammonium chloride?

a. Ammonium muriate

b. Tartared antimony

c. Bakers ammonia

d. Preston salt

4. What is the synonym of Noscapine?

a. Terbutaline

b. Narcotine

c. Potassium iodide

d. Salbutamol

5. Ammonium chloride is used as?

a. As a diuretic

b. As an expectorant

c. As an acidifying agent

d. All of the above

6. Potassium iodide is used as?

a. As a source of iodine solution

b. As an expectorant

c. As an electrolyte replenisher

d. All of the above

7. Which drug depolymerises mucopolysaccharides of mucus?

a. Guaiphenesin

b. Nascopine

c. Bromohexine

d. Diphenhydramine

8. Which drug decrease the viscosity of mucus by splitting the disulphide –s-s- bonds of mucoproteins?

a. Bromohexine

b. Ammonium chloride

c. Potassium iodide

d. Acetylcysteine

9. Which bronchial secretion enhancer is approved by U.S FDA?

a. Guaiphenesin

b. Potassium iodide

c. Ammonium chloride

d. Potassium citrate

10. Which drug is synthetic central NMDA(N-methyl-D-aspartate) receptor antagonist?

a. Noscapine

b. Chlophedianol

c. Dextromethorphan

d. Prenoxydiazine

11. Which opioid suppresses cough centre for 6 hour?

a. Noscapine

b. Codeine

c. Ethylmorphine

d. Prenoxydiazine

12. Which drug act as centrally and peripherally acting antitussives:

a. Codeine

b. Ethylmorphine

c. Prenoxydiazine

d. Benzonate

13. Which drug cause nausea, drowsiness, dizziness and at higher dose cause hallucination, ataxia may occur

a. Noscapine

b. Chlophedianol

c. Dextromethorphan

d. Prenoxydiazine

14.“Dryness of mouth” is a side effect of which drug?

a. Noscapine

b. Chlophedianol

c. Dextromethorphan

d. Prenoxydiazine

15. Which antitussive desensitizing the pulmonary stretch receptors?

a. Prenoxydiazine

b. Dextromethorphan

c. Chlophedianol

d. Benzonate

ANSWERS:

1. b
2. d
3. a
4. b
5. d
6. d
7. c
8. d
9. a
10. c
11. b
12. d
13. c
14. b
15. a

Reference:

1. “K.D.Tripathi”Page no:237-240, 8th edition 2018.
2. “Snehal Chakorkar”, Expectorant and antitussive, Jan 9, 2020.
3. “Vijay Prasad Sangiseth”, Health and medicine, Nov 20,2013.

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