Intravenous Calcitriol Treatment Research Articles

Intravenous calcitriol treatment benefits the homeostasis of CD4+ T cells and attenuates kidney injury in obese mice complicated with polymicrobial sepsis

ObjectivesSepsis is a lethal clinical condition with dysregulated cluster of differentiation (CD) 4+ T cells that leads to inflammation and multiorgan injury. Low vitamin D levels are commonly seen in patients with sepsis. Obesity is a state with oxidative stress and chronic inflammation. Both obesity and low vitamin D levels are associated with adverse outcomes in patients with sepsis. This study investigated the effects of calcitriol on CD4+ T-cell polarization and kidney injury during sepsis. MethodsMice were fed a high-fat diet to induce obesity. One group of obese mice served as the control group and in the other two groups (SS and SD) were performed cecal ligation and puncture (CLP) to induce sepsis. Mice in the SS group were injected with saline and those in the SD group with calcitriol 1 h after CLP via tail vein. Mice with sepsis were euthanized at 12 h and 24 h after CLP, respectively. ResultsSepsis led to a decrease in circulating CD4+ T-cell percentage, and T helper (Th) 2, Th17, and regulatory T (Treg) cell percentages were upregulated. Compared with the SS group, the SD group maintained blood CD4+ T-cell levels, and were reduced the Th2 and Th17 percentages as well as the Th17:Treg ratio. Also, plasma levels of cathelicidin increased, but inflammatory chemokines and kidney injury markers were reduced. Higher arginase-1 and lower inducible nitric oxide synthase expressions in the SD group indicated M1 macrophage polarized toward the M2 type. ConclusionsThese findings suggest that intravenous calcitriol administration after sepsis modulates the homeostasis of CD4+ T-cell subpopulations associated with alleviating sepsis-induced kidney injury in obese mice.

Intravenous calcitriol administration modulates mesenteric lymph node CD4+ T-cell polarization and attenuates intestinal inflammation in obese mice complicated with polymicrobial sepsis.

Sepsis is a lethal syndrome with T-cell dysregulation, imbalanced inflammatory reactions, and gastrointestinal dysfunction. Obesity coexistent with sepsis can cause more-deleterious disease outcomes. Vitamin D is a nutrient with immunomodulatory ability and helps maintain intestinal homeostasis. This study investigated treatment with calcitriol on mesenteric lymph node (MLN) CD4+ T-cell polarization and intestinal injury in obese mice with sepsis. Mice received a high-fat diet for 10 weeks; then, mice were separated into an obese control group without sepsis and sepsis groups that underwent cecal ligation and puncture (CLP). Septic mice were subdivided into a group that was injected with saline (SS group) or a group that was injected with calcitriol (SD group) via a tail vein 1 h after CLP. Obese mice with sepsis were euthanized at 12 or 24 h post CLP. Sepsis resulted in increased percentages of type 2 T helper (Th2), Th17, and regulatory T (Treg) cells in MLNs. Also, inflammation-associated genes were upregulated and tight junction genes downregulated in the intestines after CLP. Compared with the SS group, the SD group exhibited reduced Th2, Th17, and Treg percentages in MLNs. Also, intestinal inflammatory chemokine expressions were reduced, whereas MUC2, ZO-1, and occludin had increased after CLP. Lower inflammatory cytokine levels in peritoneal lavage fluid in the ileum were also noted in the SD group. Intravenous calcitriol treatment after sepsis can elicit more-balanced CD4 T-cell subsets in lymph nodes near the intestines and alleviate intestinal inflammation and injury in obese mice complicated with sepsis.

Vitamin D Receptor Activator Reduces Oxidative Stress in Hemodialysis Patients With Secondary Hyperparathyroidism

Treatment with a vitamin D receptor activator (VDRA) has survival benefits probably related to its effects beyond the traditional role in mineral metabolism. We hypothesized that VDRA reduces oxidative stress in hemodialysis (HD) patients. To test this hypothesis, we investigated the effect of VDRA on the oxidative status of albumin in HD patients with secondary hyperparathyroidism. Eleven HD patients with secondary hyperparathyroidism were treated with calcitriol at an intravenous dose of 1.5 µg/week for four weeks. Serum intact parathyroid hormone, calcium and phosphorus were monitored and we measured the amount of oxidized albumin and albumin hydroperoxides form before and after calcitriol treatment. The ratio of oxidized to un-oxidized albumin was determined as a representative marker of oxidative stress. The radical scavenging activity of albumin was also evaluated. After four weeks of calcitriol therapy, there were no significant changes in serum intact parathyroid hormone, calcium, or phosphorus levels; however, the ratio of oxidized to un-oxidized albumin was markedly decreased and serum thiol content was significantly increased after calcitriol treatment. Furthermore, the radical scavenging activity of albumin was greater after calcitriol treatment compared with that of untreated albumin. Our data suggest that intravenous calcitriol treatment reduces oxidative stress and strengthens antioxidant defenses by inhibiting albumin oxidation in HD patients with secondary hyperparathyroidism.

