Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Absorption”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,783 records · Page 99Linked to original sources
PubMed1996

Applications and simulations of a discontinuous oral absorption pharmacokinetic model.

PURPOSE: To illustrate the application of a discontinuous oral absorption model to cimetidine and ranitidine plasma concentration versus time data to demonstrate the use of the model for drugs which display discontinuous oral absorption profiles, and to illustrate the effect of various model parameters on plasma drug concentration versus time profiles and bioavailability. METHODS: A discontinuous oral absorption model was used to fit ranitidine and cimetidine serum concentrations following oral and intravenous administration. The model was also used to simulate bioavailability and plasma concentrations versus time profiles for various parameter values. RESULTS: Serum concentrations following administration of ranitidine and cimetidine were well described by the model, and parameter estimates obtained were in agreement with literature values. Simulations demonstrate the effects of various absorption parameters and gastroin-testinal tract transit parameters on bioavailability and plasma concentration profiles. CONCLUSIONS: This discontinuous oral absorption pharmacokinetic model can be a useful tool in characterizing absorption phases, disposition, and bioavailability of drugs exhibiting two absorption peaks following oral administration.

Administration, Oral↗
PubMed1998

Intestinal absorption of nutrients is not influenced by soy fiber and does not differ between oligomeric and polymeric enteral diets.

Enteric feeding is often associated with diarrhea. To avoid this side effect, isoosmotic and fiber-supplemented enteral diets are recommended. The aims of this study were to determine whether supplementing enteral diets with soy fiber influences nutrient absorption and whether in enteric feeding absorption of nutrients and water fluxes differ between hyperosmotic oligomeric and isoosmotic polymeric diets. In mini pigs intestinal absorption and water fluxes were measured by perfusing a 150-cm length of jejunum. Six noncommercial iso- and hyperosmotic oligomeric and polymeric diets and six commercial polymeric diets, either fiber-free or supplemented with soy fiber, were used. Pancreatic enzymes were infused concomitantly with the polymeric diets. The absorption of nutrients and energy did not differ between oligomeric and polymeric diets. Oligomeric diets of high energy density produced a pronounced secretion of water. Despite lower initial osmolality, polymeric diets produced a similar secretion of water due to rapid pancreatic hydrolysis. Supplementing diets with largely insoluble soy fiber increased viscosity only between 4.6 and 14.5 mPa x sec. Soy fiber did not influence absorption of nutrients and energy and had also no effects on luminal transit and flow rate. The lack of effects was not due to dilution of chyme by intestinal secretion of water because no differences existed between isoosmotic and hyperosmotic oligomeric diets. In conclusion, supplementing enteral diets with soy fiber does not impair the absorption of nutrients. Enteric feeding with isoosmotic polymeric diets provides no advantage compared with hyperosmotic oligomeric diets with respect to absorption of nutrients and secretion of water.

Animals↗
PubMed1998

Relationships between gastric emptying and intestinal absorption of nutrients and energy in mini pigs.

Little is known about the relationship between gastric emptying of nutrients regulated by feedback mechanisms and the absorptive capacity of the gut. Therefore, we wanted to elucidate these interrelationships. A 150-cm jejunal segment was perfused (1-8 kcal/min) with three different nutrient solutions (either 60% of energy as carbohydrate, or 60% as protein, or 33.3% of each nutrient). In separate experiments, gastric emptying was measured after administration of three different meals with the same nutrient composition as the perfusion solutions. The jejunal absorption of carbohydrate, protein, fat, and energy demonstrated saturation kinetics. The kinetics differed among the three nutrients; carbohydrates were absorbed at higher rates than fat and protein. Interactions among the nutrients altered the kinetics providing a constant absorption of energy. After meals, the stomach emptied equal amounts of energy despite large variations in meal composition. The available intestinal absorptive capacity for protein was utilized by 96%, whereas that for carbohydrate, fat and energy were utilized only by 46-62%. Besides reserves in the absorptive capacity, the intestine provided reserves in total length available for absorption. The results indicate a close relationship between the energy-dependent absorption of nutrients and the energy-dependent feedback inhibition of gastric emptying.

Animals↗
PubMed1999

Drug liposome partitioning as a tool for the prediction of human passive intestinal absorption.

