Urinary excretion profile of torasemide and its diuretic action in dogs

Pharmacokinetic and pharmacodynamic properties of orally administered torasemide in healthy cats

BACKGROUND

In people and dogs, torasemide has higher bioavailability, longer half-life, and longer duration of action than equivalent doses of furosemide but data regarding pharmacological properties of torasemide in cats are limited.

OBJECTIVE

To assess pharmacokinetic and pharmacodynamic parameters of torasemide in healthy cats, and to investigate the effects of a single administration of torasemide on indicators of diuresis, plasma creatinine concentration, blood pressure, electrolyte concentrations and markers of the renin-angiotensin-aldosterone system (RAAS).

ANIMALS

Six clinically healthy adult European shorthair cats.

METHODS

Randomized 4-period crossover design with 3 groups and 4 treatments. Pharmacokinetic parameters were obtained using a noncompartmental analysis, and the clinically effective dose was assessed using a Hill model.

RESULTS

Mean absolute bioavailability was estimated at 88.1%. Mean total body clearance was 3.64 mL/h/kg and mean terminal half-life was 12.9 hours. Urine output significantly increased after torasemide administration (P < .001). The urine sodium : potassium ratio (uNa : uK) paralleled and was statistically correlated to urine output (P < .001). Administration of a single torasemide dose led to a significant dose-dependent increase in urine aldosterone : creatinine ratio (uAldo : C; P < .001) and a transient decrease in plasma potassium concentration (P < .001) but did not affect blood pressure or plasma creatinine concentration.

CONCLUSIONS AND CLINICAL IMPORTANCE

A single torasemide dose leads to a significant increase in diuresis and renin-angiotensin-aldosterone system (RAAS) activation in healthy cats, with high absolute bioavailability, and without clinically relevant adverse effects. Pharmacokinetic parameters indicate that once daily dosing of 0.27 mg/kg may be appropriate in a clinical setting.

Safety of torasemide in healthy adult dogs administered daily for 26 weeks

Thirty‐two (16 males and 16 females) healthy young beagles were randomly divided into four groups of eight. The control group remained untreated. Torasemide (ISEMID^®, Ceva Santé Animale) was orally administered, once daily, at 0.5 mg/kg from Days 1–5 then 0.25 mg/kg to Day 182, and at three times and five times this dosing regimen in two additional groups. Treated animals (predominantly at the higher dose levels) showed dryness of the oral mucosa, evidence of diuresis, decreased diet consumption, decreased bodyweight gain over the first 3 weeks, increased water consumption, increases in erythrocytes count, haemoglobin, calcium and magnesium, decrease in chloride, phosphorus, potassium and sodium, increases in urine pH, decreases in urine specific gravity and increases in serum aldosterone concentrations. Plasma concentrations of torasemide increased in a dose‐dependent manner and showed no evidence of accumulation. There were also changes to electrocardiogram patterns and the macroscopic and microscopic appearance of the kidney and adrenal glands, but these changes were almost exclusively confined to the over‐dosed groups. In conclusion, torasemide was found to be safe when administered to dogs at 0.25 mg/kg once daily for 26 weeks, and any changes were consistent with its known diuretic effects.

Efficacy of oral torasemide in dogs with degenerative mitral valve disease and new onset congestive heart failure: The CARPODIEM study

Background

Torasemide is a potent loop diuretic with potential to treat congestive heart failure (CHF) in dogs.

Objective

Evaluate the efficacy and safety of torasemide compared to furosemide in dogs with first occurrence of CHF caused by degenerative mitral valve disease (DMVD).

Animals

Three hundred and nineteen dogs with new onset CHF attributable to DMVD.

Methods

Double‐blinded randomized noninferiority study of PO torasemide vs furosemide in addition to standard CHF treatment. The primary efficacy criterion was decreased pulmonary edema and cough and no worsening of dyspnea or exercise tolerance at day 14. Secondary endpoints included clinical response at day 84 and time to death, euthanasia, or premature study withdrawal for cardiac reasons.

