1. Drugs increasing the quantity of urine secreted. - These are called diuretics. The kidney is a double organ with two distinct varieties of epithelium; it is particularly well supplied with vessels and vaso-motor nerves, and is also profoundly under the influence of variations in the quantity of blood flowing through it; hence it is, with our present state of knowledge, impossible to say how many diuretics act, but the following table modified, from Brunton's work, shows the various ways in which they probably act, many in more ways than one:

Raise arterial . pressure

Generally

. . . .

Increased cardiac action

Digitalis,

Caffeine,

Alcohol,

Strophanthus,

Sparteine,

General vascular contraction

Erythrophloeum,

Digitalis,

Squill,

Convallaria,

Strychnine,

Cold to skin.

Locally in kidney

- Contract efferent vessels

Act on vaso-motor centres

? same as above.

Locally on kidney.

Broom, Caffeine (large doses), Buchu, Uva ursi, Juniper, Turpentine, Copaiba, Cantharides.

Dilate, chiefly locally, renal vessels

Act on secreting nerves or renal cells

Caffeine, Urea.

Increase water excreted . .

Urea,

Caffeine,

Theobromine Sodio-salicylate, Calomel,

Increase water and solids excreted

Colchicum, Liquor Potassae, Potassium Acetate, Potassium Citrate, Potassium Nitrate, Sodium Citrate and other salines.

Therapeutics

Diuretics are used in cardiac and pulmonary diseases when, owing to the general vascular disturbance, the quantity of urine falls below the normal standard. Also, in diseases in which there is excess of fluid in certain parts of the body; for example, pleuritic effusion and ascites, with the object of getting rid of as much fluid as possible by the kidneys. Also, they may be used to dilute the urine, e.g., when it is prone to deposit its solids. Lastly, in certain forms of kidney disease, although in these maladies it is always a question how far it is desirable to stimulate diseased organs. It is of great importance to remember that diuretics may act in many different ways; that there are many causes for diminution in the quantity of urine secreted, and that it is difficult to say in any particular case what is the cause of the decrease in the quantity secreted. Therefore, it is usual to give diuretics in combination, in the hope that if one of them does not have the desired result another will.

2. Drugs diminishing the quantity of urine secreted. - These are such as produce acute inflammation of the kidney when given in large doses; e.g., turpentine, cantharides, phosphorus. Ex-algin is reputed to diminish the quantity of urine. They are never given for this purpose in medicine.

3. Drugs rendering the urine acid. - There is one drug that can do this, and that is benzoic acid, for in its passage through the kidney it is converted into hippuric acid. Benzoic acid is, therefore, given when from any cause the urine undergoes alkaline decomposition anywhere within the urinary passages. Salicylic acid will, to a slight extent, increase the acidity of the urine, as will very large doses of citric acid, tartaric acid borax, and possibly saccharin. The free use of carbonated water also increases the urinary acidity (Ultzmann). Urotropin is the most reliable remedy to render an alkaline urine acid.

4. Drugs which render the urine alkaline.- -Some salts of the metals, potassium, sodium, lithium, calcium, will do this e.g., the carbonates, borates and hydroxides; even the tartrates, citrates, malates, lactates, and acetates, for they escape by the kidney as carbonates. Nitric acid is said to increase the amount of ammonia in the urine, and thus to render it slightly alkaline. Ammonium salts given internally do not render the urine alkaline, because they are decomposed in the body, urea being probably formed; they may even increase the acidity from the larger amount of nitric acid excreted.

Lithontriptics are drugs which prevent the decomposition, in the urinary passages, of the solids of the urine. If this fluid be acid, uric acid often crystallizes out, forming gravel or uric acid calculus; less often lime oxalate crystallizes, giving rise to lime oxalate calculus. When there is any likelihood of the formation of either of these calculi, alkalies should be given. If the urine is undergoing alkaline decomposition phosphates are liable to crystallize out. In this case the object will be to render the urine acid and aseptic. This will be attained by giving benzoic acid or benzoates, salicylic acid or the salicylates, uro-tropin, or the other urinary antiseptics.

