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The design, synthesis, and biological evaluation of amideless desferrioxamine analogues are described. The design concept is predicated on the idea that a low molecular weight desferrioxamine analogue would represent a better pharmacophore from which to construct an orally effective or more efficient trihydroxamate than the parent chelator. The study demonstrates that (1) the monohydroxamate units of desferrioxamine must be linked to promote iron clearance, (2) the N-propanoyl-N-pentyl fragments of desferrioxamine can be replaced with smaller, e.g., C-5, methylene units without compromising the analogue's iron-clearing properties, and (3) a delicate balance exists between the molecule's iron-clearing efficiency and its lipophilicity.

From August 1989 to May 1991, 52 patients with transfusion dependent thalassaemia major received L1 (1,2-dimethyl-3- hydroxypyrid-4-one), the oral iron chelator, for a period of 3-21 months (mean +/- SD: 14.2 +/- 6.8). Mean (+/- SD) urinary iron excretion varied from 6.2 +/- 4.6 mg/d on 25 mg/kg/d of L1 to 42.3 +/- 37.1 mg/d on 100 mg/kg/d of L1. Mean (+/- SD) drop in S ferritin was 1465 +/- 990 micrograms/l after 5.0 +/- 0.8 months to 3641.2 +/- 2299.3 micrograms/l after 20.1 +/- 0.9 months of therapy. There was no evidence of neutropenia, thrombocytopenia, ear or eye toxicity. L1-related arthralgia, which was reversible on dose reduction or stoppage, was seen in 20 patients (38.5%), while minor gastrointestinal (GI) tract symptoms occurred in seven (3.5%) cases. We conclude that although L1 is an effective iron chelator, further studies are required to understand the mechanism of L1 related arthralgia and also to find a safer but effective dose on which incidence of L1 related arthralgia is minimal.

This study was carried out in rats with nephrotoxic serum nephritis after autologous phase proteinuria was well established to determine the effect of tubule fluid iron chelation on the course of this disease. Deferoxamine administration caused a reduction in urinary iron potentially capable of catalyzing hydroxyl radical (.OH) formation and kidney iron uptake (224 +/- 60 vs. 398 +/- 152 mg/kg). This was associated with a decrease rate of progression of renal failure over the 21-day study period (creatinine clearance -0. 199 +/- 0.152 vs. -0.509 +/- 0.336 ml/min, P < 0.05) and improved survival (8/8 vs. 4/8, P < 0.05). In addition deferoxamine caused a reduction in urinary transferrin excretion (32 +/- 15 vs. 74 +/- 16 mg/day) and fractional excretion of transferrin (2.01 +/- 1 vs. 5.9 +/- 3.7%) and an increase in serum transferrin levels (229 +/- 36 vs. 139 +/- 45 mg/dl, all P < 0.05). It is suggested that iron presented to the tubule fluid as a result of the glomerular leak for transferrin is dissociated from transferrin. In turn the iron is available in a form capable of catalyzing .OH formation, resulting in lipid peroxidation of tubule cell membranes. Deferoxamine chelation of tubule fluid iron retards the development of both tubulointerstitial injury and superimposed glomerular sclerosis in this model of membranous nephropathy.

Measurements of iron absorption and incorporation into RBCs were obtained with the stable isotope 58Fe, administered as a reference dose, in 11 premature infants with birth weights between 780 and 1,520 g and gestational ages between 24 and 33 weeks. Each study included a timed stool and urine collection, nasogastric tube administration of a single dose of about 228 micrograms of 58Fe/kg of body weight (as FeSO4, with 10 mg/kg of vitamin C) between feedings, and blood samples before 58Fe (day 1) and then 2 weeks (day 15) later. Gastrointestinal absorption of the 58Fe dose as measured by fecal isotope balance was 41.6 +/- 17.6% (mean +/- SD). However, only 12.0 +/- 9.6% of the 58Fe dose (28.7 +/- 22.3% of the absorbed 58Fe dose) was incorporated into RBCs on day 15. 58Fe absorption and 58Fe incorporation into RBCs on day 15 were significantly correlated with the hemoglobin concentration and reticulocyte count on day 1. Transfusion history did not affect 58Fe absorption or 58Fe incorporation into RBCs. We conclude that concurrent measurement of 58Fe absorption with fecal monitoring and of 58Fe incorporation into RBCs permits a better understanding of the fate of iron ingested by premature infants than either measurement alone.

A new regimen of 24-hr ambulatory continuous intravenous infusion of deferoxamine (CIV DFO) through central venous ports was instituted in nine patients aged (mean +/- SD) 22.4 +/- 5.8 years over a period of 15.7 +/- 7.3 months. Central venous infusion sites were changed weekly in the clinic, eliminating the necessity for reconstitution of DFO and needle insertion at home. Because CIV DFO could be interrupted only by medical personnel, patient compliance was documented accurately; patients administered 93.0% +/- 3.2% of CIV DFO prescribed. Mean urinary iron excretion on CIV DFO (66.8 +/- 50.4 mg/24 hr) was significantly greater than that quantitated during 12-hr equivalent-dose subcutaneous DFO infusions (23.4 +/- 18.3 mg/24 hr; P less than 0.025). Mean serum ferritin declined by 71% over the treatment period (P less than 0.005). This regimen confers the advantages of uninterrupted exposure to DFO, is associated with excellent patient compliance, and should be considered in any patient with severe iron overload and erratic compliance with DFO.