Comparison of oral falecalcitriol and intravenous calcitriol in hemodialysis patients with secondary hyperparathyroidism: a randomized, crossover trial

Falecalcitriol is a novel vitamin D analog, which has a greater potential to suppress parathyroid hormone (PTH) and a longer half-life. There are few studies to compare clinical effects of oral falecalcitriol treatment with those of intravenous calcitriol treatment. Twenty-one patients with moderate to severe SHPT were included in a random 2 x 2 crossover trial with the two vitamin D analogs (12 weeks for each treatment). The primary endpoint measure was a decrease in serum intact PTH (iPTH) level, and the secondary outcome measures included changes in serum calcium (Ca), phosphate (P), and metabolic bone marker levels. Both treatments decreased iPTH and whole PTH (wPTH) levels by similar degrees (iPTH, -200.1 +/- 107.0 with falecalcitriol vs. -200.8 +/- 114.9 pg/ml with calcitriol, p = 0.9895; wPTH, -137.1 +/- 73.1 with falecalcitriol vs. -120.4 +/- 81.1 pg/ml with calcitriol, p = 0.5603). Serum Ca, P, and Ca x P product levels at the end of each treatment were comparable and the frequencies of hypercalcemia and hyperphosphatemia were also similar during each treatment period. Although intravenous calcitriol treatment significantly changed intact osteocalcin and cross-linked N-telopeptide of type I collagen after 12 weeks, oral falecalcitriol treatment did not change any bone metabolic marker level. The present study showed that oral falecalcitriol treatment is effective for PTH suppression, and Ca and P metabolism in hemodialysis patients with moderate to severe SHPT, as well as intravenous calcitriol administration.

Influence of parathyroid mass on the regulation of PTH secretion

In advanced uremia, parathyroid hormone (PTH) levels should be controlled at a moderately elevated level in order to promote normal bone turnover. As such, a certain degree of parathyroid gland (PG) hyperplasia has to be accepted. No convincing evidence of apoptosis or of involution of PG hyperplasia exists. However, even considerable parathyroid hyperplasia can be controlled when the functional demand for increased PTH levels is abolished. When 20 isogenic PG were implanted into one parathyroidectomized (PTX) rat normalization of Ca(2+) and PTH levels and normal suppressibility of PTH secretion by high Ca(2+) was obtained. Similarly, normal levels of Ca(2+) and PTH and suppressibility of PTH secretion were obtained when Eight isogenic PG from uremic rats were implanted into normal rats or when long-term uremia and severe secondary hyperparathyroidism (sec. HPT) was reversed by an isogenic kidney transplantation. Normalization of PTH levels after experimental kidney transplantation took place despite a persistent decrease of vitamin D receptor (VDR) mRNA and calcium sensing receptor (CaR) mRNA in PG. Thus, in experimental models PTH levels are determined by the functional demand and not by parathyroid mass, per se. When non-suppressible sec. HPT is present in patients referred to PTX, nodular hyperplasia with differences in gene expression between different nodules has been observed in most cases. An altered expression of some autocrine/paracrine factors has been demonstrated in the nodules. Enhanced expression of PTH-related peptide (PTHrP) has been demonstrated in PG from patients with severe secondary HPT. PTHrP has been shown to stimulate PTH secretion in vivo and in vitro. PTH/PTHrP receptor was demonstrated in the parathyroids. The low Ca(2+) stimulated PTH secretion was enhanced by 300% by PTHrP 1-40. The altered quality of the parathyroid mass and not only the increased parathyroid mass, per se, might be responsible for non-controllable hyperparathyroidism in uremia and after kidney transplantation.