Therapeutics

The chief use of alkalies is to diminish the acidity of the urine, so as to render the precipitation of uric acid unlikely; or to render it alkaline, so as to attempt to dissolve a uric acid calculus. We know of no drug which will dissolve a lime oxalate calculus. Alkalies are also given to gouty subjects, partly to alkalize the blood, but also partly to alkalize the urine, for such persons are very prone to deposit uric acid in the urine. Potassium urate is much more soluble than sodium urate, and lithium urate is perhaps even more soluble; citrates and acetates are not likely to upset the digestion, consequently the drugs most used are the potassium and lithium citrates. Copious draughts of water, by diluting the urine, aid in preventing the deposition of uric acid or lime oxalate calculi. Natural alkaline waters are largely used especially those containing lithium.

5. Drugs preventing the urine from decomposing. - If the urine is retained in the bladder by stricture or from any other cause, it will undergo alkaline decomposition, and the same result may be brought about by the admixture of pus with the urine. This is generally due to inflammation of the pelvis of the kidney or the bladder. This decomposition of the urine may be prevented by giving drugs which in their excretion by the urine render it aseptic. Such are -

(1) Urotropin.

(2) Benzoic acid.

(3) Salicylic acid.

(4) Uva Ursi.

(5) Copaiba.

(6) Cubeb.

(7) Oil of Sandal Wood.

(8) Saccharin.

(9) Many volatile oils. (10) Boric acid.

6. Drugs altering the composition of the urine.-Almost any drug will do this, either because it is excreted in the urine, or

7O Pharmacology And Therapeutics.

because it sets up some changes in the body, the products of which are excreted in the urine; but here we shall only refer to certain striking ones.

Turpentine, cantharides and salicylic acid in large doses will cause blood to appear in the urine, because they set up inflammation of the kidney.

Potassium chlorate, all nitrites, acetanilid, pyrogallic acid, poisoning by the mushroom, (Helvetia esculenta) and transfusion of animal's blood, break up red blood-corpuscles, and the products are excreted by the urine rendering it dark. Large doses of mineral acids, arsenic, naphtol and naphtalin are said occasionally to produce the same result.

Phosphorus in large doses causes leucin and tyrosin to appear in the urine, and the urea is greatly increased.

The saline diuretics increase the solids of the urine.

The chrysophanic acid in rhubarb and senna makes the urine, if it is acid, a brownish color; if it is alkaline, a purplish red. Logwood renders alkaline urine reddish or violet Santonin colors acid urine yellow or greenish-yellow, and alkaline urine, reddish. Carbolic acid, naphtalin, creosote and other preparations of tar, as well as the arbutin in uva ursi, chimaphila and gaul-theria make it dark greenish-brown. Picric acid makes it a bright yellow, and methyl violet a dark blue. The urine of persons poisoned with carbonic oxide remains sweet for months.

Poisoning by carbonic oxide, curare, amyl nitrite and turpentine, and sometimes chloroform, camphor, mercury, morphine, chloral, hydrocyanic acid, sulphuric acid, alcohol, lead compounds, and salicylic acid lead to the appearance in the urine of a body which like sugar reduces Fehling' s copper solution. Some authorities state that the urine, after the administration of these drugs, does not contain glucose, but glycuronic acid; for although it reduces blue copper solutions, it does not undergo alcoholic fermentation on the addition of yeast or give the phenyl-hydrazin test. The administration of phloridzin, a glucoside from the bark of stem and root of the apple, pear, plum and cherry, which, when continuously heated with dilute mineral acids, is resolved into glucose and phloretin, leads to the production of genuine glucose in the urine.

Other drugs cause a peculiar odor in the urine; for example, the smell of violets is produced by turpentine. The aromatic odor of cubeb and copaiba can be detected in the urine after the administration of these bodies.

Lead, if taken for long periods, produces chronic interstitial inflammation of the kidney. It is stated that rarely mercury will do the same.

7. Drugs acting on the bladder and urethra. - The only ones of any practical value are sedatives to the urinary tract.

If the urine is decomposing, drugs preventing its decomposition come tinder this head. Other sedatives are opium, belladonna, hyoscyamus, pareira, buchu and uva ursi, which are direct sedatives to the vesical and urethral mucous membrane. If the urine is excessively acid, alkalies are urinary sedatives.

Urinary sedatives are used very largely in cases of cystitis and urethritis, whatever the cause may be. Local astringent and antiseptic injections are also employed.