Eleven patients with beta thalassemia major were entered into the trial of the oral chelator 1,2-dimethyl-3-hydroxypyrid-4-one (L1). Their ages ranged from 17 to 26 years (mean +/- SD, 22.3 +/- 2.7). Six were male and five were female. L1 was administered at an initial daily dose of 42.5 to 60 mg/kg as a single dose. After 4 weeks, the dose was increased to 85 to 119 (102 +/- 10.7) mg/kg for 191 to 352 days divided into either two or four doses daily, except for one patient who developed agranulocytosis after 11 weeks and was taken off the trial. Initial serum ferritin values in the remaining 10 patients ranged between 1,000 and 9,580 (5,549 +/- 3,333) micrograms/L and at end of the trial their mean serum ferritin was significantly lower (4,126 +/- 2,278; P less than .05 using the paired t-test). Urinary iron excretion at a daily dose of 85 to 119 mg/kg administered as two divided doses ranged between 0.14 and 0.82 (0.44 +/- 0.26) mg/kg/24 h. In three patients, the four doses per day schedule caused substantially more iron excretion than the same total dose divided into two. During the course of the trial, several possible adverse effects have been encountered. One patient (female, aged 20) developed agranulocytosis 11 weeks after starting treatment and 6 weeks after beginning treatment with a daily dose of 105 mg/kg. This patient's neutrophil count recovered spontaneously 7 weeks after the discontinuation of L1. A decrease in serum zinc levels to subnormal levels was observed in four patients with symptoms of dry skin, with an itchy scaly rash in two that was associated with low serum zinc levels that responded to zinc therapy. Urinary zinc levels ranged from 4.7 to 23.4 (13 +/- 5.5) mumol/24 h and were above 9 mumol/24 h (upper limit of normal) in eight patients. Mild nausea occurred in three patients and transient diarrhea in a fourth. Mild musculoskeletal symptoms occurred in three patients but settled without discontinuation of L1 therapy in two and with temporary discontinuation of L1 in the third. A transient increase in serum aspartate transaminase was also noted in five patients, but serum aspartate transaminase levels subsequently decreased in all of them. No cardiovascular, neurologic, renal, or retinal toxicities were demonstrable. These results confirm that L1 is an effective oral iron chelator. Further clinical trials are needed to determine the incidence and severity of adverse effects.

The efficacy and toxicity of the siderophore desferrithiocin (DFT), which has shown potential application in iron chelation therapy, were assessed in vivo and in vitro. DFT was evaluated in vivo in two ways: firstly, by measuring the effect of a single dose of DFT (10-100 mg/kg) on 59Fe excretion in iron-loaded rats labelled with 59Fe; and secondly, by examining the effect of the daily oral administration for 2 weeks of DFT (10-25 mg/kg/d) on the growing rat. DFT and its ferric complex, ferrithiocin (FT), were assessed in vitro from their effects on transferrin and iron uptake and mobilization from rat hepatocytes in culture using transferrin doubly labelled with 125I and 59Fe. Both oral and subcutaneous DFT were highly effective in promoting iron excretion in vivo, but showed evidence of toxicity after oral administration for 2 weeks at 25 mg/kg/d. In addition, DFT was much more effective than desferrioxamine or pyridoxal isonicotinyl hydrazone in reducing hepatocyte iron in vitro. However, FT was cytotoxic, causing membrane disruption and release of intracellular aspartate aminotransferase. It was concluded that DFT should not be considered for chronic iron chelation therapy without extensive further evaluation.

In patients with thalassemia intermedia in whom hyperabsorption of iron may result in serious organ dysfunction, an orally effective iron-chelating drug would have major therapeutic advantages, especially for the many patients with thalassemia intermedia in the Third World. We report reduction in tissue iron stores and normalization of serum ferritin concentration after 9-month therapy with the oral chelator 1,2-dimethyl-3-hydroxypyrid-4-one (L1) in a 29-year-old man with thalassemia intermedia and clinically significant iron overload (SF 2,174 micrograms/L, transferrin saturation 100%; elevated AST and ALT, abnormal cardiac radionuclide angiogram) who was enrolled in the study with L1 75 mg/kg/day after he refused deferoxamine therapy. L1-Induced 24-hour urinary iron excretion during the first 6 months of therapy was (mean +/- SD, range) 53 +/- 30 (11 to 109) mg (0.77 mg/kg), declining during the last 3 months of L1 to 24 +/- 14 (13-40) mg (0.36 mg/kg), as serum ferritin decreased steadily to normal range (present value, 251 micrograms/L). Dramatic improvement in signal intensity of the liver and mild improvement in that of the heart was shown by comparison of T1-weighted spin echo magnetic resonance imaging with images obtained immediately before L1 administration was observed after 9 months of L1 therapy. Hepatic iron concentration decreased from 14.6 mg/g dry weight of liver before L1 therapy to 1.9 mg/g liver after 9 months of therapy. This constitutes the first report of normalization of serum ferritin concentration in parallel with demonstrated reduction in tissue iron stores as a result of treatment with L1. Use of L1 as a therapeutic option in patients with thalassemia intermedia and iron overload appears warranted.

