Sodium Chloride, in dilute solution, causes the tissues to become swollen and softened; whereas, in concentrated solutions, it tends to extract water from the tissues. Consequently, the red blood-corpuscles become swollen when in hypotonic solutions, and shrink in hypertonic solutions. This same characteristic action of sodium chloride on muscle tends to injure the vitality of the muscle-cell, and on mucous membranes tends to interfere with function. The blood is concentrated by hypertonic solutions, and made more liquid by hypotonic solutions, though in either case normal conditions are soon restored by osmosis of tissue-lymph.
Salt solutions in the blood augment the flow of urine through increased capillary pressure in the glomerulus.
Salt solution, in the isotonic form, 0.9%, is used chiefly to compensate for loss of blood, as in hemorrhages and in cholera; and for flushing the system in uraemia.
Potassium Chloride depresses the central nervous system, especially the great centers in the medulla; it also has a toxic action on the heart.
Potassium Salts are not to be administered for the potassium effect, as this effect is not elicited when the drug is given by stomach.
Ammonium Chloride, when injected subcutaneously or intravenously, stimulates the central nervous system in the same manner as strychnine, but this action is not elicited by oral administration. When given by mouth, it is absorbed readily by the stomach and intestines, and has been thought to stimulate the mucosa of the stomach and intestines. In the bronchi, however, application must be made direct, as the epithelium of the lungs is impermeable to the ammonium ion.
Ammonium chloride is thought to be good for gastric catarrh; and, in the form of nascent vapor, is used for bronchitis.
Ammonia Gas, when inhaled, irritates the nasal and bronchial mucosa, producing thereby a reflex stimulation of the vasomotor center, with a resulting vasoconstrictor action and a temporary rise in blood-pressure. It is thus of value in syncope. The inhalation is dangerous in higher concentration than 1: 2000.
Ammonium Carbonate is a mild irritant to the stomach. When given in solution it is thought to be of value in the treatment of flatulency.
The ammonia vapor from the carbonate is used in "smelling salts" for its reflex stimulation. It is probably of some use in impending attacks of faintness.
Ammonia salts are rapidly excreted.