Calcitriol Regresses Cardiac Hypertrophy and QT Dispersion in Secondary Hyperparathyroidism on Hemodialysis

Background: Sudden cardiac death is common in patients on hemodialysis (HD), and its rate is as high as 25% of all cardiac deaths associated with left ventricular hypertrophy (LVH) and secondary hyperparathyroidism. A prolonged QT interval on standard electrocardiography is related to an increase in sudden death in various patient groups. It is also well known that LVH has been noted in uremic patients with high parathyroid hormone levels. Methods: To evaluate the response of intravenous calcitriol treatment on the QT interval and LVH in HD patients with secondary hyperparathyroidism (intact parathyroid hormone, iPTH, >450 ng/ml), echocardiographic, electrocardiographic (ECG), and biochemical assessments were performed over a 15-week period in 25 HD patients before and after intravenous calcitriol treatment. We also evaluated 25 age-, sex-, HD duration-, and BMI-matched HD control patients with secondary hyperparathyroidism. Results: In patients receiving intravenous calcitriol, a significant reduction in iPTH levels (p < 0.05) and alkaline phosphatase levels (p < 0.01) was found without changes in values of serum calcium and ionized Ca²⁺, phosphorus, Na⁺, K⁺, Mg²⁺, hematocrit, blood pressure, or other hemodynamic changes. Echocardiograms showed significant decreases in the thickness of the interventricular septum (p < 0.05), left posterior wall thickness (p < 0.05), and left ventricle mass index (LVMi, p < 0.01). In addition, sequential ECG measurement in patients with calcitriol treatment showed significant reductions in QTc_max (QT_max interval corrected for heart rates, p < 0.01) and QTc dispersion (QT dispersion corrected for heart rates, p < 0.01). However, in the control patients, biochemical, hemodynamic, and ECG changes, as well as myocardial structural and functional changes were not seen. Multiple regression analysis in all patients indicated that iPTH and LVMi levels were independent predictors of QTc_max while the LVMi level was the only independent predictor of QTc dispersion (p < 0.05). Conclusions: Our study showed a significant correlation between LVMi and QT dispersion in HD patients with secondary hyperparathyroidism. Intravenous calcitriol treatment, to be used for the control of secondary hyperparathyroidism, was found to cause regression of myocardial hypertrophy and a reduction in the QTc interval and dispersion, without biochemical and hemodynamic changes. These findings suggest that an active vitamin D metabolite has a cardioprotective action in HD patients.

Comparative Effect of Oral Pulse and Intravenous Calcitriol Treatment in Hemodialysis Patients: The Effect on Serum IL-1 and IL-6 Levels and Bone Mineral Density

Introduction: Increased serum levels of bone-resorptive cytokines such as interleukin-1β (IL-1β) and interleukin-6 (IL-6) have been implicated for changes in bone remodeling in hemodialysis patients. In this prospective randomized study, we aimed to compare the effect of oral and intravenous (IV) pulse calcitriol on serum levels of IL-1β and IL-6. Patients and Methods: Twenty-eight hemodialysis patients were included and consecutively randomized to receive either oral (n = 14, M/F = 7/7, mean age 42 ± 15 years) or IV pulse (n = 14, M/F = 6/8, mean age 38 ± 14 years) calcitriol treatment. No difference was found between groups for age, sex distribution, primary renal disease, mean time on hemodialysis and baseline biochemical parameters including serum levels of IL-1β and IL-6. Results: The percent fall of intact parathyroid hormone (iPTH) was significantly less with oral compared to IV calcitriol between 0 and the 3rd month (32 ± 21 vs. 56 ± 28%, p = 0.03). However, the percent fall in iPTH at the 6th month of the therapy was not different in the oral group compared to the IV group (57 ± 22 vs. 73 ± 24%, p = 0.12). The increase in bone mineral densities was higher in the IV group than the oral group. Oral and IV calcitriol caused a significant fall in IL-1β (p = 0.02 and p = 0.03, respectively) and IL-6 levels (p = 0.02 and p < 0.001, respectively) at the 6th month of treatment. The percent fall in serum IL-6 levels at the 6th month was significantly greater in the IV compared to the oral group (61 ± 18 vs. 36 ± 33%, p = 0.04), while the percent changes in serum IL-1β levels were similar. Conclusion: IV calcitriol therapy has a greater suppression of PTH at the 3rd month of the therapy. Despite no difference in serum PTH levels at the 6th month, IV therapy has a greater increase in bone mineral densities and a greater decrease in serum IL-6 levels. These findings suggest IV calcitriol treatment has a superior effect on bone remodeling by influencing the levels of bone-resorptive cytokines as compared to the oral therapy group, beyond its suppressive effect on iPTH.

Subtotal parathyroidectomy in renal failure: still needed after all these years.