The effect of caloreen (glucose polymer) supplementation on indicators of iron status during protein-energy malnutrition was studied. Sixty-four children with moderate protein energy malnutrition (PEM) were fed diets supplemented with caloreen or starch (control) for 14 days, following which iron status as packed cell volume (PCV), haemoglobin (Hb), serum iron, total iron binding capacity (TIBC), serum ferritin, and urinary iron levels were determined. Caloreen supplementation significantly increased (P less than 0.05). PCV, serum iron and serum ferritin and decreased (P less than 0.05) TIBC. Also, there was a tendency for Hb to increase and urinary iron to decrease in this group, but these changes were not statistically significant. Such changes were not observed in the starch-placebo-supplemented group. It is concluded that caloreen supplementation to PEM children increases body iron status. These increases in the indices of iron status may contribute to an early recovery of anaemia associated with PEM. Prolonged supplementation of a regular diet with glucose early in the development of PEM may retard the development and severity of anaemia in children.

The utilization of selected minerals when sugars were supplemented to basal diets was investigated in two separate, laboratory-controlled human feeding studies. Fructose-fed subjects had higher fecal excretions of iron and magnesium than did subjects fed sucrose. Apparent iron, magnesium, calcium, and zinc balances tended to be less positive during the fructose feeding period as compared to balances during the sucrose feeding period. Conversely, high fructose corn syrup (HFCS) did not affect the mineral balances when compared to sucrose feeding. Subjects fed fructose experienced diarrhea which possibly decreased absorption of minerals and thus increased fecal mineral losses. No such adverse effects were noticed when HFCS was fed.

A comparative study of the iron-clearing properties of subcutaneously (SC) administered deferoxamine (DFO) with those of orally administered 1,2-dimethyl-3-hydroxypyrid-4-one (CP20) and 1,2-diethyl-3-hydroxypyrid-4-one (CP94) is presented. The studies were performed in both a non-iron-overloaded, bile duct-cannulated rat model and an iron-loaded Cebus monkey model. All three drugs performed well in the rodent, promoting the excretion of iron in both the urine and the bile, with total iron output efficiencies of 2.8%, 1.2%, and 7.1%, respectively. The efficiency of DFO increased slightly in the Cebus model, while that of the hydroxypyridones was essentially the same in the monkey, with total iron output efficiencies of 5.5%, 2.1%, and 7.4%, respectively. Iron balance studies showed that both DFO and CP94 were able to maintain the animals in a negative iron balance, while CP20 had little impact.

Experimental hepatosis induced by intragastric administration of CCl4 was revealed to be accompanied by changes in temporal organization of lipid peroxidation, sideremia and iron excretion with urine. Even at early stages of organ lesions, the activation of free-radical lipid oxidation and rearrangement of sideruria circadian rhythm were found to result in a substantial and stable increase in mesor of the trace element excretion with urine in spite of a statistically significant decrease in water release.

The mechanism of in vivo iron chelation by 3-hydroxypyridin-4-ones (CP compounds) was studied in hypertransfused rats in which the major storage iron pools in hepatocytes and in the reticuloendothelial (RE) system have been labeled by selective radioiron probes. Both dimethyl-3-hydroxypyridin-4-one (CP 20 or L1) and diethyl-3-hydroxypyridine-4-one (CP 94) have an identical and very high (log beta 3 36) binding constant and selective affinity to iron(III), but the lipid solubility of CP 94 is considerably higher than that of CP 20. Both chelators induced an increase in the fecal excretion of hepatocellular iron with no effect on urinary excretion. In contrast, about one third to one half of the iron mobilized from RE cells was excreted in the urine. The chelating efficiency of CP 20 was comparable with that of deferoxamine (DF), whereas CP 94 was up to eight times more effective than DF. Unlike DF, which had no effect by the oral route, the oral and parenteral effectiveness of both CP compounds was identical. These findings indicate that: (1) lipid solubility is an important determinant of in vivo chelating efficiency; (2) urinary iron excretion induced by the CP compounds is derived from RE cells; (3) part of the iron mobilized from RE cells and all of the iron derived from hepatocytes is excreted through the bile; and (4) contrary to previous observations in cell cultures, there is no in vivo evidence for a diminishing chelating efficiency at the lowest doses used.

A new oral iron chelator, L1, was given for 14 to 16 months to four patients with transfusion haemosiderosis. These patients could no longer be treated with deferoxamine because of allergic reactions or psychological problems. Serum ferritin values at the start of the treatment ranged from 2220 to 4530 microgram/l. L1 was given in a total daily dose of 3 g, at first in a single dose, later 3 times 1 g daily. The 24-hour urinary excretion of iron varied greatly from day to day. The mean urinary iron excretion of the four patients ranged from 19.3 to 45.7 mg/day. In two patients an important decrease of ferritin was found. These patients had been given no more or only sporadic transfusions. In one patient transient agranulocytosis was seen which was probably not caused by L1.

