Expectorants are drugs which stimulate, depress, or modify the secretion from the bronchial or laryngeal mucous membranes and promote.its expulsion.

There are many drugs not classed as expectorants which, under certain conditions, may be used to serve one of these purposes.. Thus, opium and chloral, by the depressing influence which they exert upon the respiratory center and the reflex mechanism, may relieve reflex and purposeless cough, or, as is the case with the former drug, check excessive secretion or render it more viscid.

Demulcents, such as gum acacia, flaxseed, elm, etc., and other drugs like potassium chlorate, sodium chloride, etc., either lessen or excite the tracheal and bronchial cilia, retarding or promoting expectoration of bronchial mucus. The classification usually adopted seems to be the most reasonable - viz., that of dividing expectorants into two classes: 1. Nauseant or Sedative. 2. Stimulating. Among the more important Nauseant or Sedative Expectorants l are:

*Alkalies;

*Antimony and potassium tartrate (tartar emetic);

*Apomorphine; Grindelia;

* Ipecacuanha;

* Lobelia;

* Pilocarpus;

* Potassium iodide;

* Quebracho;

all of which are considered in detail elsewhere.

The important Stimulating Expectorants are:

*Acids;

*Ammonium carbonate; Ammonium chloride;

*Balsam of Peru;

*Balsam of Tolu;

*Benzoin and benzoic acid;

*Copaiba;

*Cubeb;

* Garlic; Licorice;

*Nux vomica (Strychnine);

*Oil of Scotch fir (oleum pini sylvestris);

* Oleum pini pumilionis;

*Onion;

*Saccharine substances; Sanguinaria;

*Senega (saponin);

*Sulphur;

*Squill;

*Tar;

*Terebene;

*Terpin hydrate;

*Turpentine;

*Volatile oils in general.

1 (Those marked with an asterisk (*) are elsewhere given in detail.)

As a rule, Sedative Expectorants are permissible only in acute stages of bronchitis, when, as in the case in the beginning of all catarrhal inflammations, there is complete or partial suspension of function, absence of secretion, and much irritation in the bronchi, with distressing, harsh, and dry cough.

In these conditions of the respiratory passages the nauseating sedative expectorants serve a useful purpose in lowering arterial tension, lessening the blood-supply to the inflamed parts, and increasing the secretion of mucus.

In sufficiently large doses to produce emesis the same expectorants are frequently employed to expel an accumulation of mucus mechanically by the act of vomiting.

Stimulating expectorants are more serviceable in chronic and relaxed conditions of the mucous membrane. They are usually employed to diminish or disinfect an abnormally increased secretion. These remedies generally increase blood-pressure and facilitate expectoration, being eliminated to a great extent by the mucous membranes which they stimulate.

The alkalies are especially useful in lessening the viscidity of mucus, rendering it more fluid, less tenacious, and therefore more easily expelled.

It requires considerable skill to combine expectorants so as to best suit the various conditions found in practice. The diseases of the respiratory passages gradually merge, so that in the treatment of them it is often difficult to decide which remedy will be of more service, a sedative or a stimulant expectorant. The physician should carefully examine each individual case and decide whether he wishes to diminish or increase the blood-supply to the respiratory tract; to stimulate or depress the respirations; to overcome spasm of the bronchial muscles; to diminish, increase, or disinfect the bronchial secretion.

A thorough knowledge of the patient's condition and of the physiological action of the various remedies at command will enable the observant practitioner to combine expectorants in such manner as to yield ordinarily highly satisfactory results.