There are scant data on the frequency of parathyroidectomy (PTX) for end-stage renal disease (ESRD). Medical therapy for ESRD and secondary hyperparathyroidism has evolved to include better dialytic urea removal and the use of calcitriol. The aim of this study was to determine whether medical therapy has changed the frequency or indications for PTX in the management of renal failure. Hospital and clinic records were analyzed to gather information on all patients undergoing PTX for secondary hyperparathyroidism (2HPT) (n = 48) and tertiary hyperparathyroidism (3HPT) (n = 26) from 1986 through 1998 at our institution. Prospective computer databases were queried for information concerning both chronic dialysis and renal transplant patients at our center. The patients were divided based on date of operation before or after 1991, a divider that separated the patients into groups before or after the widespread adoption of intravenous calcitriol treatment during hemodialysis at our institution. Over the 12 year period, the proportion of our chronic dialysis patients undergoing PTX did not change significantly, ranging from 0% to 2.5% per year. Comparing all patients undergoing PTX for 2HPT during 1986-1991 versus 1992-1998, there was no significant difference in time on dialysis [7.0 +/- 4.2 (n = 11) vs. 7.5 +/- 4.6 (n = 36) years, mean +/- SD]. The later group had higher intact parathyroid hormone (iPTH) levels [765 +/- 415 (n = 6) vs. 1377 +/- 636 (n = 28) pg/ml; p = 0.03], lower serum calcium [11.2 +/- 1.0 (n = 12) vs. 9.9 +/- 1.5 (n = 34) mg/dl; p = 0.006], and higher serum phosphate [5.7 +/- 1.6 (n = 12) vs. 7.2 +/- 2.3 (n = 31) mg/dl; p = 0.042]. Among the population of patients with transplants undergoing PTX for 3HPT, the average percent per year undergoing PTX ranged from 0% to 4.2% and did not change during the study period. Comparing the 1986-1991 group to the 1992-1998 group, the time from transplantation to PTX did not change during the study period (3.3 +/- 2.3 vs. 2.9 +/- 3.0 years; p = 0.391), and there were no significant differences between preoperative calcium levels or iPTH levels. Despite advances in dialysis technique and pharmacologic therapy, there has been no change in the proportion of dialysis patients requiring PTX for 2HPT or 3HPT. There was also no change in the time on dialysis for patients with 2HPT or the time from transplant to PTX for patients with 3HPT. Analysis of preoperative biochemical markers as evidence of disease severity suggests there was no change in indications for PTX during our study. From this information we conclude that parathyroid pathophysiology is incompletely understood and medical therapy is not optimal, resulting in a continuing need for PTX in some patients.

Calcitriol modulates in vivo and in vitro cytokine production: A role for intracellular calcium

Calcitriol modulates in vivoand in vitro cytokine production: A role for intracellular calcium. Background. Several immunomodulatory properties of calcitriol are currently known, however, only little information is available regarding the in vivo and in vitro effects of calcitriol on cytokine production in chronic renal failure. Methods. To study the in vitro effect of calcitriol on lipopolysaccharide (LPS)-induced cytokine production, peripheral blood mononuclear cells (PBMC, 2.5 ml/ml) from 12 chronic dialytic (HD), 15 undialyzed chronic renal failure (CRF) patients and 10 normal subjects (N) were incubated at 37 degrees for 12 hours with 100 ng of LPS (E. coli and P. maltofilia). Increasing doses of calcitriol from 10-10 to 10-9 M were added and cell associated TNF-alpha and IL-1beta were determined by immunoreactive tests after three freeze-thaw cycles. The intradialytic TNF-alpha and IL-1beta production were evaluated in vivo in 12 HD patients before and after three months of intravenous calcitriol treatment (6 microgram/week). Intracellular calcium [Ca++]i was determined on PBMC with a cytofluorimetric assay using FLUO-3 AM as the indicator. Results. In vitro, TNF-alpha increased from 3.6 +/- 1.9 pg/cell to 1797 +/- 337 in N, from 4.5 +/- 1.7 to 1724 +/- 232 in CRF and from 3.4 +/- 2.3 to 1244 +/- 553 in HD after the LPS stimulus. The production of TNF-alpha was inhibited by calcitriol in a dose-dependent manner [LPS + Vit.D3 100 ng, 2.9 +/- 2.1 in N, 3.7 +/- 1.9 in CRF and 3.4 +/- 1.7 in HD; LPS + Vit.D3 50 ng, 263 +/- 296 (N), 6.73 +/- 11 (CRF), 38 +/- 28 (HD); LPS + Vit.D3 25 ng = 873 +/- 583 (N), 325 +/- 483 (CRF), 588 +/- 507 (HD); LPS + Vit.D3 12.5 ng, 954 +/- 483 (N), 912 +/- 510 (CRF), 875 +/- 527 (HD)]. Comparable data were observed on IL-1beta production. In vivo, the intradialytic TNF-alpha increase (from 8.5 +/- 2.3 to 19 +/- 5.6 pg/2.5 x 106 cell) during hemodialysis was markedly reduced after calcitriol therapy (from 6.6 +/- 3.1 to 11 +/- 4.7). [Ca++]i decreased from 105 +/- 25 to 72 +/- 18 nM (P < 0.05) and a positive correlation between cytokine levels and [Ca++]i was found (r = 0.79; P < 0.001). Conclusions. The in vitro increase of cell-associated cytokine after LPS challenge was inhibited by calcitriol in a dose-dependent manner. These data suggest a possible in vivo modulatory effect of calcitriol therapy on cytokine production in hemodialysis.