The purpose of this study was to determine disorders in the metabolism of the essential elements (Ca, Fe, Cu, and Zn) in some tissues of rats, as well as to detect the dynamics of urinary excretion of these metals after oral administration of 20 mgAl/kg every day for 8 wk. The elements were determined in brain, kidneys, blood, and urine of the animals in 1st, 2nd, 3rd, 4th, and 8th wk after the exposure to AlCl3. After the 1st wk of aluminium administration, we observed increase of Ca and a decrease of Fe in blood. In brain Ca, Fe, and Cu concentrations were significantly higher in Al-treated rats than in controls after 8-wk exposure. The concentration changes of the essential metals in the tissue were accompanied by increase of the Ca, Fe, and Zn urinary excretion. We assume that the increase in urinary excretion of Ca and the decrease of Fe in the blood may be sensitive indicators of oral aluminium administration.

The present study was undertaken to determine urinary and serum iron, transferrin and albumin levels in diabetic patients with varying amounts of proteinuria. A highly significant correlation was found between urinary albumin and transferrin excretion over a wide range of urinary albumin excretion (0.005 to 18 g/g creatinine) (r = 0.972). The urine/serum ratio of transferrin and albumin were identical, documenting a similar glomerular leak and tubule handling for these two proteins. In contrast to the above correlation between transferrin and albumin, there was no correlation between iron and either of these proteins until nephrotic range proteinuria had occurred, and even at that time the correlation was much weaker than that found between the proteins (r = 0.680). Urinary iron excretion increased early in the course of diabetic renal disease, being increased in 3 of 11 patients without proteinuria and in 8 of 10 patients with mild proteinuria. All patients with nephrotic range proteinuria had markedly increased urinary iron excretion (150 +/- 166 micrograms/g creatinine vs. 6.4 +/- 0.7 micrograms/g creatinine in controls) and decreased serum iron levels (592 +/- 189 micrograms/liter vs. 979 +/- 394 micrograms/liter in the control group). The iron/transferrin ratio in urine was consistently greater than the iron/transferrin ratio in plasma at all stages of proteinuria. In patients with both subnephrotic and nephrotic range proteinuria, approximately 35 to 40 micrograms Fe/g creatinine was present in the urine with an excess of transferrin. In conclusion, urinary iron excretion is increased early in the course of diabetic renal disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Study Objective: The aim was to determine whether the potent iron chelator desferrioxamine, previously shown by our laboratory and others to cause acute limitation of infarct size, would provide sustained protection against myocardial ischaemia-reperfusion injury., Design: Anaesthetised dogs underwent a 2 h transient coronary artery occlusion. After surgical preparation, each dog was randomised into one of two groups receiving either desferrioxamine or equivalent infusion of saline. Infusion of desferrioxamine was initiated 30 min before occlusion at an initial dose of 10 mg.kg-1 for the first hour of the protocol, followed by a maintenance dose of 1.5 mg.kg-1.h-1 throughout the remainder of the ischaemic period and the initial 4 h of reperfusion. The animals were reanaesthetised the following day and killed 20-24 h following reperfusion. Variables measured included heart rate and arterial pressures; regional myocardial blood flow; urinary iron content; and infarct size. In addition, % wall thickening in the ischaemic-reperfused myocardium was assessed by echocardiography in a limited number of animals., Experimental Material: 12 mongrel dogs weighing 22(SEM 4) kg were used, n = 6 in each group., Measurements and Main Results: Both groups were equally and severely ischaemic during coronary artery occlusion. Desferrioxamine caused a modest and transient reduction in mean arterial pressure during the ischaemic episode, but had no effect on heart rate or myocardial blood flow. As expected, urinary iron content was significantly higher in treated animals v controls, at 465(SEM 107) v 55(23) micrograms, p less than 0.01, indicating that desferrioxamine effectively chelated free iron. However, it failed to exert a significant cardioprotective effect: infarct size did not differ between control and treated groups [54(4)% v 58(5)% of the myocardium at risk], and wall thickening was similar throughout occlusion and reperfusion in control and desferrioxamine treated animals., Conclusions: Despite substantial reduction in infarct size previously observed at 4 h following reflow with the same dose and regimen of desferrioxamine treatment, results of the present study indicate that desferrioxamine did not provide sustained protection against myocardial ischaemia-reperfusion injury. We therefore conclude that desferrioxamine delays--but does not prevent--myocyte necrosis in this canine model.

Single-dose and steady-state pharmacokinetics of the new oral iron chelator, 1,2-dimethyl-3-hydroxypyrid-4-one (L1) were studied in 14 patients with thalassemia and correlated with iron excretion. Food prolongs the rate of absorption of L1, but it does not affect significantly the extent of absorption measured by the area under the plasma concentration-time curve. Similarly, it does not affect the chelation potential of the drug. The mean elimination half-life of the drug is 3 hours, suggesting that a divided dose every 8 hours may assure better chelation. Our steady-state studies reveal that urinary iron excretion is independently influenced by body iron load (measured by ferritin levels) and by steady-state trough concentrations of the drug. While patients were receiving an unchanged regimen of 75 mg/kg/day, we have detected a gradual and significant decrease in trough concentrations in the presence of unchanged patients' compliance monitored by the Medication Event Monitoring System, diaries, and pill count. These findings suggest self-induction of L1 metabolism or decreased absorption during long-term therapy. Because of the concentration-dependent iron excretion, patients may need increasing doses to achieve negative iron balance.

