Lecture 8 Expectorants and Emetics, Introduction

EXPECTORANTS & EMETICS

Introduction • Expectorants are the drugs that help in removing sputum from the respiratory tract either by increasing the fluidity (or reducing the viscosity) of sputum or increasing the volume of fluids that have to be expelled from the respiratory tract by coughing. • Examples of inorganic expectorants are ammonium chloride,

potassium iodide, sodium iodide and related substances. • If the patient is sensitive, dose of expectorant is high enough, this may induce vomiting (emetic action). Hence, it is advisable to give

the doses of expectorants that could be tolerated (by the patient) along with other pharmaceutical aids (flavours, sweeteners, etc.) and cough suppressants.

Classification of Expectorants • Classification of expectorants is according to their mechanism of action (i) sedative type and (ii) stimulant type. Sedative expectorants. These are stomach irritant expectorants

which are able to produce their effect through stimulation of gastric reflexes. • Examples of sedative expectorants include bitter drugs such as ipecac, senega, Indian squill, and compounds such as antimony potassium tartrate, ammonium chloride, sodium citrate, potassium iodide, etc.

Classification of Expectorants Stimulant expectorants. These are the expectorants which bring about a stimulation of the secretory cells of the respiratory tract

directly or indirectly. Since these drugs stimulate secretion, more fluid gets produced in respiratory tract and sputum is diluted. • Examples of stimulant expectorants include drugs such as Eucalyptus, lemon, anise, and active constituents of oil like terpine bydrate, anethole.

Emetics • These are the drugs which give rise to forced regurgitation (emesis) by which the contents of the stomach get expelled through the oral cavity. • Emetics constitute a valuable part of treatment in posioning cases. • The emetics act either by

- local irritation of gastric mucosa (ammonium bicarbonate, ipecacuanha) - directly on the chemoreceptor trigger zone in the floor of IV

ventricle in medulla (i.e., centrally acting emetics). • Emetics are sometime added to cough preparations in low doses to stimulate flow of respiratory tract secretions.

Emetics • There are types of poisoning in which poisons may remain in

stomach for sometime before entering intestine where they may get absorbed. • Before this occurs, emetics are given to patients for physically expelling the toxic substances and reduce the harmful effects and may be able to save a patient's life.

• When a patient is in unconscious state, emetics may not be very useful and gastric lavage may be required.