PURPOSE: Appropriate physicochemical parameters are desired for the prediction of passive intestinal drug absorption during lead compound selection and drug development. METHODS: Liposome distribution coefficients measured titrimetrically and solubility data at pH 6.8 were used to characterize 21 structurally diverse ionizable drugs covering a range from <5% to almost complete absorption. RESULTS: A sigmoidal relationship was found between the percentage of human passive intestinal absorption and a new absorption potential parameter calculated from liposome distribution data and the solubility-dose ratio. In contrast, the human absorption data did not correlate with an octanol-based absorption potential or partitioning data alone. Poor correlations were found between liposome and octanol partitioning of ionic species or nonionic bases indicating the profound differences of the partitioning systems. CONCLUSIONS: Liposome distribution coefficients of ionizable drugs derived by a pH-metric titration were successfully used to calculate a parameter that correlates with the percentage of passive intestinal absorption in humans. Profound differences between liposome and octanol partitioning were found for a highly diverse set of species. This titration technique may serve to generate liposome partitioning data for the selection and optimization of lead compounds and in drug development.

Humans↗
PubMed1994

Modeling of the saturable time-constrained amoxicillin absorption in humans.

Amoxicillin pharmacokinetics was modeled using a two-compartment disposition model and a saturable time-constrained absorption model with a storage compartment. The absorption model parameters estimated by the nonlinear regression are: a rate constant of the systemic input, ksys, (median: 1.31 h-1, range: 0.79-7.01 h-1), a maximal absorption rate, Vmax (median: 1407 mg/h, range: 703-4181 mg/h), an account corresponding to the half maximal rate, Kma, (median: 1077 mg, range: 235-4376 mg), time of the absorption cessation, Tabs, (median: 1.72 h, range: 0.82-4.53 h) and absorption lag time. Tlag, (median: 0.085 h, range: 0-0.123 h). It was shown, that the first-order absorption parallel to the saturable process is negligible in the dose range studied. The model described well the dependence of areas under concentration-time curves on the dose determined in several earlier studies. It was used also to predict the fraction of the amoxicillin dose absorbed for different doses. Simulations performed over a wide dose range (50-10000 mg) demonstrated that the fraction absorbed decreases nonlinearly from 90% at 50 mg to 22% at 10000 mg and strongly depends on the duration of the absorption period.

Absorption↗
PubMed1994

Intestinal absorption of (-)-carbovir in the rat.

(-)-Carbovir (CBV) is a carbocyclic nucleoside analogue with in vitro activity against the human immunodeficiency virus. The sites and mechanism of absorption of (-)-CBV from the rat small intestine were studied in the anesthetized male Sprague-Dawley rat. (-)-CBV was perfused through either duodenal, jejunal, or ileal segments at three concentration levels ranging from 1 to 500 micrograms/mL. The fraction remaining to be absorbed at steady-state and the absorptive clearance were calculated for each experiment. The effect of solvent drag on the absorptive clearance was also investigated. Two-way ANOVA for the absorptive clearance per unit length was not significant for either (-)-CBV concentration or site of perfusion. The fraction remaining to be absorbed at steady-state was found to be 0.804 +/- 0.091 (n = 30). A strong correlation was found between the absorptive clearance and the net water absorptive flux. The mechanism of (-)-CBV absorption across the rat small intestine apparently consists of both passive diffusion and convection.

Analysis of Variance↗
PubMed1999

An integrated model for determining causes of poor oral drug absorption.

PURPOSE: To develop an integrated absorption model for estimating the fraction of dose absorbed and determining the causes of poor oral drug absorption. METHODS: Both analytical and numerical methods were used to estimate the fraction of dose absorbed. RESULTS: An integrated absorption model was developed by considering transit flow, dissolution, and permeation processes, simultaneously. A framework was proposed to determine permeability-, dissolution-, and solubility-limited absorption. Digoxin, griseofulvin, and panadiplon were employed to illustrate the applications of the integrated model in identifying the causes of poor absorption and guiding formulation development. CONCLUSIONS: The integrated absorption model was successfully applied to digoxin, griseofulvin, and panadiplon to estimate the fraction dose absorbed and to roughly determine the causes of poor oral drug absorption.

Administration, Oral↗
PubMed1994

Renin inhibitor: relationship between molecular structure and oral absorption.