Desferrithiocin, a novel microbial siderophore isolated from cultures of Streptomyces antibioticus DSM 1865, and a number of its derivatives and analogues are evaluated for their ability to promote iron clearance. The compounds have been designed with the objective of identifying the structural features of desferrithiocin which render this ligand an orally effective iron chelator. The desferrithiocin aromatic hydroxyl and the thiazoline ring carboxyl group are shown to be central to desferrithiocin's activity. The ligand's methyl and the aromatic nitrogen play little role in the compound's efficacy. The animal model chosen for this study, the bile duct cannulated rat, provides information regarding both the chelator-induced total iron output and the kinetics of both biliary and urinary iron excretion.

The criteria for the cessation of deferoxamine therapy in the acutely iron poisoned patient are vague and imprecise. We have developed a urinary iron assay which is not confounded by the presence of deferoxamine and have established a reference range in non-iron poisoned deferoxamine treated human volunteers. When reported as a urine iron to creatinine ratio the results from isolated urine specimens can be utilized to guide deferoxamine therapy. This method is rapid, simple and inexpensive and utilizes equipment and reagents found in laboratories already providing emergency serum iron concentrations. We have found this assay to be useful as a criterion for the cessation of deferoxamine therapy in the acutely iron poisoned patient and as an objective indicator of a positive deferoxamine chelation challenge.

The effects of different nickel chloride doses upon blood and plasma glucose and essential metal homeostasis were studied in male and female rats. A definite sex-dependent response to injections of nickel has been observed for both the increase in plasma and blood glucose levels and the time at which these levels peak. Males showed a fast recovery from the rise in glucose levels and were much less affected by changes in the other parameters studied. In females, an extended rise in glucose levels was observed. All these effects are clearly nickel dose-dependent. Plasma, liver and kidney copper levels rose significantly in females while only a small decrease was observed in male kidneys. Zinc levels rose in all organs studied but males recovered to basal levels after the study period, whereas females maintained maximum levels at the end of the same period. An increase in urinary excretion of iron was observed. The present results show that the sex differences to acute nickel toxicity can be a helpful way to study metal interaction and discriminate between specific toxicity due to nickel or that induced by the associated hyperglucagonemia.

L1 was given to eight patients with beta-thalassaemia major who had previously been treated with deferoxamine (DF) for 4-10 years. The patients' ages ranged from 11 to 27 years. Serum ferritin values ranged from 1.3 to 11.5 x 10(3) micrograms/l. L1 was given twice daily at a daily dose of 55-80 mg/kg body weight and was continued for 10 months in two patients, 9 months in three, 7 months in two patients and 4 months in one patient. As previously observed with DF, each patient's urinary iron excretion (UIE) varied greatly from day to day. The mean UIE of the eight patients ranged from 11 to 49 mg/d (0.2-0.87 mmol/d) on subcutaneous DF and from 16 to 53 mg/d (0.28-0.95 mmol/d) on L1. Two patients excreted significantly more and one patient significantly less iron while on L1. If the UIE was calculated as mmol Fe/mmol creatinine there was no statistically significant difference. Serum ferritin values fluctuated widely in all, with a consistent downward trend in three, no change in four and an increase in one of two non-splenectomized patients. This patient's splenomegaly and need for transfusions continued to increase while on L1. No toxicities attributable to the drug were detected during the period of study and tolerance of the drug was excellent.

The efficacy of the oral iron chelator 1,2-dimethyl-3-hydroxypyrid-4-one (L1) was compared with that of subcutaneous desferrioxamine in 26 patients with transfusional iron overload. Immediately after red-cell transfusion, 20 patients were randomised to receive either desferrioxamine (50 mg/kg daily as a 12 h subcutaneous infusion), or L1 (50 mg/kg daily by mouth). Patients were evaluated during treatment with the other drug after transfusion the next month. Mean (SD) daily urinary iron excretion was lower during L1 than during desferrioxamine (12.3 [6.7] vs 18.2 [15.3] mg/day). In 5 patients the dose of L1 was raised from 50 to 75 mg/kg daily; mean urinary iron excretion rose from 13.8 (7.0) mg/day to 26.7 (17.8) mg/day, comparable with that during desferrioxamine (24.9 [24.3] mg/day). Faecal iron excretion rose slightly over baseline in 6 patients studied during L1 administration (from 8.5 [0.9] mg/day to 12.2 [0.9] mg/day). Pharmacokinetic studies showed an elimination half-life for L1 of 117-237 min. Studies in dogs and in volunteers showed no absorption of the L1-iron complex, excluding a contribution of absorption of intraluminal complexes of L1 and food iron to urinary iron excretion. Further animal toxicity testing is needed before L1 can be studied in a broader group of patients.

A long-term clinical trial of 1-15 months has been carried out with the oral iron chelator 1,2-dimethyl-3-hydroxypyrid-4-one (L1) in 13 transfusion-dependent iron-loaded patients. Urinary iron excretion was greatest in patients with thalassaemia major and was related to the number of previous transfusions but not to the serum ferritin level. Substantial increases of urinary iron were observed in all the patients when the frequency of the daily dose was doubled and in response to 2 x 3 g L1 daily 11 of 12 patients tested excreted greater than 25 mg iron daily, the mean daily intake of iron from transfusion. Serum ferritin levels have fluctuated but overall have remained unchanged. Pharmacological studies in five patients have indicated rapid absorption probably from the stomach and variable plasma half life of 77 +/- 35 min (X +/- SD). Glucuronation was identified as a major route of L1 metabolism. Short-term intensive chelation studies using repeated administration of L1 resulted in further increases of urinary iron excretion by comparison to a single dose. In one case 325 mg of iron were excreted in the urine following the administration of 16 g (5 x 2 g + 2 x 3 g) within 24 h. Iron excretion studies were carried out in six transfusional iron-loaded patients who were maintained on a low iron diet before and during chelation. No significant increases of faecal iron excretion were observed with L1 using daily doses of up to 3 x 3 g and 4 x 2 g. The high level of compliance during treatment with L1 and the levels of urine iron excretion that can be achieved increase the prospects for oral chelation in transfusional iron-loaded patients.