Results

Torasemide q24h (n = 161) was noninferior to furosemide q12h (n = 158); percentage of dogs meeting primary efficacy criterion at day 14 was similar between groups (torasemide, 74.4% [95% confidence interval (CI), 66.8%‐81.0%] vs. furosemide, 73.5% [95% CI, 65.7%‐80.4%]; risk ratio [RR], 1.01; 95% CI, 0.89‐1.15; P = .87). Efficacy at day 84 showed similar results (RR, 1.05; 95% CI, 0.88‐1.25; P = .6). Dogs receiving torasemide had a longer time to endpoint and were less than half as likely to experience death, euthanasia, or premature study withdrawal (hazard ratio, 0.36; 95% CI, 0.19‐0.65; P = .001) than dogs receiving furosemide at any time during the study.

Conclusion and Clinical importance

Torasemide was noninferior to furosemide as first line PO treatment for new onset CHF caused by DMVD. Torasemide significantly decreased risk of cardiac‐related death or premature study withdrawal for cardiac reasons compared to furosemide.

Role of electrolyte concentrations and renin-angiotensin-aldosterone activation in the staging of canine heart disease

Background

Refractory congestive heart failure (CHF) and associated diuretic resistance are not well defined.

Objectives

To characterize renal function, electrolyte concentrations, indices of diuretic efficacy, and renin‐angiotensin‐aldosterone system (RAAS) activation in dogs with naturally occurring heart disease (HD) in American College of Veterinary Internal Medicine stages B1, B2, C, and D and to determine their usefulness in defining HD stages.

Animals

Group 1:149 dogs with HD stages B1, B2, C, and D. Group 2:22 dogs with HD stages C and D.

Methods

Group 1: Renal parameters, serum and urine electrolyte and diuretic concentrations, and urine aldosterone concentrations were measured. Medication dosages and measured variables were compared among stages. Correlation of furosemide dosages to serum concentrations was explored. Group 2: Angiotensin‐converting enzyme activity and RAAS components were measured and compared among CHF stages.

Results

Serum chloride concentration was the best differentiator of HD stage. Furosemide PO dosages (≤6 mg/kg/day) were weakly correlated with serum furosemide concentrations, whereas higher dosages were not significantly correlated. Angiotensin‐converting enzyme inhibitor dosage and RAAS inhibition were greater in stage D, compared to stage C dogs.

Conclusions and Clinical Importance

Hypochloremia is a useful marker for stage D HD in dogs. Poor furosemide dosage correlation to serum concentration may indicate variable and poor absorption, especially at higher dosages, advanced disease, or both. A small number of stage D dogs met proposed criteria for diuretic resistance. Greater RAAS inhibition in stage D versus stage C indicates effectiveness of RAAS‐suppressive treatments in this group of dogs with refractory CHF.

Comparison between the effects of torsemide and furosemide on the renin-angiotensin-aldosterone system of normal dogs

INTRODUCTION/OBJECTIVES

We hypothesized that torsemide and furosemide, at approximately equipotent dosages (similar diuresis), would have comparable effects on the circulating renin-angiotensin-aldosterone system.

ANIMALS, MATERIALS AND METHODS

Six, healthy, middle-aged, male Beagles were randomized to receive torsemide (0.1 mg/kg PO q 12 h), furosemide (2.0 mg/kg PO q 12 h), or placebo for 10 days during three separate periods, separated by a 10-day washout period, in a crossover design. Blood was collected on days 1, 5, and 9 and 24-h urine collection ended on days 2, 6, and 10. After repeated measures analysis and Bonferonni correction, variables with an adjusted p<0.05 were investigated further, using Tukey's method.

