Diuretic effect and disposition of furosemide in cystic fibrosis

Diuretics in pediatrics : current knowledge and future prospects

This review summarizes current knowledge on the pharmacology, pharmacokinetics, pharmacodynamics, and clinical application of the most commonly used diuretics in children. Diuretics are frequently prescribed drugs in children. Their main indication is to reduce fluid overload in acute and chronic disease states such as congestive heart failure and renal failure. As with most drugs used in children, optimal dosing schedules are largely unknown and empirical. This is undesirable as it can potentially result in either under- or over-treatment with the possibility of unwanted effects. The pharmacokinetics of diuretics vary in the different pediatric age groups as well as in different disease states. To exert their action, all diuretics, except spironolactone, have to reach the tubular lumen by glomerular filtration and/or proximal tubular secretion. Therefore, renal maturation and function influence drug delivery and consequently pharmacodynamics. Currently advised doses for diuretics are largely based on adult pharmacokinetic and pharmacodynamic studies. Therefore, additional pharmacokinetic and pharmacodynamic studies for the different pediatric age groups are necessary to develop dosing regimens based on pharmacokinetic and pharmacodynamic models for all routes of administration.

Furosemide: progress in understanding its diuretic, anti-inflammatory, and bronchodilating mechanism of action, and use in the treatment of respiratory tract diseases

Accumulated experimental and clinical data suggest that adrenocorticosteroids and/or endogenous ouabain-like substances may play an important role in the mechanism of furosemide diuretic action. It was reported that the drug is highly bound in the adrenals, lungs, kidney, spleen, and liver. In patients with liver cirrhosis, furosemide exerted a markedly decreased natriuretic effect compared with normal subjects, and the plasma levels of circulating endothelin and atrial natriuretic factor (ANF) were significantly elevated. In neonates, after administration of furosemide, the urinary excretion of endothelin-1 and aldosterone increased markedly, and it is known that endothelin may release ANF and aldosterone in a dose-dependent manner. Furosemide was used to stimulate zona glomerulosa, whereas ANF decreased the production of steroids in zona glomerulosa and fasciculata cell culture owing to stimulation by various factors. Because the concomitant use of ANF and furosemide appeared to be diuretically effective in newborns after cardiac surgery, one may suggest that furosemide competes with ANF for its effects on the adrenals. Furosemide administered by inhalation exerted a protective effect on allergic and perennial nonallergic rhinitis and was effective in preventing the postsurgical recurrence of nasal polyposis. The drug can also be used as an antiasthmatic agent. In preterm ventilator-dependent infants with chronic lung disease, aerosolized furosemide improved pulmonary function with no marked effect on diuresis. In adults and children with asthma, furosemide exerted a protective effect against bronchoconstriction induced by several indirect stimuli similar to that of disodium cromoglycate or nedocromil. Aerosolized furosemide had a preventive effect also on bronchoconstriction induced by inhaled lysine acetylsalicylate in patients with aspirin-sensitive asthma. In high-dose beclomethasone-dependent asthma, inhaled lysine acetylsalicylate and furosemide exerted a mutually potentiating antiasthmatic activity, allowing considerable sparing of the inhaled steroid. It is proposed that this effect may be explained by the corticosteroid-sparing action of lysine released from the lysine acetylsalicylate molecule because similar beneficial effects were also obtained after the concomitant use of epsilon-aminocaproic acid (whose chemical structure is almost the same as that of lysine) and prednisone. Furosemide exhibited an anti-inflammatory effect through inhibition of production and release of cytokines interleukin (IL)-6, IL-8, and tumor necrosis factor-alpha from peripheral mononuclear cells, which may have a beneficial effect on local inflamed tissue imbalance in the ratio of different cytokines, thus improving the sensitivity of target cells to endogenous glucocorticosteroids.

Clinical pharmacology of furosemide in children: a supplement

Furosemide is one of the most effective and least toxic diuretics used in pediatric practice. Experimental and clinical data suggest that adrenocorticosteroids and/or endogenous ouabain-like substances may play an important role in its diuretic effect. Also, the drug appears to have anti-inflammatory properties. In children with different diseases who received orally or intravenously 1 to 2 mg/kg doses of furosemide, a statistically significant positive linear relationship was found between the drug urinary excretion rate and the urine flow rate, but log dose-response curves to the drug were found to vary depending on the disease and the route of the drug administration. No sigmoid-shaped log dose-response curve (ie, one approaching a zero response at very low furosemide urinary excretion rates and a maximum response at very high excretion rates) was attained, which may suggest that the capacity of the kidney tubules to respond diuretically to the aforementioned doses of furosemide was not exceeded in these patients. However, in infants with different diseases and reasonably normal renal function who required administration of this diuretic, a very steep log dose-response curve to a 1 mg/kg intravenous dose of furosemide was found, which may suggest that higher doses may not result in a significant increase in diuretic response. The lowest mean furosemide urinary excretion rate and its concentration in urine associated with a significant diuresis were found to be 0.58 +/- 0.33 microg/kg/min and 24.2 +/- 10.5 microg/ml, respectively. Also, a significant correlation was found between the amount (in milligrams) of furosemide excreted in the urine during the first 6 hours after administration and the urine volume collected during that time. Patients with cystic fibrosis appeared to have a markedly more pronounced diuretic response to the average oral dose of 0.835 +/- 0.18 mg/kg than that reported in control children given 2 mg/kg. In children with acute renal failure caused by acute gastroenterocolitis or glomerulonephritis, a broad relationship was observed between a single intravenous dose and diuretic response after administration of furosemide (1.2 to 30.8 mg/kg). It was suggested that the total daily dose of the drug should not exceed 100 mg in these patients. Furosemide was found to be effective in management of bronchoconstriction accompanying chronic lung disease and narrowing of the upper respiratory airways; in hydrocephalus in infancy to avoid cerebrospinal fluid shunts; in some diagnostic procedures, such as an assessment of fetal and neonatal hydronephrosis; and in evaluation of different types of renal tubular acidosis. Among side effects accompanying clinical use of this drug were cholelithiasis in premature infants receiving total parenteral nutrition concomitantly with the diuretic; secondary hyperparathyroidism and bone disease in infants obtaining long-term furosemide treatment; and drug-induced fever.