Torasemide

Absorption

Torasemide is the diuretic with the highest oral bioavailability even in advanced stages of chronic kidney disease. This bioavailability tends to be higher than 80% regardless of the patient condition. The maximal serum concentration is reported to be of 1 hour and the absorption parameters are not affected by its use concomitantly with food.

Toxicity

The oral LD50 of torasemide in the rat is 5 g/kg. When overdose occurs, there is a marked diuresis with the danger of loss of fluid and electrolytes which has been seen to lead to somnolence, confusion, hypotension, hyponatremia, hypokalemia, hypochloremic alkalosis, hemoconcentration dehydration and circulatory collapse. This effects can include some gastrointestinal disturbances.
There is no increase in tumor incidence with torasemide and it is proven to not be mutagenic, not fetotoxic or teratogenic.

Description

Torasemide is a novel loop diuretic launched in 1993 after a 12-year gap from the last diuretic introduction. It is indicated for the treatment of hypertension and edema associated with chronic congestive heart failure, renal disease and hepatic cirrhosis. Torasemide exerts its major diuretic activity on the thick ascending limb of the Henle's loop to promote rapid and marked excretion of water, Na⁺, Cl^-, and to a lesser extent,K⁺ and Ca²⁺. Compared with other loop diuretics such as furosemide, torasemide has a stronger antihypertensive action, a higher bioavailability, a longer duration of action that is independent of the renal function, and has no side effects such as paradoxical antidiuresis. The mechanism of its vasodilating effect has been suggested to result from, at least in part, the competitive antagonism of the thromboxane A2 receptor.

Chemical properties

Crystalline Solid

Originator

Hafslund Nycomed Germany; Italy (Norway)

The Uses of Torasemide

Used as a diuretic

The Uses of Torasemide

Torasemide is a loop diuretic. Diuretics have been abused as performance-enhancing drugs and masking agents in doping in sports. Use of torsemide is effective for the treatment of edema associated with chronic renal failure. The pharmacology of torasemide is similar to that of frusemide,though torasemide has a longer duration of action with a plasma half-life of approximately 3.5 hours. It also causes a less marked loss of potassiumand calcium.

Background

Torasemide is a high-ceiling loop diuretic. Structurally, it is a pyridine-sulfonylurea used as an antihypertensive agent. Torasemide was first approved for clinical use by the FDA in 1993.

Indications

Torasemide is indicated for the treatment of edema associated with congestive heart failure, renal or hepatic diseases. From this condition, it has been observed that torasemide is very effective in cases of kidney failure.
As well, torasemide is approved to be used as an antihypertensive agent either alone or in combination with other antihypertensives.

What are the applications of Application

Torsemide is an inhibitor of NKCC

Definition

ChEBI: Torasemide is an N-sulfonylurea obtained by formal condensation of [(3-methylphenyl)amino]pyridine-3-sulfonic acid with the free amino group of N-isopropylurea. It is a potent loop diuretic used for the treatment of hypertension and edema in patients with congestive heart failure. It has a role as a loop diuretic and an antihypertensive agent. It is a N-sulfonylurea, an aminopyridine and a secondary amino compound. It is functionally related to a 4-aminopyridine.

Manufacturing Process

In a 100 ml three-necked flask equipped with magnetic stirrer, condenser, thermometer and dropping funnel 3-sulfonylchloride-4-chloropyridine (10 g, 1 eq., 46.7 mmoles) was suspended in t-butyl-methyl ether (MTBE) (30 ml) at room temperature. Ammonium hydroxide, 25% solution (13.5 ml, 2.13 eq.) was dropped into the suspension in a rate such that the temperature is allowed to increase to 22°-26°C, this temperature was maintained until all the ammonium hydroxide was added. The suspension was then to cooled to room temperature and was stirred for 1 h. The pH of the suspension was adjusted to 80.1 by the addition of a few drops of ammonium hydroxide, 25% solution. The suspension was filtered and washed with water (2 times 10 ml) and the wet product (8 g) dried at 40°C, under the 1 mm Hg vacuum. 3-Sulfonamide- 4-chloropyridine was isolated in 74.4% yield, 6.7 g.
A mixture of 0.01 moles of 3-sulfonamido-4-chloropyridine, 0.02 mole of 3- methylbenzylamine and 50 ml of dry ethanol was heated to reflux temperature for 9 h. After distillation of the ethanol the residue was taken up in an excess of diluted NaOH and the excess of amine was extracted by means of ether.
The aqueous solution was then decolourized with charcoal and filtered, and the filtrate was neutralized with acetic acid. The precipitated product was separated and purified by crystallization from a mixture of water and acetone.The 3-sulfonamido-4-(3-methylbenzyl)amino-pyridine crystallized in the form of beige coloured cristals having a melting point of 184°-186°C. 0.01 mole of 3-sulfonamido-4-(3-methylbenzyl)amino-pyridine was reacted with 0.015 mole of isopropylisocyanate in the presence of 0.02 mole of triethylamine and of 20 ml of dichloromethane, at room temperature for 20 h. After evaporation under vacuum, the residue was taken up in an excess of diluted Na2CO3, filtered off and acidified by means of acetic acid. After precipitation of the product it was filtered and washed several times with ice cold water. The 3-isopropylcarbamoylsulfonamido-4-(3-methylbenzyl)amino_x0002_pyridine (Torsemide) showing as a white powder, has a melting point of 147°- 149°C.

