Definition of Diuretic:
Diuretics (Gr. through, + to urinate) increase renal secretion, either by raising the local or general blood-pressure, thereby increasing renal circulation (blood-supply), or by stimulating the secreting cells or nerves of the kidneys, or by washing out the kidneys with much water taken at night or early morning;
- Refrigerant - which excite the renal epithelium, producing a hyperemic condition of the kidneys and an increased amount of water in the urine; they depress the heart and general circulation: potassium acetate, citrate and bitartrate, ammonium and sodium acetates, lithium carbonate and citrate, magnesium citrate and sulfate, water, milk, cold applications;
- Hydragogue - which largely increase the amount of water in the urine, owing to raising arterial pressure, locally or generally: digitalis, strophanthus, spirit of ethyl nitrite, nitrites, squill, cimicifuga, scoparius;
- Stimulant (blennorrhetics) - which act directly upon the renal tissue, by which they are to a great extent eliminated from the body: buchu, copaiba, cubeb, matico, pareira, uva ursi, savin, juniper, chimaphila, taraxacum; cantharides, turpentine, oil of santal, corn silk, apocynum [Culbreth1927, pg 44].
See also Aquaretic, which is similar to a hydrogogue, but binds to vasopressin receptors in the renal collecting duct, promoting excretion of solute-free water [ORWJr; Saunders2007].
Diuretics are medicines which increase the flow of urine by their action upon the kidneys [Brown1878; Meyer1932].
A remedy that provokes an increase in the flow of urine. Some plant materials are excreted via the kidneys and act osmotically to bring more water with them. Others may reduce the reabsorption of water from the kidneys. Used to reduce problems of urinary infections and urinary stones, to increase loss of water in oedamatous problems and as part of an eliminatory program [Sanchez BOTM680].
Increases flow of urine [Palmer2004].
See [Yarnell2002] for a discussion of possible mechanisms of action.
Botanical diuretics
Numerous herbs are traditionally considered diuretic (see Table 1). Preliminary clinical trials have shown that
various herbs increase urinary output both in healthy people and people with urologic disease, and they continue to be widely prescribed in Europe [32, 45, 52].
Other trials have failed to confirm a diuretic effect in healthy people [11]. None of these herbs have been associated with serious adverse effects. More research is warranted on those agents shown effective to date to determine if they continue to show benefits in more rigorous settings.
No trials have definitely proven the mechanism of action of diuretic herbs in humans. The late pharmacognocist Varro Tyler, PhD, theorized that herbs act only as aquaretics, or agents that increase water excretion without affecting renal handling of electrolytes [66].
Aquaretics may work by causing dilation of glomerular arterioles, thereby increasing glomerular filtration rate.
Since water intake can itself have aquaretic effects, and many aquaretic herbs are taken as teas, this would partially explain variable results of clinical trials with aquaretic herbs [46, 47].
Existing animal data do not support the aquaretic theory, however. Repeatedly, diuretic herbs have been shown to influence renal electrolyte handling, particularly sodium and potassium, and thus have diuretic activity [14, 44]. The distinction between an aquaretic and diuretic is critical. Aquaretics are very unlikely to affect edema or hypertension since sodium chloride is the major determinant of extracellular fluid volume and aquaretics do not influence electrolyte levels. At least one human trial has also shown that a diuretic herb,
Urtica dioica (stinging nettle) folium, can reduce blood pressure in patients with congestive heart failure, an effect incompatible with the hypothesis that stinging nettle is only aquaretic [26].
It should be noted that there are three other categories of botanical diuretics:
(see Table 2). Few of these plants are used primarily as diuretics, however, as their other properties are either more important or strong (in the case of cardiac glycosides and methylxanthines) or the effects are too weak or poorly investigated (in the case of botanical ACE inhibitors). Therefore, these are included mostly for reference but are not used as diuretics. In the case of cardiac glycosides, the diuretic effect may indeed contribute to their benefit in patients with congestive heart failure.
- plants containing cardiac glycosides: Used for CHF patients exclusively, and largely superseded by synthetic drugs:
- Digitalis purpurea L (digitalis) folium
- Nerium oleander L (oleander) folium
- Apocynum cannabinum L (Indian hemp) folium
- Adonis vernalis L (spring adonis) flosa [endangered]
- Urginea maritima (L) Baker (red squill) bulbus
- Convallaria majalis L (lily-of-the-valley) herba
- plants with angiotensin-converting enzyme (ACE) inhibiting properties. Have only been proven to act in this way in vitro at present:
- Allium sativum L (garlic) bulbus
- Camellia sinensis L (tea) folium
- Crataegus laevigata (Poir) DC (hawthorn) fructus, flos, & folium
- Ganoderma lucium (Curtis Fr) P Karst (reishi) fruiting body
- Olea europaea L (olive) folium
- plants containing methylxanthines. Rarely used in this way due to adverse effects (anxiety, insomnia, cystic breasts, etc.):
- Camellia sinensis
- Coffea arabica L (coffee) semen
- Paullinia cupana Kunth (guaraná) folium
- Cola nitida (Vent) A Chev (cola) semen