They may operate in four ways - 1, as direct stimulants to the kidneys, by being absorbed into the circulation, and passing unchanged to them; 2, by undergoing decomposition in transitu, and acting on the kidneys by one or more of their constituents; 3, by acting primarily on the stomach and primAe viAe, and sympathetically on the kidneys; 4, By Stimulating The Disordered Capillary System To A More Healthy Action. The objects for which they are administered, - 1, to restore a natural amount of urine, when, from any cause, it has been diminished; 2, to promote the elimination of any acrid or poisonous matter from the system; 3, to relieve inflammatory action; 4, to promote the absorption of dropsical effusions;

5, to augment the elimination of water, and thereby to enable the urine to keep in solution the solid constituents of this secretion, as well as to act as a solvent for calculi contained in the urinary organs;* 6, to act as derivatives in diseases of the heart; 7, as evacuants in fever.

Their operation is promoted - 1, by the previous employment of depletion and antiphlogistic remedies, if the patient be not already too much debilitated; 2, by drinking plentifully of diluents, particularly when salines have been employed;

3, by avoiding all agents which cause perspiration or purging;

4, by remaining in a cool and equal temperature; 5, by a combination with other remedies of the same class. N.B. Certain passions, particularly fear, increase the urinary secretion. Even under the most favourable circumstances, diuretics are very uncertain in their operation.

Their action is impeded - 1, by Opium; 2, by the use of diaphoretics and cathartics; 3, by abstinence from diluents. The period of the day best suited for their administration is the daytime, the patient remaining out of bed during their operation.

* Pereira, vol. i.

3060. Therapeutic Uses

Anasarca, Ascites, and Dropsical Affections generally, much improve under copious diuresis. "When the patient is strong, or not debilitated by long previous illness, the abstraction of blood should precede the use of diuretics; by this means their efficacy and operation are greatly increased. In passive dropsies, it is often advantageous to combine diuretics with tonics and mild stimulants. In Dropsy connected with Disease of the Heart, especially when accompanied by a scanty secretion of high-coloured urine, diuretics prove of the highest service. In most cases, the dyspna, palpitation, cough, &c., decrease in the same proportion that the urine increases, and the dropsy disappears. Digitalis, Pulv. ScillAe, and Potas. Bitart. are excellent diuretics in these cases. (Dr. Hope.)

3061. In Inflammatory Dropsy, Attendant On Granular Disease Of The Kidney, Drs

Bright, Osborne, Watson, and others, condemn the use of diuretics, particularly those of a stimulating nature; but Dr. Christison* considers that they may be used without any risk of aggravating the primary disease, and that hydropic effusions cannot, in general, be so efficiently removed in any other way. He advises the following formula: -

3061 In Inflammatory Dropsy Attendant On Granular  254 Pulv. Digitalis gr. j. - ij., Potass. Bitart. 3j. - 3ij., M. ter in die ex aq. Dropsies are occasionally removed by the endermic use of diuretics.

3062. In Valvular Disease Of The Heart, Dr

Hope remarks that diuretics are remarkably beneficial in every stage; for, by drawing off the serous portions of the blood, they diminish the quantity, without deteriorating the quality of that fluid, and thus relieve palpitation and dyspnoea, and obviate infiltration, without materially reducing the strength.

3063. In Hypertrophy Of The Heart, Dr

Hope found the most decided advantage result, in severe cases, from diuretics; not only when there was dropsy, but when this state was absent. They act as powerful derivatives.

3064. In Puerperal Fever, Dr

Murphy§ states that he has found diuretics, particularly the Nitrate of Potash, very efficient as evacuants in this disease. The kidneys, in this case, act as the outlet for the poison in the blood.

3065. In Inflammation, diuretics are sometimes required, not merely on account of any derivation from the seat of disease thereby procured, but with the view of reducing whatever serous plethora may exist, and of removing from the circulation those ultimate products of assimilation which are liable to accumulate in the blood, to an injurious extent, during the febrile state, and thereby to heighten the local affection. The refrigerant diuretics, as Sp. Ether. Nit., Potas. Bitart., &c., should be employed for this object. (Dr. Copland.*)

* Lib. of Med., vol. iv. p. 293.

On Diseases of the Heart, p. 408.

Ibid., p. 287.

§ Med. Gaz., Jan. 28, 1850.