Pharmacokinetic studies have been carried out with the oral iron chelator 1,2-dimethyl-3-hydroxypyrid-4-one (L1). HPLC analysis of serum of a normal volunteer and seven transfusional iron loaded patients who ingested a 3 gm dose of L1 revealed that L1 was most probably absorbed from the stomach and was transferred to the blood with a half-life of 0.7 to 32 minutes. L1 reached maximum concentration in the serum 12 to 120 minutes after administration with 85% to 90% elimination within the first 5 to 6 hours, with a half-life of 47 to 134 minutes. L1 and its glucuronide metabolite were identified in serum and urine but not in feces. In most cases hydrolysis of 24-hour urine samples with use of beta-glucuronidase resulted in almost complete recovery of the administered dose. Urinary iron excretion was proportional to the iron load but not to the serum or urine concentration of L1. The therapeutic efficiency of L1 can therefore be improved by repeated administration of 2 to 3 gm doses at least every 6 hours.

We have developed a simple, rapid method for analysing faecal iron using a microwave oven for digestion followed by atomic absorption spectrometry. The chelating effect of 1,2-dimethyl-3-hydroxy-pyrid-4-one (DMHP) has been tested in rats with experimental iron overloading and three routes of DHMP administration, oral, subcutaneous, and intraperitoneal, have been compared. Regardless of the route of administration, we have found that DMHP promotes iron excretion via the urine. We have not observed a difference in the amount of iron excreted in the faeces before and after DMHP administration by any route. The subcutaneous route of administration is the most effective in promoting iron excretion, followed by the intraperitoneal route. Although most convenient for clinical use, oral administration promotes the excretion of only a small fraction of that by the subcutaneous route.

In a group of 56 patients being evaluated for iron storage disease, all of whom underwent liver biopsy with quantitative measurement of liver iron concentration, urinary excretion of iron was measured following intramuscular injection of deferoxamine (10 mg/kg body weight). Urine was collected in two portions, 0-4 h and 4-24 h after deferoxamine administration. Iron excretion in the first 4 h was closely correlated to that over the entire 24-h period (r = 0.88, p less than 0.0001, 95% confidence interval = 0.80-0.93), indicating that the 4-h deferoxamine urinary excretion test can be adapted readily to an outpatient clinical setting, helping to insure complete and accurate urine collections. Correlation of 0- to 4-h urinary iron excretion and quantitative liver iron (r = 0.335), although higher than for the full 24 h (r = 0.192), was not sufficient to accurately predict hepatic iron concentration in the individual patient.

Iron plays a central role in bacterial infections, influencing both bacterial virulence and host cellular defense mechanisms. We investigated whether iron chelation might be of benefit in the treatment of pneumonic pasteurellosis of calves. Neutrophils obtained from calves previously treated with the iron chelator, deferoxamine, were studied for their responses to latex and opsonized zymosan by luminol-enhanced chemiluminescence and to phorbol myristate acetate and opsonized zymosan by superoxide generation. Treatment with deferoxamine in vivo failed to influence these in vitro measures of neutrophil oxidative metabolism. Furthermore, iron depletion with deferoxamine failed to modify the pathophysiological derangements that occurred in calves following experimental induction of pneumonia by intratracheal inoculation with Pasteurella haemolytica. These data indicate that iron chelation using deferoxamine cannot be recommended as an adjunct to conventional therapy in the treatment of pneumonic pasteurellosis of cattle.

The morphologic aspects of iron overload have been studied in human subjects, mammals, and birds with spontaneous overload, in a variety of experimental animals, and also in cell cultures. Reviewed here are the contributions of electron microscopy to the understanding of the iron-loading process, as reported during the last 12 years. The electron-density of ferrihydrite cores located within the protein shell of the ferritin molecule enabled its identification within either cytosol or lysosomes (siderosomes) of iron-exposed cells. The process of (holo)ferritin assembly, its transfer into siderosomes, and its degradation to hemosiderin can be followed in various cells. Siderosomes display cell-line-specific ultrastructural features, and different cell types show varying iron-segregating capacity. The study of experimental animals and cultured cells show that an iron-rich milieu may be damaging, probably through iron-catalyzed lipid peroxidation. Recent ultrastructural studies stress the value of describing initial alterations as opposed to the irrelevant end-stage findings. Further efforts should be directed toward elucidating the origin of iron in neonatal hemochromatosis, the role of iron in infection and neoplasia, and the nature and role of brain iron.

