Magnesium excretion, urinary

Massey, L. K., Wise, K. J., The effect of dietary caffeine on urinary excretion of calcium, magnesium, sodium and potassium in healthy young females, Nutrition Research, 4, 43, 1984. 

Hypomagnesemia Loop diuretics increase the urinary excretion of magnesium. Hypocalcemia Serum calcium levels may be lowered (rare cases of tetany have occurred). 

Renal toxicity is the major potential toxicity of cisplatin. Severe nausea and vomiting that often accompany cisplatin administration may necessitate hospitalization. Cisplatin has mild bone marrow toxicity, yielding both leukopenia and thrombocytopenia. Anemia is common and may require transfusions of red blood cells. Anaphylactic allergic reactions have been described. Hearing loss in the high frequencies (4000 Hz) may occur in 10 to 30% of patients. Other reported tox-icities include peripheral neuropathies with paresthesias, leg weakness, and tremors. Excessive urinary excretion of magnesium also may occur. 

Reduction in urinary excretion of calcium and magnesium by postmenopausal women (12)... 

Calcium and magnesium homeostasis is altered by chronic diuretic therapy. Loop diuretics increase the urinary excretion of Ca2+ and can lead to stone formation. Thiazide administration, on the other hand, has the opposite effect and causes frank hypercalcaemia in some patients. Both thiazide and loop drugs increase the urinary loss of Mg2+ and this has been associated with cardiac arrythmias in the elderly. 

This transporter is selectively blocked by diuretic agents known as "loop" diuretics (see later in chapter). Although the Na+/K+/2Cr transporter is itself electrically neutral (two cations and two anions are cotransported), the action of the transporter contributes to excess K+ accumulation within the cell. Back diffusion of this K+ into the tubular lumen causes a lumen-positive electrical potential that provides the driving force for reabsorption of cations—including magnesium and calcium—via the paracellular pathway. Thus, inhibition of salt transport in the TAL by loop diuretics, which reduces the lumen-positive potential, causes an increase in urinary excretion of divalent cations in addition to NaCI. 

These studies indicate an intimate relation between the magnesium level of the diet and the pyridoxine requirement. It is suggested (A6) that, insofar as growth and urinary excretion of citrates, oxalates, and xanthurenic acid are concerned, high levels of magnesium appear to have a sparing effect on very low dietary levels of pyridoxine. 

For the authors (PIO) the simplest explanation of the data on tryptophan metabolism in these 3 patients would be as follows in scleroderma (acrosclerosis) there was an abnormal urinary excretion of kynurenine and its metabolites after oral ingestion of tryptophan. The administration of pyridoxine or pyridoxine plus nicotinamide partially corrected the metabolic abnormality. The efficacy of pyridoxine plus Na2EDTA could be explained on the basis of a decrease in tissue calcium and zinc (and possibly other cations), enabling the metal ions, normally functioning with pyridoxal phosphate, as magnesium ions, to be utilized more advantageously. 

Edetic acid is a metal chelator. The effect of an intravenous dose of 1 g of calcium disodium edetate on the urinary excretion on the elements aluminium, boron, barium, calcium, copper, iron, lead, magnesium, manganese, phosphorus, potassium, sihcon, sodium, strontium, sulphur, and zinc was measured in healthy volunteers. The ratio of the increase of urinary elimination was about two for iron, five for aluminium, lead, and manganese, and 15 for zinc (1). 

As a consequence of the blockade of the Na, K, 2Cr-cotransporter, the diuresis produced by furosemide (frusemide) results in increased urinary excretion of sodium, potassium, chloride, calcium and magnesium ions. The losses of sodium, potassium and chloride are approximately 1750, 600 and 2150 mmol, respectively, after i.m. administration of furosemide (frusemide) at 1 mg/kg. Although these electrolyte losses are substantial, they are largely replaced (within the 24 h period following furosemide (frusemide) administration) by enhanced renal reabsorption as well increased ion absorption from the intestinal tract. In addition to this primary action, furosemide (frusemide) may have a lesser inhibitory effect on other chloride ion transporters and the drug can also inhibit carbonic anhydrase activity (Martinez-Maldonado Cordova 1990, Rose 1989,1991, Wilcox 1991). Finally, some of the renal and extrarenal effects of furosemide (frusemide) appear to be mediated through increased prostaglandin production. 

