Development of acute tolerance to bumetanide: bolus injection studies

Diuretic therapy in congestive heart failure

In heart failure, fluid overload is a major pathological mechanism leading to vascular congestion, pulmonary congestion and elevated jugular venous pressures. Diuretics play a significant role in the management of patients with congestive heart failure. It is used to relieve the congestive symptoms of heart failure. However, the appropriate use of diuretics remains challenging due to various complications like electrolyte abnormalities, worsening renal function and diuretic resistance. This has prompted towards the search of safer and effective alternatives. This review evaluates the use of diuretics in congestive heart failure and discusses the complications of different types of diuretics, which is essential for successful management of congestion in patients with heart failure and hence to optimise the outcome for the patients.

Continuous infusion versus bolus injection of loop diuretics in congestive heart failure

BACKGROUND

Loop diuretics, when given as intermittent bolus injections in acutely decompensated heart failure, may cause fluctuations in intravascular volume, increased toxicity and development of tolerance. Continuous infusion has been proposed to avoid these complications and result in greater diuresis, hopefully leading to faster symptom resolution, decrease in morbidity and possibly, mortality.

OBJECTIVES

To compare the effects and adverse effects of continuous intravenous infusion of loop diuretics with those of bolus intravenous administration among patients with congestive heart failure Class III-IV.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 2, 2003), MEDLINE (1966 to 2003), EMBASE (1980 to 2003) and the HERDIN database. We also contacted pharmaceutical companies .

SELECTION CRITERIA

Randomized controlled trials comparing the efficacy of continuous intravenous infusion versus bolus intravenous administration of loop diuretics in congestive heart failure were included

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed study eligibility, methodological quality and did data extraction. Included studies were assessed for validity. Authors were contacted when feasible. Adverse effects information was collected from the trials.

MAIN RESULTS

Eight trials involving 254 patients were included. In seven studies which reported on urine output, the output (as measured in cc/24 hours) was noted to be greater in patients given continuous infusion with a weighted mean difference (WMD) of 271 cc/24 hour (95%CI 93.1 to 449; p<0.01). Electrolyte disturbances (hypokalemia, hypomagnesemia) were not significantly different in the two treatment groups with a relative risk (RR) of 1.47 (95%CI 0.52 to 4.15; p=0.5). Less adverse effects (tinnitus and hearing loss) were noted when continuous infusion was given, RR 0.06 (95%CI 0.01 to 0.44; p=0.005). Based on a single study, the duration of hospital stay was significantly shortened by 3.1days with continuous infusion WMD -3.1 (95%CI -4.06 to -2.20; p<0.0001) while cardiac mortality was significantly different in the two treatment groups, RR 0.47 (95% CI 0.33 to 0.69; p<0.0001). Based on two studies, all cause mortality was significantly different in the two treatment groups, RR 0.52 (95%CI 0.38 to 0.71; p<0.0001).

AUTHORS' CONCLUSIONS

Currently available data are insufficient to confidently assess the merits of the two methods of giving intravenous diuretics. Based on small and relatively heterogenous studies, this review showed greater diuresis and a better safety profile when loop diuretics were given as continuous infusion. The existing data still does not allow definitive recommendations for clinical practice and larger studies should be done to more adequately settle this issue.

Continuous infusion versus bolus injection of loop diuretics in congestive heart failure

BACKGROUND

Loop diuretics, when given as intermittent bolus injections in acutely decompensated heart failure, may cause fluctuations in intravascular volume, increased toxicity and development of tolerance. Continuous infusion has been proposed to avoid these complications and result in greater diuresis, hopefully leading to faster symptom resolution, decrease in morbidity and possibly, mortality.

OBJECTIVES

To compare the effects and adverse effects of continuous intravenous infusion of loop diuretics with those of bolus intravenous administration among patients with congestive heart failure Class III-IV.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 2, 2003), MEDLINE (1966 to 2003), EMBASE (1980 to 2003) and the HERDIN database. We also contacted pharmaceutical companies.