"High-performance" liquid-chromatographic (HPLC) methods have been developed for identifying 1-substituted 2-alkyl-3-hydroxypyrid-4-one iron chelators in serum and urine. Ion pairing with heptane- or octanesulfonic acid in pH 2.0-2.2 phosphate buffer and reversed-phase chromatography were required to separate these compounds from endogenous compounds in both biological fluids. In both the 2-methyl and 2-ethyl series of 1-substituted compounds (H, methyl, ethyl, or propyl) the elution times increased in accordance with the n-octanol/water partition coefficients (propyl greater than ethyl greater than H greater than methyl). Urine samples were filtered (0.4 microns pore size) and injected either undiluted or after dilution with elution buffer. After the addition of internal standard, the plasma or serum samples were deproteinized by treatment with HCIO4, 0.5 mol/L, centrifuged, and the supernates were injected directly onto the HPLC. Using these procedures, we could identify 1,2-dimethyl-3-hydroxypyrid-4-one (L1) in the serum and urine of a thalassemic patient who had received a 3-g dose of the drug and in the urine of other patients who had received the same dose. One or more possible metabolites were also observed in the chromatograms of both urine and serum. The 24-h urinary output of L1 (0.22-2.37 g) and iron (10.6-71.5 mg) varied but there was no correlation between the two with respect to quantity or concentration. Instead, urinary iron output was higher in patients with a greater number of transfused units of erythrocytes. This is the first study in humans to show that L1 is absorbed from the gut, enters the circulation, and is excreted in the urine.

The characteristics of iron stores built up by a new parenteral iron-poly (sorbitol-gluconic acid) complex, Ferastral, have been studied in iron depleted non-anemic blood donors. The results from studies on the first three subjects are presented. The availability of this storage iron for the chelator, desferrioxamine, was found to be in the same range as normal iron stores. The pattern of distribution in reticulo-endothelial cells of the bone marrow could not be differentiated from natural storage iron. No visible iron could be detected in liver parenchymal cells 40 days after iron administration. The results from these preliminary studies suggests normal bioavailability of this material for Hb-synthesis. The absence of iron in liver parenchymal cells might be explained by the short time interval between the iron administration and the fine needle aspiration biopsy.

Subcutaneous infusions of Desferal (DF) rarely induce negative iron balance in thalassemia major patients less than 6 years old. In nonsplenectomized patients the requirements for blood transfusions increase slightly. Urinary iron excretion decreases during the first days following a blood transfusion. An average of 5.8 mg/day equivalent to 30% of the total iron excretion is eliminated with the feces after subcutaneous infusions of DF. Serum ferritin does not decrease significantly after 18-24 months of therapy. The effectiveness of long-term therapy progressively increases in the splenectomized patients, while it decreases appreciably in the course of the treatment in the nonsplenectomized ones.

The metabolism of iron-poly (sorbitol-gluconic acid) complex (Ferastral) was studied in 6 blood donors with latent iron deficiency and 13 patients with manifest iron deficiency anaemia. Between 125 and 1 000 mg of iron were injected. In latent deficiency an average of 19% of the dose given was excreted during the first two weeks. The corresponding figure for patients with manifest iron deficiency was 11%. An average of 8% of the dose was retained at the site of injection after 40 days. In the two groups, respectively, 61% (range 47%-70%) and 58% (range 24%-86%) of the iron retained was incorporated into red cells after 40 days, which is judged to be quite satisfactory. Some local side effects were observed.

Twenty-eight children with beta-thalassaemia major aged between 11 and 48 months were given intensive transfusions. Serum iron, transferrin saturation, serum ferritin, non-transferrin iron, and subcutaneous desferrioxamine-induced urinary iron excretion were measured. The results showed that even children with a limited number of transfusions had severe iron overload as indicated, in particular, by the raised serum ferritin levels and the high excretion rates after subcutaneous infusion of desferrioxamine. The desferrioxamine test was useful, even in very young children, in assessing response to chelation therapy thus enabling such treatment to be started early to prevent harm from iron overload.

2,3-Dihydroxybenzoic acid has been identified as a potentially useful iron-chelating drug. Accordingly, we have evaluated a series of derivatives of hydroxylated benzoic acids for their ability to induce iron excretion in the iron-overloaded rat. In addition, we have examined a number of hydroxamic acids and some other naturally occurring iron-chelating agents. Of the 26 benzoic acid derivatives studied, none appeared to be more effective than 2,3-dihydroxybenzoic acid, for reasons which are discussed. Rhodotorulic acid, a hydroxamic acid produced by and isolated from cultures of Rhodotorula pilimanae, was the most effective of all the compounds studied in inducing iron excretion. When administered parenterally, rholotorulic acid induced iron excretion via both the urinary and the fecal routes and was more than twice as potent (on a weight basis) as desferrioxamine. Two ferrous chelators, alpha, alpha-dipyridyl ad 1,10-phenanthroline, induced a moderate amount of iron excretion, suggesting that a pool of ferrous iron may be available for chelation.

Levels of iron and unsaturated iron binding capacity in serum and the renal excretion of iron were studied in 15 anaemic patients receiving Ferastral. Various dose schedules were used, 100 mg Fe daily for 10 days, 200 mg Fe daily for 5 days, and 500 mg Fe twice at various intervals from 2 to 7 days. A continuous increase of iron in serum was seen after the doses 100 mg and 200 mg daily as well as after 500 mg given at intervals of 2 and 3 days. Longer 500 mg dose intervals resulted in a fluctuation in the iron concentration. Peak levels varied between 740 and 5 260 microgram/100 ml (132 and 942 mumol/1). A transient decrease in the UIBC was seen. Urinary excretion of iron varied between 8.9 and 26.9% of the dose given. No local or general side effects occurred.