RESULTS

Twenty-four-hour urine production differed significantly between the diuretics only on day 10, with torsemide causing a 38% greater diuresis than furosemide. There was, however, no significant difference in average 3-day diuresis. There were no significant differences between diuretics in the 24-h urinary excretion of sodium, chloride, or potassium, though furosemide caused less kaliuresis than torsemide. Serum renin, angiotensin II, and aldosterone and the urine aldosterone-to-creatinine ratio were significantly increased in the diuretic groups, as compared to placebo on days 5/6 and 9/10. There were no significant differences in these values between diuretics. Creatinine and blood urea nitrogen concentrations rose comparably in the diuretic groups, remaining within reference intervals in all dogs.

CONCLUSIONS

At approximately equipotent dosages (20:1), torsemide and furosemide produced comparable renin-angiotensin-aldosterone system activation. Torsemide's similar potassium excretion profile to furosemide decreases support for a hypothesized mineralocorticoid-receptor blocking capability.

Short-Term Efficacy and Safety of Torasemide and Furosemide in 366 Dogs with Degenerative Mitral Valve Disease: The TEST Study

BACKGROUND

Furosemide is the only loop diuretic recommended by the ACVIM consensus guidelines for treatment of congestive heart failure (CHF) in dogs related to degenerative mitral valve disease (DMVD). Torasemide is another potent loop diuretic with a longer half-life and a higher bioavailability.

OBJECTIVES

(1) To demonstrate that torasemide given once a day (q24h) is noninferior to furosemide given twice a day (q12h) for treating dogs with CHF; (2) and to compare the effect of the 2 drugs on the time to reach a composite cardiac endpoint "spontaneous cardiac death, euthanasia due to heart failure or CHF class worsening."

ANIMALS

A total of 366 dogs with CHF attributable to DMVD.

METHODS

Analysis of 2 prospective randomized single-blinded reference-controlled trials was performed. Dogs orally received either torasemide q24h (n = 180) or furosemide q12h (n = 186) in addition to standard CHF therapy over 3 months. The primary efficacy criterion was the percentage of dogs with treatment success assessed in each study. The time to reach the composite cardiac endpoint was used as secondary criterion in the overall population.

RESULTS

Torasemide was noninferior to furosemide (Ptorasemide  - Pfurosemide  = +7%; 95% CI [-8%; +22%] and Ptorasemide  - Pfurosemide  = +1%; 95% CI [-12%; +14%], respectively, in Study 1 and Study 2). Torasemide (median dose = 0.24 mg/kg/d q24h; range = 0.10-0.69 mg/kg/d) was associated with a 2-fold reduction in the risk of reaching the composite cardiac endpoint (adjusted HR = 0.47; 95% CI = 0.27-0.82; P = 0.0077) as compared with furosemide (median dose = 1.39 mg/kg q12h; range = 0.70-6.30 mg/kg q12h).

CONCLUSIONS AND CLINICAL IMPORTANCE

Torasemide q24h is an effective oral diuretic in dogs with CHF.

Long-term Stability of a Compounded Suspension of Torsemide (5 mg/mL) for Oral Administration

Background

Torsemide use for congestive heart failure (CHF) has been reported, but prescription frequency is unknown. Commercially available tablet sizes in North America limit dosing precision, indicating a need to evaluate its strength and stability in suspension.

Objectives

To determine the frequency of torsemide prescriptions and to determine a beyond use date (BUD) of a compounded suspension of torsemide for oral administration stored under 2 temperature conditions for 90 days.

Animals

No animals used.

Methods

Pharmacy records were retrospectively reviewed for torsemide and furosemide prescriptions from 2008 to 2015 at 2 veterinary referral centers. After preliminary strength testing, compounded torsemide suspension (5 mg/mL) for oral administration was prepared using torsemide tablets suspended in OraPlus:OraSweet 1:1, buffered to a pH of 8.3 and stored at refrigeration (2–8°C) and room temperature (20–25°C) in 2 oz amber plastic bottles. Samples were analyzed by reverse phase high‐performance liquid chromatography (RP‐HPLC) on days 0, 14, 30, 60, and 90.