SELECTION CRITERIA

Randomized controlled trials comparing the efficacy of continuous intravenous infusion versus bolus intravenous administration of loop diuretics in congestive heart failure were included

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed study eligibility, methodological quality and did data extraction. Included studies were assessed for validity. Authors were contacted when feasible. Adverse effects information was collected from the trials.

MAIN RESULTS

Eight trials involving 254 patients were included. In seven studies which reported on urine output, the output (as measured in cc/24 hours) was noted to be greater in patients given continuous infusion with a weighted mean difference (WMD) of 271 cc/24 hour (95%CI 93.1 to 449; p<0.01). Electrolyte disturbances (hypokalemia, hypomagnesemia) were not significantly different in the two treatment groups with a relative risk (RR) of 1.47 (95%CI 0.52 to 4.15; p=0.5). Less adverse effects (tinnitus and hearing loss) were noted when continuous infusion was given, RR 0.06 (95%CI 0.01 to 0.44; p=0.005). Based on a single study, the duration of hospital stay was significantly shortened by 3.1days with continuous infusion WMD -3.1 (95%CI -4.06 to -2.20; p<0.0001) while cardiac mortality was not significantly different in the two treatment groups, RR 0.47 (95% CI 0.33 to 0.69; p<0.0001). Based on two studies, all cause mortality was not significantly different in the two treatment groups, RR 0.52 (95%CI 0.38 to 0.71; p<0.0001).

REVIEWER'S CONCLUSIONS

Currently available data are insufficient to confidently assess the merits of the two methods of giving intravenous diuretics. Based on small and relatively heterogenous studies, this review showed greater diuresis and a better safety profile when loop diuretics were given as continuous infusion. The existing data still does not allow definitive recommendations for clinical practice and larger studies should be done to more adequately settle this issue.

A study of the pharmacodynamic differences between immediate and extended release bumetanide formulations

Optimized bumetanide extended (ER) and immediate release (IR) formulations were developed using fluid bed layering and coating techniques. We postulated that the ER bumetanide formulation would have more effective and sustained diuretic and saluretic effects than IR. The diuretic/saluretic effects of both formulations were measured in rabbits (n=8) for two days after dosing with 1mg/kg bumetanide. During the first day, both formulations produced 2-3 times more urine volume and sodium excretion than baseline. In the first 24h, despite less bumetanide excretion from the ER formulation (101+/-13.9microg/kg compared to 146+/-14.6microg/kg for the IR formulation; P<0.04); the ER formulation produced diuresis and natriuresis that was equivalent to that of the IR formulation. In contrast, urine production in the IR formulation group fell below that of placebo controls on day 2. During the second day, the ER formulation was noted to produce persistent bumetanide excretion; the diuretic and natriuretic effects were not statistically significant from baseline control. We speculate that the decrease in response to bumetanide observed especially for the IR formulation during the second day may be due to the activation of compensatory counter-regulatory homeostatic mechanism(s). We conclude that the ER formulation had similar diuretic/saluretic effects but better drug excretion to urine production efficiencies than the IR formulation in the healthy rabbit model. The ER formulation, while providing comparable diuretic/saluretic effect to the IR formulation, offers the advantage of avoiding the initial, rapid and robust diuretic effect experienced with the IR formulations. Taken together, the data provide sufficient basis to warrant further investigation and refinement of our ER bumetanide formulation in humans.