The ascorbate status and the effect of loading doses of ascorbic acid (1,5 g per day by mouth for 7 days) on the porphyric process were studied in 7 black men with porphyria cutanea tarda symptomatica. It was found that the ascorbate stores were depleted in these patients as judged by serum and leucocyte ascorbate levels. Temporary repletion of the ascorbate stores was effected by the loading doses of ascorbic acid: Serum iron concentrations increased in 6 patients; urinary iron excretion showed small peaks a few days after ascorbic acid therapy commenced; haemoglobin concentration was not affected; excessive amounts of oxalate were excreted in the urine; neither total urinary porphyrin excretion nor the composition of the urinary porphyrins was affected in a way which could be related to ascorbate therapy. Further evidence that ascorbate depletion is not important in the induction of porphyria was found when the ascorbate status of siderotic rats, rendered porphyric by hexachlorobenzene-feeding, was examined. Stores of ascorbate and the oxidative catabolism of ascorbate were not different in the prophyric rats as compared with normal litter mates.

Two patients with long-standing nephrotic syndrome are described in whom urinary iron losses may have contributed towards an iron deficiency state. Seven other nephrotic patients were also studied. Increased urinary iron excretion was found in six out of nine patients and increased urinary copper excretion in all eight patients in whom it was measured. Trace metal losses in the urine in nephrotics may be important clinically.

Chronic refractory anemia associated with congenital hypoplastic anemia (CHA, Blackfan-Diamond syndrome) and with the 5q-syndrome may require chronic transfusion therapy to sustain life. Hemosiderosis and death from chronic iron overload may result from such a program. The effect of subcutaneous (SC) deferoxamine (DF) and supplemental oral vitamin C (vit. C) on urinary iron excretion was studied in two patients with congenital hypoplastic anemia and one patient with 5q-syndrome. In the two patients with CHA, urinary iron excretion in response to DF given SC over 24 hours was comparable to the results following intravenous (I.V.) administration. Both of these cases had low levels of plasma ascorbate on initial evaluation and excreted more iron in response to two different doses of DF after they had received supplemental vit C and their stores were repleted. Significant iron excretion occurred in all three patients for 12 hours during the SC infusion of DF and for 12 hours after the end of the infusion. In all three patients, increasing the dose of DF up to 3-4 g given SC over 12 hours resulted in a linear increase in iron excretion. Once normal body stores of ascorbate were achieved by oral supplementation, increasing doses of vit C did not appear to cause a further increment in iron excretion. DF administered by a slow SC infusion appears to be an effective approach to iron overload in patients with refractory anemia and hemosiderosis secondary to chronic transfusions. Only small amounts of supplemental vit. C necessary to sustain adequate body stores are required for optimal iron excretion.

Thirteen women, six of whom were using oral contraceptive agents, between the ages of 23 and 34 years, free from illness, and without a previous clinical history of menstrual abnormality, were studied with chronobiological methods for circadian (about 24 hour) patterns of metal and creatinine excretinine excretion. Circadian rhythms were detected for the excretion of lithium, potassium, iron, sodium, copper, and creatinine. Statistically significant by lower 24 hour excretion (mesors) of lithium, potassium, and iron was detected for the subjects using oral contraceptive agents. Although all women adhered to nearly identical activity-rest (synchronization) schedules, the peak times (acrophases) of the metal excretory rhythms for oral contraceptive users were phase delayed by about two hours.

The various erythrocyte indices, serum iron, unsaturated iron binding capacity, serum ferritin and sideruria after desferrioxamine were measured in a group of 30 patients with active Rheumatoid Arthritis and anemia. The patients were subdivided into two groups of 23 and 7 subjects based on the presence or absence of marrow iron stores, respectively. Significant differences in the mean values of unsaturated iron binding capacity (P less than 0.001), serum ferritin (P less than 0.01) and sideruria after desferrioxamine (P less than 0.001) were observed between the two groups of patients by statistical analysis. Unlike the other indices, the values assessed in the first and the second group of patients as for the above parameters did not overlap. A negative correlation index and a positive one of high significance (P less than 0.001) was found between the values of serum ferritin and those of unsaturated iron binding capacity and sideruria after desferrioxamine, respectively. The above results demonstrate that even in active Rheumatoid Arthritis a concomitant iron deficiency can be diagnosed by means of non-invasive, quantitative and easily reproducible methods.

Non-transferrin-bound iron (NTBI), a potentially toxic compound, is increased in the serum of patients with iron overload and fully saturated transferrin. We found markedly elevated NTBI levels in 16 children (including nine with sickle cell disease and five with beta-thalassemia) with iron overload secondary to prolonged transfusion therapy. During iron chelation with subcutaneous desferrioxamine infusion, NTBI levels decreased to normal, but became elevated within 2 to 4 hours after discontinuation of desferrioxamine. NTBI causes hepatic and cardiac toxicity in experimental systems, but our patients lacked sufficient organ dysfunction for this association to be made. The use of continuous 24-hour chelation to maintain NTBI at low levels may prevent progressive iron toxicity in patients who first received chelation therapy at an older age or who already have evidence of cardiac damage.