This section is from the book "Materia Medica And Therapeutics Inorganic Substances", by Charles D. F. Phillips. Also available from Amazon: Materia medica and therapeutics.
The alkaline bromides are readily absorbed, and have been found in the urine and saliva five minutes after a dose of 15 gr. (Rabuteau); in ten minutes' time the reactions were very manifest. Bowditch drew blood from the carotid of an animal six minutes after 10 gr. had been taken, and calculated that even in that time a third of the dose had passed into the circulation (Boston Journal, October, 1868). They are usually eliminated unchanged, and Voisin has obtained cubical crystals of the potassium salt from the urine of patients taking it. The rate of elimination varies. In some experiments already mentioned, the urine gave traces of the drug in ten minutes; in others thirty minutes was the earliest period, in others twenty-five hours (Bow-ditch). The excretion of single large doses is usually complete in one or two days (Chauvet, Amory), though minute quantities have been detected in the urine for three or four weeks afterward (Rabuteau). If the drug has been taken continuously for some time, the period of its excretion is prolonged: thus Namias found it continue for fourteen days (Gazette Hebdomadaire, 1868), and renal disease so far impedes its excretion that upwards of thirty days may be required for its completion. Dr. Stevenson "detected bromides in the urine of a child, passed about four weeks after the medicine was discontinued" (Lees: "Pathological Society's Transactions," 1877).
As evidence, also, of the slow elimination of these salts, Drs. Crocker, Lees, Barlow, myself and others, have noted the increase, or even the chief development, of the rash sometimes produced by them after the discontinuance of the drugs. The elimination of bromides is certainly slower than that of iodides. It occurs not only by the kidneys and the saliva, but also by the mammary, lachrymal, and sudoriparous glands, and by mucous membranes - by the last especially in the case of the ammonium salts. In exceptional instances the salts have been decomposed in the system and free bromine eliminated in the breath. The alkaline compounds do not usually pass by the faeces unless diarrhoea occur; but, if metallic bromides be taken, the metal passes chiefly by the bile and the motions.
Thus, when experimenting with bromide of iron, Namias found bromine abundantly in the urine, but iron scarcely at all. The same observer, examining the body of a man who died while taking bromide of potassium, found that salt in all the fluids, as well as in the brain, liver, lungs, and other viscera (Comptes Rendus, tome lxx.). After very large doses, an unabsorbed portion has been found in the intestine.