brand name

Torasemide is INN and BAN;Unat;Toradiur.

Therapeutic Function

Diuretic

Biochem/physiol Actions

Torsemide is a loop diuretic of the pyridine-sulfonylurea class with antialdosteronergic properties and inhibitor of the Na+/K+/2Cl- carrier system.

Pharmacokinetics

It is widely known that administration of torasemide can attenuate renal injury and reduce the severity of acute renal failure. This effect is obtained by increasing urine output and hence, facilitating fluid, acid-base and potassium control. This effect is obtained by the increase in the excretion of urinary sodium and chloride.
Several reports have indicated that torasemide presents a long-lasting diuresis and less potassium excretion which can be explained by the effect that torasemide has on the renin-angiotensin-aldosterone system. This effect is very similar to the effect observed with the administration of combination therapy with furosemide and spironolactone and it is characterized by a decrease in plasma brain natriuretic peptide and improved measurements of left ventricular function.
Above the aforementioned effect, torasemide presents a dual effect .in which the inhibition of aldosterone which donates torasemide with a potassium-sparing action.
Torasemide has been shown to reduce extracellular fluid volume and blood pressure in hypertensive patients suffering from chronic kidney disease. As well, some reports have indicated that torasemide can reduce myocardial fibrosis by reducing the collagen accumulation. This effect is suggested to be related to the decrease in aldosterone which in order has been shown to reduce the production of the enzyme procollagen type I carboxy-terminal proteinase which is known to be overexpressed in heart failure patients.

Clinical Use

Loop diuretic:
Hypertension
Oedema

Drug interactions

Potentially hazardous interactions with other drugs
Analgesics: increased risk of nephrotoxicity with NSAIDs; antagonism of diuretic effect with NSAIDs.
Anti-arrhythmics: risk of cardiac toxicity with anti-arrhythmics if hypokalaemia occurs; effects of lidocaine and mexiletine antagonised.
Antibacterials: increased risk of ototoxicity with aminoglycosides, polymyxins and vancomycin; avoid concomitant use with lymecycline.
Antidepressants: increased risk of hypokalaemia with reboxetine; enhanced hypotensive effect with MAOIs; increased risk of postural hypotension with tricyclics.
Antiepileptics: increased risk of hyponatraemia with carbamazepine.
Antifungals: increased risk of hypokalaemia with amphotericin.
Antihypertensives: enhanced hypotensive effect; increased risk of first dose hypotensive effect with alpha-blockers; increased risk of ventricular arrhythmias with sotalol if hypokalaemia occurs.
Antipsychotics: increased risk of ventricular arrhythmias with amisulpride or pimozide (avoid with pimozide) if hypokalaemia occurs; enhanced hypotensive effect with phenothiazines.
Atomoxetine: hypokalaemia increases risk of ventricular arrhythmias.
Cardiac glycosides: increased toxicity if hypokalaemia occurs.
Cytotoxics: increased risk of ventricular arrhythmias due to hypokalaemia with arsenic trioxide; increased risk of nephrotoxicity and ototoxicity with platinum compounds.
Lithium: risk of toxicity.

Metabolism

Torasemide is extensively metabolized in the liver and only 20% of the dose remains unchanged and it is recovered in the urine. Metabolized via the hepatic CYP2C8 and CYP2C9 mainly by reactions of hydroxylation, oxidation and reduction to 5 metabolites. The major metabolite, M5, is pharmacologically inactive. There are 2 minor metabolites, M1, possessing one-tenth the activity of torasemide, and M3, equal in activity to torasemide. Overall, torasemide appears to account for 80% of the total diuretic activity, while metabolites M1 and M3 account for 9% and 11%, respectively.

Metabolism

Torasemide is metabolised by the cytochrome P450 isoenzyme CYP2C9 to three inactive metabolites, M1, M3 and M5 by stepwise oxidation, hydroxylation or ring hydroxylation. The inactive metabolites are excreted in the urine.