Results

Prescriptions for torsemide increased from 2008 to 2015. Analysis of the torsemide 5 mg/mL suspension for oral administration at each time point met United States Pharmacopeia (USP) requirements for torsemide content of 90–110% of label claim. The average strength at 90 days decreased to 92 ± 3% at 2–8°C and 95 ± 2% at 20–25°C. Stability testing did not detect unknown impurities.

Conclusions

Increasing torsemide use warrants availability of a validated and stable compounded formulation. Our results support the assignment of a 90‐day BUD for torsemide 5 mg/mL suspension for oral administration compounded in OraPlus:Sweet 1:1 buffered to a pH of 8.3.

Effect of torsemide and furosemide on clinical, laboratory, radiographic and quality of life variables in dogs with heart failure secondary to mitral valve disease

OBJECTIVES

Diuretic therapy reduces preload and relieves congestion secondary to cardiac dysfunction. Torsemide (torasemide) is a loop diuretic with longer duration of action, decreased susceptibility to diuretic resistance, and adjunctive aldosterone antagonist properties compared with furosemide. We hypothesized that torsemide would be well tolerated and no less effective than furosemide at diuresis, control of clinical signs, and maintenance of quality of life (QOL) in dogs with congestive heart failure (CHF).

ANIMALS, MATERIALS AND METHODS

Seven client-owned dogs with stable CHF receiving twice daily oral furosemide and adjunctive medications. Utilizing a double-blinded, randomized, crossover design, dogs were administered either oral furosemide at their current dose or an equivalent oral dose of torsemide (1/10 of the daily furosemide dose divided into twice daily dosing) on day 0. Crossover occurred at day 7 and the study ended on day 14. Clinical, laboratory, radiographic, and QOL variables were evaluated on days 0, 7 and 14.

RESULTS

No dogs developed recurrent CHF during the study. Mean furosemide dose on day 0 was 5.13 mg/kg/day (range 2.8-9.6). Following torsemide treatment, creatinine (P = 0.020), urea nitrogen (P = 0.013), phosphorus (P = 0.032), albumin (P = 0.019), carbon dioxide (P = 0.015) and anion gap (P = 0.005) were significantly increased, and urine specific gravity (P = 0.004) and chloride (P = 0.021) were significantly decreased compared with furosemide dosing. No differences in QOL were found.

CONCLUSIONS

Results indicate that torsemide is equivalent to furosemide at controlling clinical signs of CHF in dogs and is likely to achieve greater diuresis vs. furosemide. Larger clinical trials evaluating torsemide as a first or second-line loop diuretic for congestive heart failure in dogs are warranted.

The Effects of the Loop Diuretics Furosemide and Torasemide on Diuresis in Dogs and Cats

Torasemide is a new loop diuretic that combines the effects of furosemide and spironolactone. There are no reports on the effects of torasemide in cats and dogs. This study compared the diuretic effects of furosemide and torasemide in cats and dogs. Cats with pressure overload cardiac hypertrophy were given oral placebo, torasemide 0.3 mg/kg, or furosemide 1 mg/kg or 3 mg/kg. Control and mitral regurgitation dogs were given oral placebo, torasemide 0.2 mg/kg, and furosemide 2 mg/kg for 7 days. Urine samples were obtained at baseline and 1, 2, 3, 4, 5, 6, 8, 12, and 24 hr after each drug dose. Urine volume and urine Na(+) and K(+) were measured. Both furosemide and torasemide increased urine volume 1 hr after administration. Furosemide caused a dose-dependent increase in urine volume that peaked at 2-3 hr in cats and dogs. The diuretic effect of furosemide disappeared 6 hr after administration, while that of torasemide peaked 2-4 hr after administration and persisted for 12 hr in cats and dogs. In MR dogs, torasemide for 7 days significantly decreased urine potassium excretion. Plasma aldosterone increased with torasemide, whereas there was no change with furosemide. In conclusion, about 1/10 concentration of torasemide was as potent as furosemide and had a longer diuretic effect in cats and dogs. These data suggest that torasemide is useful for treating congestive heart failure or edema in cats and dogs.