The danger which attends the continual use of acids, or of alkalies, particularly of the latter, is that their long employment may engender a condition of an opposite nature to that which they were intended to alleviate. An acid may at length cause a lithic deposit in the urine; or, still more frequently, an alkali may produce a phosphatic sediment. Their administration should therefore be conducted with caution.
There are some other remedies which may be advantageously employed as solvents for Uric acid and Urates, whose use is not attended with this danger, and whose efficacy is a proof that the occurrence of a deposit in the urine is not a mere question of the preponderance of acid or of alkali in that secretion. The most important of these is the common Phosphate of Soda, first recommended by Liebig, who discovered that Uric acid was soluble in a solution of that salt.
If forty grains of dry Phosphate of Soda, seven grains of Uric acid, and fifteen of Hippuric acid, be dissolved in a pint of hot water, and to this solution two per cent. of Urea be added, a kind of artificial urine will be formed.
Biborate of Soda, or Borax, has also the power of dissolving Uric acid, and has been recommended in the treatment of lithic deposits by Bouchardat and Binswanger.
Mr. A. Ure has strongly recommended Benzoic acid in these cases. It passes out in the urine as Hippuric acid. (Vide Prop. VI.) The amount of the deposit appears to decrease under the use of this remedy, but whether the formation of the Uric acid in the blood is prevented, as supposed by Mr. Ure, or whether it is not simply held in solution by means of the Hippuric acid, is not clear. Dr. Golding Bird recommends also Cinnamic acid, which is contained in Cinnamon water, and in the balsams of Peru and Tolu. It resembles Benzoic, and undergoes the same change into Hippuric acid. The salts of these acids possess a similar power.
Diuretics in general are useful in all cases of urinary deposit, for they increase the quantity of the fluid part of the urine. It is observed by Dr. Prout that healthy urine is the best solvent that we are able to supply.
When solvent remedies are employed for the purposes above mentioned, they not unfrequently fail altogether; and, as has been already observed, they require, even when successful, to be perpetually administered, or else the deposit will recur. For the solvent passes out along with each successive quantity of the Lithic or Phosphatic matter that is formed and excreted.
A radical cure of such deposits can only be effected by a medicine that shall counteract the morbid process by which they are continually produced. This cannot be done by a Restorative, but requires a Catalytic medicine. Such remedies we must presently consider. (Vide Antiarthritics.)
Thus are concluded the six orders of restorative medicines; all of which are seen to agree together in some common characters.
When a disease depends on a want of some material in the system, then it admits of being cured by a restorative, which, in the theory of its action, is the simplest of all known medicines. And when a morbid process results in a diminution of the amount in the blood of some necessary constituent, then also may a Restorative be of use in alleviating the consequences of such a disorder; or may even effect a cure, when the morbid process has ceased, and left only its results behind it.