External

These salts when applied to the broken skin or an ulcerated surface, are all astringents, acting by precipitating the albumin in the discharge and also that in the tissues. Thus they resemble lead and silver salts, but as a whole they are less powerfully astringent. The most active of them are the sulphate and acetate, whilst the precipitated carbonate and oxide are very weak. All these zinc salts are mild haemostatics.

Internal

Alimentary canal. - They all have an astringent effect on the gastric and intestinal mucous membranes. The sulphate, and to a less degree the precipitated carbonate, in doses of about 20 gr. 1.20 gm. are prompt emetics. They act directly on the stomach, and have the advantage of producing very little depression.

Remote Effects

Nothing is known about the remote action of zinc salts, nor do we know how they act on the blood. It has been stated that they are depressant to the nervous system as a whole, and that they act as remote astringents, and will therefore arrest haemorrhage from the uterus, kidney, etc., but this statement is probably incorrect. The prolonged administration of zinc salts causes symptoms like those of lead poisoning. Probably the symptoms of which those who work with zinc sometimes complain are due to arsenic and other metals which contaminate zinc compounds.

Therapeutics of Zinc Salts

External

A solution of the sulphate, generally about 1 to 240, usually colored red with compound tincture of lavender, and then called Lotio Rubra, is very often applied for its astringent effect to all sorts of raw surfaces and ulcers, and as an injection in gonorrhoea, leucorrhoea, vulvitis or otitis. Plain solutions of this strength may be applied to the eye for conjunctivitis. The oleate is an excellent application to sores and ulcers when a less astringent preparation is required; and the oxide and precipitated carbonate, either dusted on the part or used as an ointment, are in constant use for cases in which only a mild astringent effect is desirable. An ointment, often known as Unguentum Metallorum, consists of equal parts of ointments of zinc oxide, lead acetate, and diluted mercuric nitrate. This is a very good application for many varieties of eczema, sores and ulcers. Equal parts of zinc oleate, mercuric oleate and diachylon ointment (see p. 166) form an ointment which has the great advantage of being transparent, and therefore the progress of the disease can be observed, without washing off the ointment. Calamine (purified zinc carbonate) is an excellent slight astringent for skin diseases. An ointment (1 to 5 of ben-zoinated lard) or a lotion (calamine, 3; zinc oxide, 3; lime water, 16; glycerin, 4; water, 160;) are good preparations. The following often succeeds in pruritus: Zinc oxide, 25; gelatin, 20; glycerin, 60; water to 480. The jelly is to be melted when used, and applied with a brush, and then covered with cotton.

Internal

Alimentary canal. - On account of their disagreeable taste, solutions of zinc salts are not used as astringents to the mouth. Small doses of the oxide or sulphate may be given as astringents in diarrhoea. The sulphate is a very good emetic for cases of poisoning, for it acts promptly without causing much nausea and hardly any depression. It is occasionally given as an emetic to children suffering from laryngitis or bronchitis.

Remote Effects

Because it is believed to act as a depressant to the nervous system, zinc sulphate has been given in hysteria, epilepsy, whooping-cough and chorea in doses of 1 to 3 gr. .06 to .20 gm. thrice a day. Its use is now generally limited to chorea, but often its effect is so slow that it is difficult to prove that the patient would not have improved quite as rapidly without any drug. It is usually said to be a tonic, but there is no trustworthy evidence for this statement. The oxide Trousseau's pill (5 gr.; .30 gm. of zinc oxide with 1 gr.; .06 gm. of extract of hyoscyamus), given internally will occasionally check the night-sweats of phthisis but it is quite likely to interfere with the digestion.

Toxicology

Symptoms

Zinc Chloride is a corrosive irritant poison, causing a sensation of burning in the mouth and throat, abdominal pain, vomiting - the vomit containing blood, mucus, and shreds of mucous membrane, - violent purging, and collapse. Zinc Sulphate, in large doses, acts as an irritant poison producing vomiting, colicky pains, diarrhoea and prostration. Post-mortem. - The appearances are those produced by an acute irritant.

Treatment

Wash out the stomach, or give emetics (see p. 139), and then demulcents; lime water, mucilaginous drinks, and albumin freely in the form of eggs or milk.