Common problems in developing renin inhibitors are low solubility, insufficient oral absorption, and fast hepatic clearance. We focused on the molecular structure of renin inhibitors to overcome these problems. Cyclodextrins (CD) improved the low solubility of renin inhibitors, with beta-CD showing the best ability to dissolve renin inhibitors. The intestinal absorption of renin inhibitors varied with both their solubility and molecular structure. Coadministration of beta-CD improved the intestinal absorption of some renin inhibitors with low solubility as measured by transport into the mesenteric vein in the absorption experiment using the rat intestinal loop. Substitutions at both the N and C terminals was essential for absorption from the small intestine. A naphthyl group at the N-terminal further improved intestinal absorption. A carrier system appeared to be involved in the intestinal absorption of some renin inhibitors. N-methylation at the amide bond of thiazolylalanine suppressed the high hepatic clearance of one of the test compounds 18 which was well absorbed from the small intestine and it improved its oral bioavailability.

Animals↗
PubMed1999

Influence of cholestasis on absorption of ursodeoxycholic acid.

Ursodeoxycholic acid (UDCA) has beneficial effects in cholestatic liver diseases. Absorption of UDCA is slow and incomplete. In the present study the effect of cholestasis on absorption was evaluated in 10 patients with pancreatic carcinoma and extrahepatic biliary drainage. At days 3 and 10 after insertion of the biliary drain, all patients received 750 mg UDCA in three divided doses. On both occasions intestinal absorption of UDCA was determined to evaluate the influence of cholestasis. Serum bilirubin was used as indicator of cholestasis. Biliary output of UDCA served as measure of absorption and was determined by gas-liquid chromatography. At days 4 and 11 bile consisted of less than 2% of UDCA, indicating that UDCA excretion was complete within 24 hr and no accumulation of UDCA had occurred. After insertion of the drain, serum bilirubin decreased from 12.2 +/- 2.4 mg/dl at day 3 to 5.4 +/- 0.9 mg/dl at day 10. Biliary secretion of bile acids increased from 2.0 +/- 0.3 to 3.1 +/- 0.4 mmol/day, whereas percentage of ursodeoxycholic acid in bile did not significantly increase (41.1% vs 42.1%). Absorption of UDCA increased from 39.8 +/- 5.0% to 61.1 +/- 6.2% of the administered dose, indicating an improvement of the absorption rate after decrease of cholestasis by 53.65% (P < 0.05). In conclusion, in severe cholestasis absorption of orally administered UDCA is markedly reduced. This may have implications in the treatment of patients with cholestatic disease.

Administration, Oral↗
PubMed2005

Measurements of zinc absorption: application and interpretation in research designed to improve human zinc nutriture.

The focus of this paper is on the application of measurements of zinc absorption in human research, especially studies designed to assess the efficacy of intervention strategies to prevent and manage zinc deficiency in populations. Emphasis is given to the measurement of quantities of zinc absorbed rather than restricting investigations to measurements of fractional absorption of zinc. This is especially important when determining absorption of zinc from the diet, whether it be the habitual diet or an intervention diet under evaluation. Moreover, measurements should encompass all meals for a minimum of one day with the exception of some pilot studies. Zinc absorption is primarily via an active saturable transport process into the enterocytes of the proximal small intestine. The relationship between quantity of zinc absorbed and the quantity ingested is best characterized by saturable binding models. When applied to human studies that have sufficient data to examine dose-response relationships, efficiency of absorption is high until approximately 50-60% maximal absorption is achieved, even with moderate phytate intakes. This also coincides approximately with the quantity of absorbed zinc necessary to meet physiologic requirements. Efficiency of absorption with intakes that exceed this level is low or very low. These observations have important practical implications for the design and interpretation of intervention studies to prevent zinc deficiency. They also suggest the potential utility of measurements of the quantity of zinc absorbed when evaluating the zinc status of populations.

Biological Availability↗
PubMed1977

Effect of glycylglycine on absorption from human jejunum of an amino acid mixture simulating casein and a partial enzymic hydrolysate of casein containing small peptides.

1. A jejunal perfusion technique has been used in normal volunteer subjects to study jejunal absorption of amino acid residues from a partial enzymic hydrolysate of casein in which about 50% of the amino acids existed as small peptides, and also from an equivalent mixture of free amino acids. 2. The effect of a high concentration of the dipeptide glycylglycine on the absorption of amino acid residues from these preparations was studied to quantify the importance of mucosal uptake of intact peptides during absorption of the partial hydrolysate of casein. 3. The results were unexpected. Glycylglycine significantly inhibited absorption of several amino acid residues (aspartic acid + asparagine, serine, glutamic acid + glutamine, proline, alanine, phenylalanine, threonine and isoleucine) from the free amino acid mixture, whereas it significantly inhibited the absorption of only two (serine, glutamin acid + glutamine) from the peptide-containing partial casein hydrolysate. 4. The effect of glycylglycine on absorption of amino acids from the mixture of free amino acids was apparently due to inhibition of amino acid uptake by free glycine liberated from the dipeptide during perfusion. The reason for the failure of glycylglycine to cause extensive inhibition of absorption from the partial hydrolysate is not clear. It may be due to glycylglycine being only a weak inhibitor of peptide uptake, but the possibility that some peptides are taken up by a system unavailable to glycylglycine has to be considered.

