Physiological Action (External)

Locally applied, iodine in tincture, or strong aqueous solution, acts as an irritant or caustic. It stains yellowish brown, permeates and destroys the epidermis, and, if it reaches the true skin, causes severe heat and prickling, sometimes serous effusion and vesication, followed by desquamation or superficial scarring.

Volkmann and Schede found that, a few hours after the application of iodine, the white blood-corpuscles had escaped from the neighboring vessels to such an extent as to give, under the microscope, an appearance of suppuration; disintegration and fatty degeneration of tissue-elements also occurred, and prolonged applications to the limbs of rabbits caused periostitis. Iodine has marked antiseptic and antizymotic power, and is fatal to the lower forms of life, both animal and vegetable.

Its vapor when inhaled, undiluted and in sufficient quantity, causes heat, irritation, and cough, and sometimes has occasioned bronchitis and haemoptysis.

Frictions with iodide of potassium sometimes produce local irritation and an acneiform eruption.

It has been stated that iodoform does not cause local irritation, but I have known it to do so when applied to abraded surfaces, especially inflamed ulcers; in ordinary cases it has some anaesthetic effect.

1 Iodine may be detected in any secretions by white starched paper, which should be moistened with the liquid and then touched with nitric acid containing some nitrons acid: blue iodide of starch will be developed.

Pathological Changes

After death from iodoform, fatty degeneration has been found in the liver, kidneys, heart, and voluntary muscles. Binz attributes this to the setting free of iodine in the body.


The stimulant action of iodine is increased by warmth, alcohol, ozonic ether, the essential oils, etc. Ammonia has been especially found to assist its effect and enable it to be borne, either by chemical combination with it, or by determining free circulation in the skin.

The absorbent effect is remarkably aided by the simultaneous use of mercury, and vice versa (British Medical Journal, i., 1875).

Antagonists And Incompatibles

Cold, quinine, digitalis, the alkaline bromides, and other sedatives to the circulation, moderate or antagonize in part the specific action of iodides; this fact, however, does not prevent their combination for therapeutic purposes. Starch and albuminous substances are the best chemical antidotes to iodine in cases of poisoning.

Carbolic acid and liquor ammoniae enter into combination with the drug, and remove its brown color, but are said not to lessen its active properties. I have not, however, obtained as good curative results in absorption of tumors from the ammoniated iodine as from the pure drug. Bismuth subnitrate, which is sometimes prescribed with the iodide of potassium, precipitates an insoluble red iodide of bismuth. The organic alkaloids, strychnia, atropia, etc., are precipitated by iodine - according to Dr. Fuller, 1 1/2 gr. of strychnia by 1 dr. of tincture of iodine; hence, he and other observers have thought them mutually antidotal, but the compounds formed are themselves poisonous (Medical Times, i., 1861; Lancet, i., 1868), and require removal from the stomach as much as the original poison (Lancet, i., 1876). The iodide of starch may be antidotal to sulphides and to caustic alkalies, as stated by Bellini.

Therapeutical Action (External)

Iodine is used (both alone and combined with iodide of potassium or with camphor) in tincture, liniment, and ointment, as a mild stimulant, or strong counter-irritant, or a caustic, according to the strength of the application. It causes pain when applied freely, and in children and delicate tuberculous subjects should be used with special caution.

Preparations And Dose

Tinctura iodi contains iodine, 1/2 oz., iodide of potassium 1/4 oz., rectified spirits 20 fluid oz.: dose, 5 to 20 min. Liquor iodi contains 20 gr. iodine, 30 gr. iodide of potassium, in 1 oz. water: dose, 3 to 10 min. Linimentum iodi contains iodine 1 1/4 oz., iodide of potassium 1/2 oz., camphor 1/4 oz., rectified spirit 10 oz. Unguentum iodi: iodine 32 gr., iodide of potassium 32 gr., proof spirit 1 dr., prepared lard 2 oz. Vapor iodi (inhalation of iodine) contains tincture of iodine 1 dr., water 1 oz.; heat slightly for inhalation of vapor. Iodoformum: dose, 1/2 to 2 gr. in pill, or pastilles - as made by Messrs. Bullock, containing 2 gr. in each (Medical Times, ii., 1878). Unguentum iodoformi: 1 part in 8.

Collodium iodoformi: 1 part in 16. A suppository containing 20 gr. with cacao butter is officinal in the German Pharmacopoeia. Potassii iodidum, sodii iodidum: dose, from 1/2 to 30 gr. and upward in syphilis; average dose, 3 to 5 gr. The dose of the ammonium salt is somewhat smaller.

[Preparations, U. S. P. - Liquor iodinii compositus: iodine 360 gr., iodide of potassium 1 1/2 troyounce, distilled water 1 pint. Dose, 2 to 6 minims. Tinctura iodinii: iodine 1 troyounce, alcohol 1 pint. Dose, 1 to 10 minims. Tinctura iodinii composita: iodine 1/2 troyounce, iodide of potassium 1 troyounce, alcohol 1 pint. Dose, 5 to 15 minims. Un-guentum iodinii: iodine 20 gr., iodide of potassium 4 gr., water 6m., lard 1 troyounce. Unguentum iodinii compositum: iodine 15 gr., iodide of potassium 30 gr., water 30 m., lard 1 troyounce.


No Officinal Preparations.

Physiological Action (Internal)