Studies on the Metabolic Fate of M17055, a Novel Diuretic (5): Pharmacokinetics and Pharmacodynamics of Unchanged Drug in Rat and Dog After Intravenous Administration of M17055

The pharmacokinetics and pharamacodynamics of M17055, a novel diuretic were studied after a single intravenous administration to rats and dogs, the two species used in the pharmacological and toxicological studies. No gender dependent response to systemic exposure was observed at the high dose level in rats, in agreement with the determined LD(50). A gender difference in urinary excretion of M17055, however, was clearly observed in rats. The slower elimination and the lower total body clearance (CLtot) values of M17055 in dogs reflect the difference of the no-effect level (NOEL) between rats (0.1 mg/kg) and dogs (0.03 mg/kg) well. The diuretic response was well correlated with the urinary M17055 excretion rate by fitting to a sigmoid E(max) model in both rats and dogs. The derived ER(50) value of M17055 in dogs was approximately 10 times less than that reported for furosemide, suggesting that the intrinsic potency of M17055 is equal to or higher than those of other powerful loop diuretics. Although diuretic sensitivity was considered to be lower in dogs than in rats, the higher amount of M17055 reaching the dog kidney is likely to compensate for this. The diuretic response in female rats was predictable by using the pharmacodynamic parameters derived from male rats. These results show that the apparent high diuretic potency and the other pivotal observations for M17055 found in the pharmacological and toxicological studies can be rationalized by the pharmacokinetic and pharmacodynamic properties of the unchanged compound.

Effects of the rate and composition of fluid replacement on the pharmacokinetics and pharmacodynamics of intravenous bumetanide

The effects of differences in the rate and composition of intravenous (i.v.) fluid replacement for urine loss on the pharmacokinetics and pharmacodynamics of bumetanide were evaluated with rabbit as the animal model. Each rabbit received a 4-h constant i.v. infusion of bumetanide at 1 mg/kg with 0% replacement (treatment I, n = 8), 50% replacement (treatment II, n = 6), and 100% replacement (treatment III, n = 7) with lactated Ringer's solution, in addition, another group of rabbits received 100% replacement with 5% dextrose in water (D-5-W, treatment IV, n = 4). Some pharmacokinetic parameters, such as the apparent volume of distribution at steady-state, mean residence time, and terminal half-life, remained relatively unchanged in all four treatments. Renal clearance and urinary excretion rate of the drug in treatments I-III were essentially the same, but were considerably higher than those in treatment IV. In spite of the similarities in kinetic properties (approximately 40% difference between lowest and highest values), the diuretic and/or natriuretic effects of bumetanide were markedly different among the four treatments. For example, the mean 8-h urine output values were 189, 317, 2170, and 306 mL for treatments I-IV, respectively, the corresponding 8-h sodium excretion values were 9.19, 16.5, 88.8, and 15.7 mmol, and the chloride excretion values were 10.8, 33.7, 77.4, and 11.7 mmol. Except for treatment III, diuresis and/or natriuresis were time dependent, generally decreasing with time until reaching a low plateau during later hours of infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of water deprivation on the pharmacokinetics and pharmacodynamics of bumetanide in rats

The effects of temporary water deprivation for 48 h on the pharmacokinetics and pharmacodynamics of bumetanide were examined after intravenous (i.v.) administration of bumetanide, 8 mg kg-1 to control and water deprived rats (n = 7). The values of AUC, t1/2 and MRT increased 79.0, 417, and 633 per cent, respectively, and CL and CLNR decreased 44.0 and 41.2 per cent, respectively, in water deprived rats. They were all significantly different. The decreased CLNR in water deprived rats could be due to decreased nonrenal metabolism of bumetanide; it could be supported that the amounts of glucuronide conjugate of bumetanide (52.5 vs 12.9 micrograms), desbutylbumetanide (170 vs 113 micrograms) and its glucuronide conjugation (191 vs 125 micrograms), and sum of the three metabolites (414 vs 229 micrograms), which are expressed in terms of bumetanide excreted in 24 h urine, decreased significantly in water deprived rats. The 8-h urine outputs per 100 g body weight (4.32 vs 1.34 ml) also reduced significantly in water deprived rats, and it might be due to significantly reduced amounts of bumetanide excreted in 8 h urine (90.9 vs 25.7 micrograms) and/or reduced kidney function in water deprived rats. The kidney function based on CLIot (9.87 vs 2.14 ml min-1 kg-1) reduced significantly in water deprived rats. The 8-h urinary excretions of sodium (0.430 vs 0.0818 mmol), potassium (0.567 vs 0.270 mmol), and chloride (0.549 vs 0.0624 mmol) per 100 g body weight also reduced significantly in water deprived rats.