Adult↗
PubMed1980

The reproducibility of double-isotope deconvolution measurements of intestinal calcium absorption.

1. Radiocalcium absorption was measured in duplicate in 10 subjects by the double-isotope method, with calcium as the oral carrier (2.5 mmol). Analysis of variance gave 95% confidence limits for a single measurement of fractional absorption and maximum absorption rate in a given individual of +/- 16.5% of administered dose and +/- 18.2% of dose/h respectively. 2. The size of these within individual variations suggests that alterations in the rate of calcium absorption may contribute to the week-to-week stabilization of some other controlled variable, such as plasma concentration of calcium. 3. In six of the subjects, calcium absorption was also measured with calcium loads at concentrations of 0.5, 5.0 and 20 mmol. Significant falls in fractional absorption, maximum absorption rate and mean transfer rate occurred as the load increased, together with a rise in mean transit time. Although between-individual differences at a given load were considerable, given a single-test result with a known carrier load, it is possible to predict quite accurately the results which would be obtained if a different carrier load were to be given.

Analysis of Variance↗
PubMed1981

Comparison of radioisotope methods for the measurement of phosphate absorption in normal subjects and in patients with chronic renal failure.

1. Intestinal phosphate absorption was measured in normal subjects, in patients with chronic renal failure, and in post-transplant patients, by a double isotope technique involving oral administration of 32P and simultaneous intravenous injection of 33P with subsequent deconvolution analysis. 2. By this technique intestinal phosphate absorption has been shown to have two components: an initial rapid phase, which is completed by 3 h, and a slower more prolonged phase, which continues beyond 7 1/2 h. 3. Phosphate malabsorption has been demonstrated in chronic renal failure and transplant patients, which is accounted for by impairment of the initial rapid phase of absorption. 4. Results obtained by deconvolution analysis have been compared with other estimates of phosphate absorption obtained from analysis of 32P radioactivity curves alone. 5. The fractional hourly rate of absorption and the plasma 32P radioactivity at 60 min corrected for extracellular fluid volume provided the best approximations to the result obtained by deconvolution analysis, with respect to both the maximal rate of phosphate absorption and cumulative percentage phosphate absorption.

Administration, Oral↗
PubMed2002

Validation of the ethanol breath test and on-table weighing to measure irrigating fluid absorption during transurethral prostatectomy.

OBJECTIVE: To determine the agreement between on-table weighing and the ethanol breath test in measuring the fluid absorption of patients during transurethral prostatectomy (TURP), and to assess the practicality of on-table weighing in the clinical setting. PATIENTS AND METHODS: The absorption of irrigating fluid by the patient during TURP can lead to adverse sequelae, including cardiac stress. Despite modern techniques irrigant may still be absorbed and therefore methods to detect absorption are important. Most methods are impractical or inaccurate, but the expired ethanol technique and continuous on-table weighing are more promising. TURP was undertaken in 44 men (mean age 71 years) using continuous flow 1.5% glycine/1% ethanol as the irrigating solution. Intraoperative irrigant absorption was calculated by the ethanol breath test, using published formulae. Absorption measured by the weighing machine was calculated as (weight gain + blood loss - fluid given), and blood loss by the Hemocue method. RESULTS: The mean (sd) resected weight was 23 (14) g at a mean resection rate of 0.74 g/min. The mean (range) absorption using the balance was 456 (- 343 to 2486) mL, and using the ethanol breath test was 435 (44-2750) mL, with the mean of the differences being - 17 mL, with a 95% confidence interval (CI) of - 81 to -40, the 95% limits of agreement being - 389 to 356 mL (95% CI - 458 to - 337 and 297 to 418 mL). CONCLUSIONS: Both methods are comparable and measure irrigating fluid absorption to levels of accuracy that are useful clinically. Either method could (and should) be used in routine practice.

Absorption↗
PubMed1999

Hyaluronan decreases peritoneal fluid absorption: effect of molecular weight and concentration of hyaluronan.