With the onset of starvation, aldosterone secretion increases with the results of increased urinary excretion and decreased plasma concentration of potassium. Magnesium, calcium, and phosphate are affected similarly, although the urinary excretion of phosphate gradually declines. The absolute urinary excretion of ammonia and creatinine increases with prolonged starvation but that of urea decreases. 

Kohler and Pechet (K4) studied the changes in the urinary excretion of calcium, phosphorus, magnesium, °Sr, and hydroxyproline in intact and thyroparathyroidectomized rats in which the bones had previously... 

Maintenance of fluid volume, osmolarity, electrolyte balance, and acid-base status are aU regulated in large part by the kidney. Homeostasis of sodium, potassium, chloride, calcium, magnesium, and phosphorus is altered due to changes in urinary excretion that occur in patients with impaired kidney function. A comprehensive discussion... 

Patients undergoing OLT receive a substantial amount of crystalloid and blood products during the operative procedure. This often results in an edematous state in the postoperative period, especially in patients who had ascites preoperatively. The large citrate load from administered blood products has been implicated in causing hypocalcemia (due to citrate binding of ionized calcium) and metabolic alkalosis (due to conversion of citrate to bicarbonate) in the postoperative period. Low serum concentrations of magnesium are common in the postoperative period. Reduced intake from restricted diets and increased urinary excretion secondary to cyclosporine therapy contribute to hypomagnesemia. 

The seminal study by English et al clearly showed that major proximal tubular functions were preserved in acute CsA nephrotoxicity [15] and in fact, documented ATN is rarely seen in CsA-treated patients. On the other hand, experimental and clinical studies provided evidences of more subtle CsA-induced tubular cell injury like increased urinary excretion of tubular enzymes, increased fractional excretion of magnesium in the presence of hypomagnesemia, impaired urinary concentrating ability and hyperkalemia consequent to impaired tubular excretion of potassium [209,230,231]. Experiments using cultured LLC-PKl and MEKTK re-... 

Bushinsky da (1999) Calcium, magnesium and phosphorus renal handling and urinary excretion. 

When 5 healthy subjects took a single 600-mg dose of rifampicin with various antacids the absorption of rifampicin was reduced. The antacids caused a fall in the urinary excretion of rifampicin as follows 15 or 30 mL of aluminium hydroxide gel 29 to 31% 2 or 4 g of magnesium trisilicate 31 to 36% and 2 g of sodium bicarbonate 21%. ... 

A study in 10 patients taking chlorpromazine 600 mg to 1.2 g daily showed that 30 mL of Aludrox (aluminium/magnesium hydroxide gel) reduced their urinary excretion of chlorpromazine by 10 to 45%. ... 

In 6 healthy subjects magnesium trisilicate 5 g in 100 mL of water considerably reduced the bioavailability of a single 1-mg oral dose of dexamethasone. Using the urinary excretion of 11-hydroxycorticosteroids as a measure, the reduction in bioavailability was about 75%. ... 

Human studies have shown increased urinary excretion and decreased calcium and magnesium absorption in women administered the minerals and caffeine at the same time (Bergman et al. 1990 Heaney and Recker 1982), although an epidemiological study of approximately 1000 people over age 30 indicated a higher bone mineral density in persons who had habitually consumed tea for 19 years or more, as compared with nonhabitual tea drinkers (Nesher etal.2003). 

The determination of magnesium in urine (Table 3) is helpful in the investigation of hypomagnesemia. If the urinary excretion is increased, hypomagnesemia is probably due to renal insufficiency. However, if the excretion is decreased, an extrarenal cause... 

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