(See also Kofein, Teobromin, Teofillin, Eufillin, Ammonium chloride.)
Diuretics, or diuretics, call the substances causing increase in removal from an organism of urine and reduction of content of liquid in fabrics and serous cavities of an organism.
Earlier diuretics applied mainly in the diseases which are followed by a liquid delay in an organism, especially in a chronic circulatory unefficiency, a nephrotic syndrome, cirrhosis. Now widely use them also in a hypertension, glaucoma and other diseases.
Therapeutic effect of diuretics is not always caused by strengthening of a diuresis, nevertheless the diuretic effect is their main pharmacological sign.
Strengthening of a mocheotdeleniye caused by diuretics is connected with their specific action on kidneys which is first of all in braking of a reabsorption of ions of sodium in renal tubules that is followed by reduction of a reabsorption of water.
Modern diuretics divide generally into 3 groups: c) saluretics, b) kaliysberegayushchy and c) osmotic diuretics. Tiazidovy and tiazidopodobny drugs (a dichlothiazide, Cyclomethiazidum, Oxodolinum, etc.), derivatives of sulfamoylanthranilic and dichlorophenoxyacetic acids (furosemide, Acidum etacrynicum, etc.), inhibitors of a karboangidraza (Diacarbum) belong to saluretics (there are also other classifications of diuretic means).
Drugs of this group render diuretic action, various on force and duration, that depends mainly on their physical and chemical properties and influence on different sites of nephron.
Tiazida (petrolthiadiazine derivatives) affect mainly a cortical segment of a nephronic loop and cause the strengthened removal of ions of sodium and potassium. Characteristic side effect of diuretics of this group is the hypopotassemia which is followed by weakness, dizziness, a headache, nausea, changes of the ECG.
Duration of diuretic action is significantly various at different drugs. So, the effect after single dose of a dichlothiazide proceeds several hours, and after intake of Oxodolinum - up to 3 days.
Tiazida widely apply at treatment of chronic heart failure. Increasing a diuresis, they reduce the volume of the circulating plasma and respectively venous return of blood to heart and load of a myocardium, reduce developments of stagnation in lungs.
Tiazida widely appoint also in a hypertension. Their antihypertensive effect is partially connected with removal of salts and waters from an organism and reduction of volume of the circulating plasma. Besides, they have direct spasmolytic effect on walls of vessels. It is established that under the influence of derivatives of a petrolthiadiazine exchange processes in cellular membranes of arterioles, in particular extraction of sodium ions from them change that leads to reduction of swelling and decrease in peripheric resistance of vessels. It is possible that at the same time not absolute lowering of maintenance of Na B + plays a role in walls of vessels, and change of a ratio between it inside - and extracellular contents.
Under the influence of tiazid the reactivity of the vascular system changes, pressor reactions to vasoconstrictive substances decrease (adrenaline, etc.) and depressory reaction on ganglioblokiruyushchy means amplifies.
The most powerful saluretics are so-called loopback diuretics which treat furosemide, bufenoks, Acidum etacrynicum. They act throughout the ascending department of a nephronic loop (Henle's loop) and sharply oppress a reabsorption of ions of chlorine and sodium. They strengthen also vydeleiy potassium ions. Saluretics are widely applied at treatment of chronic heart failure and hypertension. Due to the strong and quickly occurring their effect began to appoint also at treatment of an acute heart failure. However it is necessary to consider that the electrolytic shifts caused by them can lead to development of arrhythmias, and the plentiful diuresis can cause reduction of warm emission and arterial hypotension. In this regard, in an acute heart failure, especially in a myocardial infarction, prefer to use peripheral vazodilatator.
At use of tiazid for treatment of a hypertension it is necessary to consider that they stimulate renin-angiotenzinovuyu a system and products of Aldosteronum, leading to gradual easing of diuretic and hypotensive effect. For antihypertensive therapy it is reasonable to use drugs of slower and long action as they influence renin-angiotenzinovuyu a system more weakly and their hypotensive effect remains longer.
For stimulation reduction renin-angiotenzinovoy of a system is recommended to combine tiazida with Ab - adrenoblockers (see Anaprilin). For reduction of the side effects connected with a hypopotassemia use the combined drugs containing tiazidovy and kaliysberegayushchy diuretics (see Triamterenum, Amiloride).
The main representative of diuretics - inhibitors of a karboangidraza is Diacarbum. It reduces a reabsorption of sodium of bicarbonate and secretion of ions of hydrogen in proximal tubules and increases removal with urine of bicarbonates and phosphates. Due to short and rather weak diuretic action recently it is rather seldom applied as independent diuretic. Sometimes it is used in a combination with other diuretics for prevention of an alkalosis.
Inhibitors of a karboangidraza reduce secretion of watery moisture of an eye; they are widely applied to decrease in intraocular pressure in glaucoma.
Sometimes they are appointed as additional resources at treatment of epilepsy, especially small forms.
Kaliysberegayushchy diuretics increase discharge of ions of sodium and reduce at the same time discharge of potassium ions. They act in distal tubules in places where ions of sodium and potassium exchange; have less strong diuretic effect, than saluretics, but do not cause a hypopotassemia. As antipotassiumuretic means them can be used first of all in a combination with saluretics, at the same time the diuretic effect amplifies and development of a hypopotassemia is prevented. At the same time at prolonged independent use of kaliysberegayushchy drugs it is necessary to consider a possibility of the by-effects connected with a hyperpotassemia, especially at patients with a renal failure.
The main representatives of this group of drugs - Spironolactonum and Triamterenum and also amiloride - differ on the action mechanism. Spironolactonum - the antagonist of Aldosteronum, and its therapeutic activity of subjects is higher, than, it is more than the level of Aldosteronum in organism liquids.
Triamterenum and amiloride are not antagonists of Aldosteronum, under the influence of these drugs the permeability of cellular covers of an epithelium of distal tubules for sodium ions decreases.
As for osmotic diuretics, they increase osmotic pressure in balls and tubules and water reabsorptions mainly in proximal tubules interfere.
The most active osmotic diuretics (a mannitol, etc.) apply to cause an artificial diuresis in acute poisonings (barbiturita, salicylates, etc.), an acute renal failure and also in an acute heart failure in patients with reduced renal filtration. As dehydrational means they are appointed in wet brain.
The applied earlier mercury diuretics Kmerkuzal, Promeranum in connection with high toxicity and implementation in practice of newer highly effective not mercury diuretics are excluded from the nomenclature of medicines.