Abuse of drugs associated with eating disorders

Concomitant bulimia nervosa and drug abuse are common in women. Drugs used by this group include diuretics, emetics, laxatives, and diet pills, as well as alcohol, cigarettes, and illicit street drugs. This paper applies principles from behavioral pharmacology to the problem of drug use by women with bulimia nervosa. The prevalence of use, primary effects, toxicity, detection, tolerance, withdrawal, and effects on appetite and weight are discussed for drugs used by bulimic women to reduce appetite or weight or to induce purging (e.g., diuretics, emetics, laxatives, and diet aids). Alternatives in the diagnosis and treatment of drug use in women with eating disorders are discussed.

Analysis of the natriuretic action of a loop diuretic, piretanide, in man

1. The renal responses to a loop diuretic, piretanide, were investigated in a group of fourteen healthy volunteers. The effect of fluid replacement on the drug-response relationship was evaluated in the absence and in the presence of probenecid pretreatment following both oral and intravenous administration of piretanide. 2. Urinary excretion of piretanide was greater when volume losses were replaced than in the absence of volume replacement (i.v. dose: 3.32 +/- 0.15 vs 2.55 +/- 0.23 mg 6 h-1, P less than 0.01; oral dose: 2.57 +/- 0.09 vs 1.87 +/- 0.27 mg 6 h-1, P less than 0.01). With intravenous piretanide urinary excretion of sodium was likewise greater in the fluid replaced group (198 +/- 4 vs 141 +/- 10 mmol 6 h-1, P less than 0.01); these differences caused by fluid replacement did not however occur after oral dosing of piretanide (181 +/- 12 vs 167 +/- 14 mmol 6 h-1). 3. Probenecid pretreatment significantly decreased the renal excretion of piretanide in all subjects and consistently decreased the natriuretic response with the exception of intravenous piretanide challenge in subjects not undergoing fluid replacement. In this situation, despite probenecid causing a decrease in the amount of drug excreted (2.55 +/- 0.23 vs 1.63 +/- 0.15 mg 6 h-1, P less than 0.05) the sodium output was unaltered (141 +/- 10 vs 152 +/- 16 mmol 6 h-1, NS). 4. Complete replacement of the induced fluid losses resulted in the enhancement of the renal response, without affecting the shape of the diuretic response curve, of either the intravenous or orally administered piretanide.(ABSTRACT TRUNCATED AT 250 WORDS)

Development of acute tolerance to bumetanide: constant-rate infusion studies

Bumetanide was administered intravenously to four mongrel dogs as a bolus of 8.7 micrograms/kg, immediately followed by a constant-rate infusion of 0.35 microgram/min/kg at 0.036 ml/min. Treatment A consisted of a 90-min equilibration period and first hour (Phase I) of study in which animals were maintained under euvolemic conditions. During the subsequent 3 hr of Treatment A (Phase II), animals were maintained under hydropenic conditions. These experiments were then repeated 1 week later (Treatment B) with the temporal aspects of hydration reversed (Phase III, hydropenia; Phase IV, euvolemia). Serial plasma and urine samples were assayed for bumetanide by high-performance liquid chromatography (HPLC) and for sodium by flame photometry. The bumetanide excretion rate was not significantly different during the 4 hr of Treatment A, although minor differences were observed between Phase III and Phase IV of Treatment B. The sodium excretion rate showed significant differences between euvolemic and hydropenic conditions of both treatments. A two- to threefold difference in the sodium excretion rate persisted even when slight differences (less than 20%) in bumetanide excretion rates were taken into account. These results demonstrate that an acute tolerance does develop to constant-rate infusions of bumetanide when inadequate fluid and electrolyte replacement occurs and that this tolerance can be reversed by rehydration.