Absorption And Elimination

Ammonia and its carbonate are not wholly absorbed as such - a part becomes changed into chloride in the stomach (Rabuteau). Most of the free ammonia combines with carbonic acid in the organism (Bellini: British Medical Journal, i., 1874). Salts of ammonia with organic acids (citrate, etc.) are decomposed in the capillaries, when the acids are oxidized and ammonia is set free. Compounds of ammonia with mineral acids form alkaline salts at the expense of carbonates in the blood (Bellini).

Though Lange did not find ammonia in the air expired by animals taking it (Archiv fur Exper. Path., Bd. ii.), other observers have often done so, and Bellini concluded that caustic ammonia and the carbonate, when taken in small doses, were entirely and very quickly eliminated by the lungs; of large doses, some passed also by other channels. Whatever salt was taken, carbonate was eliminated by the lungs.

There is sufficient evidence that the carbonate, when taken in moderate or even large doses, is not excreted as such by the kidneys. Rabuteau, took 60 gr. daily for five days without finding any in the urine, which continued acid, whereas a mere trace of ammonia added directly to the urine suffices to give an alkaline reaction. Dr. Bence Jones had previously pointed out this continued acidity of urine under ammonia, and suggested that the drug becomes so far oxidized in the system as to give rise to nitrous or nitric acid, which appears in that secretion ("Philosophical Transactions," 1851, and Medical Times, ii., 1854). Only after very large doses (160 gr. daily) some carbonate of ammonia is eliminated in the urine, which then becomes alkaline, and deposits ammonio-magnesian phosphate.

Ammonium chloride does not readily decompose in the system; it is excreted by the urine and partly by the saliva (Rabuteau); a small quantity passes out by the skin.

Frerichs taught that in uraemia an unusual amount of ammonia carbonate (arising from decomposition of urea) circulated in the blood and was excreted by the lungs, and, although some doubt has been thrown upon this by Dr. George Johnson and others (Medical Times, i., 1858), it certainly occurs in some cases (cf. p. 256). Richardson has pointed out that during an actual attack of uraemic convulsion, the amount of ammonia excreted is less than at other times on account of the retention of urea in the system (Lancet, ii., 1860). Gull found ammonia, when the albumen in the urine was not large in amount (Medical Times, i., 1861, p. 616). Uraemic coma is, however, connected with the circulation of urea, etc., rather than of ammonia (Medical Times, i., 1862).

Physiological Action (External)

The vapor of carbonate of ammonia (smelling salts) is stimulant and slightly irritant, that of the strong ammonia is intensely irritant to the whole of the air-passages and conjunctivae, and has even caused fatal bronchitis. Liquid ammonia is also a strong local irritant; diluted with oil it is "rubefacient," but applied in strength, and evaporation prevented, it vesicates, and if injected under the skin causes severe sloughing. Oertel reported that the direct application of liquor ammoniae to the air-passages caused a membranous effusion similar to that of croup; but very careful observations by Meyer on the same point verified only a local catarrhal inflammation and hemorrhage (British Medical Journal, ii., 1874). Ammoniacal urine commonly irritates the bladder.

Ammonia has marked antiseptic powers: 1 dr. of liq. ammon. fort. on lint under a bell-jar preserves morbid specimens, and the same quantity with water preserves them better than spirit.

Physiological Action (Internal)

Circulatory System

Medicinal doses of ammonia and its compounds quicken the heart's action and capillary circulation, but only for a comparatively short time: such stimulation is not always marked in healthy persons - it is more evident in the weak and in invalids: there is increased sense of warmth, the face becomes flushed, the eyes more brilliant, and the mental condition stimulated.

Ten drops of the liquor, diluted with 1 or 2 oz. of warm water and injected into a vein, excite the heart so powerfully as to rouse a patient from a state of collapse (Tibbitts: Medical Times, ii., 1872). Larger quantities - 30 drops - given in the same manner, after a momentary arrest, stimulate intensely, and may induce convulsion: still larger quantities cause momentary fall of arterial pressure, then sudden and enormous rise, with corresponding increase of pulse-rate: this result occurs equally after division of the cord, hence it is not due to stimulation of the vaso-motor centre, but of the accelerator nerves of the heart (Lange).

On the other hand, according to Rabuteau, 40 grs. of carbonate, dissolved and injected into a vein, weaken the cardiac contractions and render them irregular, while 60 gr. cause a sudden arrest of the circulation, the heart-muscle being paralyzed.

The corpuscles are altered by toxic doses; they cease to contain the normal quantity of oxygen, and do not absorb it even when shaken up with the gas (Feltz and Ritter).

The continued use of ammonia salts causes similar toxic effects; the pulse becomes very feeble, and the corpuscles pale and wasted, as after typhoid fever; this is but the recognized effect of all alkalies. These results are reported by Cazenave (Bulletin de Therapeutique, t. xxxi.), yet Pereira has given 15 gr. thrice daily for two months without apparent injury, and often a scruple thrice daily for two or three weeks.

Ammonia or its carbonate added to blood outside the body renders it or keeps it fluid, and, when given internally, exerts an influence in the same direction; Dr. Richardson even thinks they have sometimes caused disintegration of clot already formed in the vessels (v. p. 259). Coagulation of blood is not, however, due to escape of ammonia, as thought probable at one time, nor will ammonia always or wholly prevent it. A difference in time of coagulation was the only difference observed by Rabuteau in experiments on dogs, for while coagulation of their blood usually occurs in two minutes after withdrawal, it occurred only in ten minutes when 60 gr. of ammonia carbonate had been injected: the clot, however, was firm and resistant.

Chloride of ammonium delays coagulation of blood, and when added to it with access of air renders or keeps it red, as do other chlorides.