BACKGROUND: We have recently shown that the addition of hyaluronan to peritoneal dialysis solution could decrease the peritoneal fluid absorption rate, possibly through decreasing peritoneal tissue hydraulic conductivity. The physical-chemical properties of hyaluronan were found to be both molecular weight and concentration dependent. In this study, we investigated the effects of different molecular weight as well as different concentrations of hyaluronan on the peritoneal fluid kinetics. METHODS: A four-hour dwell study was performed in 48 male Sprague-Dawley rats (6 rats in each group) with 131I albumin (RISA) as an intraperitoneal volume marker. Each rat was intraperitoneally injected with 25 ml of 1.36% glucose dialysate alone (control) or with 0.01% hyaluronan (HA) with different molecular weights [85,000 (HA85K group), 280,000 (HA280K group), 500,000 (HA500K group), and 4,000,000 (HA4M group) molecular wt] or with a different concentrations of hyaluronan [(molecular wt 500,000); 0.01% (0.01% HA group), 0.05% (0.05% HA group), 0.1% (0.1% HA group), and 0.5% (0.5% HA group) hyaluronan]. RESULTS: The peritoneal fluid absorption rate (as assessed by the RISA elimination rate, KE) was significantly decreased in the HA500K and H4M groups as well as in all the different concentration groups (with molecular wt 500,000) as compared with the control group, resulting in significantly higher net fluid removal in these groups (except for the H4M group) as compared with the control group. In the 0.5% HA group (but not in the other hyaluronan groups), the direct lymphatic absorption (KEB) was also significantly decreased. The transcapillary ultrafiltration rate (Qu) was significantly lower in the HA4M group as compared with the control group but significantly higher in the 0.05% HA (and tended to be higher in the 0.1% HA group) as compared with the other groups. No difference in Qu was found between the 0.5% HA group as compared with the control group, despite a more marked decrease in KE in this group as compared with the H4M group. There were no significant differences in KE, Qu, and net fluid removal between the HA85K and HA280K groups and the control group. CONCLUSIONS: Our results suggest that (a) the addition of hyaluronan to dialysate could decrease peritoneal fluid absorption and thus increase the net ultrafiltration; this effect appears to be both size dependent and concentration dependent. (b) High molecular weight fraction of hyaluronan may also decrease the transcapillary Qu by decreasing tissue hydraulic conductivity. (c) A higher concentration of hyaluronan in dialysate resulted in a more marked decrease in peritoneal fluid absorption (absorption to peritoneal tissues as well as direct lymphatic absorption), possibly through both decreasing tissue hydraulic conductivity and increasing fluid viscosity. (d) Decreasing tissue hydraulic conductivity by adding a high concentration of hyaluronan to dialysate does not decrease the transcapillary ultrafiltration, possibly because the osmotic effect of hyaluronan may counterbalance the decrease in transcapillary ultrafiltration because of the decrease in tissue hydraulic conductivity.

Absorption↗
PubMed2000

No difference in intestinal strontium absorption after oral or IV calcitriol in children with secondary hyperparathyroidism. The European Study Group on Vitamin D in Children with Renal Failure.

BACKGROUND: Oral and intravenous calcitriol bolus therapy are both recommended for the treatment of secondary hyperparathyroidism, but it has been claimed that the latter is less likely to induce absorptive hypercalcemia. The present study was undertaken to verify whether intravenous calcitriol actually stimulates intestinal calcium absorption less than oral calcitriol and whether it is superior in suppressing parathyroid hormone (PTH) secretion. METHODS: Twenty children (16 males, age range of 5.1 to 16.9 years, mean creatinine clearance 21.9 +/- 11.5 mL/min/1.73 m2, range of 7.4 to 52.7) with chronic renal failure (CRF) and secondary hyperparathyroidism [median intact PTH (iPTH), 327 pg/mL; range 143 to 1323] received two single calcitriol boli (1.5 mg/m2 body surface area) orally and intravenously using a randomized crossover design. iPTH and 1,25(OH)2D3 levels were measured over 72 hours, and intestinal calcium absorption was measured 24 hours after the calcitriol bolus using stable strontium (Sr) as a surrogate marker. Baseline control values for Sr absorption were obtained in a separate group of children with CRF of similar severity. RESULTS: The peak serum level of 1,25(OH)2D3 and area under the curve baseline to 72 hours (AUC0-72h) were significantly higher after intravenous (IV) calcitriol (AUC0-72h oral, 1399 +/- 979 pg/mL. hour vs. IV 2793 +/- 1102 pg/mL. hour, P < 0.01), but the mean intestinal Sr absorption was not different [SrAUC0-240min during the 4 hours after Sr administration 2867 +/- 1101 FAD% (fraction of the absorbed dose) vs. 3117 +/- 1581 FAD% with oral and IV calcitriol, respectively]. The calcitriol-stimulated Sr absorption was more then 30% higher compared with control values (2165 +/- 176 FAD%). A significant decrease in plasma iPTH was noted 12 hours after the administration of the calcitriol bolus, which was maintained for up to 72 hours without any differences regarding the two routes of administration. CONCLUSIONS: These results demonstrate that under acute conditions, intravenous and oral calcitriol boli equally stimulate calcium absorption and had a similar efficacy in suppressing PTH secretion.

Administration, Oral↗
PubMed1991

Digestion and absorption of polyunsaturated fatty acids.

Polyunsaturated fatty acids play an important part in the structure and function of cellular membranes and are precursors of lipid mediators which play a key role in cardiovascular and inflammatory diseases. Dietary sources of essential fatty acids are vegetable oils for either linoleic or alpha-linolenic acids, and sea fish oils for eicosapentaenoic and docosahexaenoic acids. Because of the specificity of the pancreatic lipid hydrolases, triglyceride fatty acid distribution is an essential parameter in the digestibility of fats. The efficiency of the intestinal uptake depends on the hydrolysis and especially on their micellarization. n-3 polyunsaturated fatty acid ethyl ester digestion is recognized to be impaired, but n-3 polyunsaturated fatty acid triglyceride hydrolysis remains a controversial point, and to some authors explains differences observed between vegetable and fish oil absorption. So additional studies are required to investigate this intestinal step. In enterocytes, morphological and biochemical absorption processes involve reesterification of long-chain fatty acids and lipoprotein formation. At this level, specific affinity of I- and L-FABPc (cytosolic fatty acid binding proteins) to polyunsaturated fatty acids requires further investigation. A better understanding of the role of these FABPc might bring to light the esterification step, particularly the integration of polyunsaturated fatty acids into phospholipids. With reference to differences published between fish and vegetable oil absorption, longer-term absorption studies appear essential to some authors. Polyunsaturated fatty acid absorption is thought to be not very dissimilar to that of long-chain mono-unsaturated fatty acid absorption. However, several digestion and absorption specific steps are worth studying with reference to the crucial role of polyunsaturated fatty acids in the organism, and for example adaptation of possible dietary supplements.

Dietary Fats, Unsaturated↗
PubMed2002

Evaluation of intestinal iron absorption by indirect methods in patients on hemodialysis receiving oral iron and recombinant human erythropoietin.

Intestinal iron absorption was evaluated in 40 patients on hemodialysis therapy treated over 4 months with 105 mg/d of oral iron and recombinant human erythropoietin (rHuEPO). The effect of iron stores, erythropoietic activity (EA), and route of rHuEPO administration on absorption was evaluated. Iron was administered after basal determinations had been made and was stopped 15 days before obtaining the final determinations. Intestinal iron absorption was calculated by summing the increase in hemoglobin (Hb) iron (iron used for the synthesis of new Hb) and variations in estimated tissue iron reserves (reserves at the end of the study minus basal reserves). Markers of EA included soluble transferrin receptors (sTfRs) and erythron transferrin uptake (ETU). Iron losses caused by dialysis or normal obligatory iron losses were not measured. Hb levels increased from 8.38 +/- 1.4 to 10.75 +/- 1.5 g/dL (P < 0.05). sTfR levels reached their maximum value at 45 days (3.22 +/- 0.84 mg/mL; P < 0.05), and ETU increased from 40 +/- 26 to 61 +/- 39 micromol/L whole blood/d (P = 0.007). Intestinal iron absorption was 238 mg (interquartile range [Q75 to Q25], 255) at 2 months and 348 mg (Q75 to Q25, 475) at 4 months (P =0.02) and correlated positively with hematocrit at the end of the study (r = 0.826; P = 0.0001). No relationship between iron absorption and basal serum ferritin level or EA markers was observed. Intestinal iron absorption was similar regardless of the route of rHuEPO administration. In conclusion, intestinal iron absorption from medicinal iron covers erythropoietic requirements and allows Hb levels to increase significantly. It is proportional to the degree of efficient erythropoiesis reached and independent of tissue iron stores present before treatment, markers of EA, and rHuEPO administration route.

Administration, Oral↗