Intravenous Calcitriol Improves Anaemia and Reduces the Need for Erythropoietin in Haemodialysis Patients

In cases with severe hyperparathyroidism, anaemia improves after parathyroidectomy. The objective of this study was to investigate the influence of treatment with intravenous calcitriol on anaemia in 28 haemodialysis patients. The patients showed moderate to severe hyperparathyroidism (mean parathyroid hormone level 811.6 ± 327 pg/ml) and were treated with calcitriol (2 µg i.v.) after haemodialysis. The follow-up period was 12 months. 21 out of the 28 patients had been receiving erythropoietin (EPO) prior to calcitriol administration; the remaining 7 did not receive EPO. 24 patients received oral or intravenous iron. The doses of EPO and iron were modified throughout the study period to maintain a haematocrit equal to or higher than 30% and ferritin levels above 150 ng/ml, respectively. EPO needs were evaluated according to the relation EPO dose/haematocrit. We found a significant rise in haematocrit and haemoglobin at 3 and 12 months on calcitriol therapy, with no modification of the EPO dose nor ferritin levels. This improvement in anaemia was observed both in those patients who received EPO initially (p < 0.01) and in those who did not (p < 0.05). Upon dividing the patients according to the response of hyperparathyroidism to the intravenous calcitriol treatment, we observed in the responding patients (n = 19) significant increases in haematocrit (from 31.7 ± 4.2 to 36.3 ± 4.9%) and haemoglobin (from 10.6 ± 1.5 to 12.2 ± 1.5 g/dl; p < 0.001) at 12 months on intravenous calcitriol therapy, while this was not true of the non-responding patients. The EPO needs diminished in the group of responding patients and increased in the non-responders, although these changes were not statistically significant. We found no direct correlation between the decrease of parathyroid hormone and EPO needs in the group of responding patients. However, an inverse correlation between parathyroid hormone levels and EPO needs (r = –0.799, p < 0.05) was seen in the group of non-responding patients. Treatment with intravenous calcitriol in patients on haemodialysis controls secondary hyperparathyroidism, improves anaemia, and decreases the need for EPO. Studies including a larger number of patients are necessary to clarify the mechanisms underlying the improvement of anaemia upon control of secondary hyperparathyroidism with intravenous calcitriol treatment and to confirm our findings.

Long-term effects of intravenous calcitriol therapy on the control of secondary hyperparathyroidism

Although high-dose intravenous calcitriol has been shown to be effective in suppressing parathyroid hormone (PTH) secretion in dialysis patients with secondary hyperparathyroidism, an increasing number of patients is refractory to treatment. Only a few studies have evaluated the factors that can predict a favorable response to calcitriol, but contrasting results have been reported. This study was performed to evaluate the effect of high-dose intravenous calcitriol on parathyroid function and to investigate the factors that can predict a favorable response to treatment. Thirty-five dialysis patients were selected for intravenous calcitriol treatment (2 μg after dialysis for 12 months) because of increased PTH levels (>325 pg/mL). Before starting the treatment, the set point of calcium and the PTH-ionized calcium (ICa) curve was evaluated in each patient by inducing hypocalcemia and, 1 week later, hypercalcemia to maximally stimulate or inhibit PTH secretion. Parathyroid glands were assessed by high-resolution color Doppler ultrasonography. Throughout the study, calcium carbonate or acetate dosage was modified to maintain serum phosphate less than 5.5 mg/dL. Hypercalcemia was managed by reducing dialysate calcium to 5 mg/dL and, if necessary, calcitriol dose. The therapeutic goal was to reduce PTH levels below 260 pg/mL while maintaining normocalcemia. The patients who achieved the therapeutic goal were considered responders. Taking the data from the 35 patients together, we observed a significant decrease ( P < 0.01) in alkaline phosphatase (from 252 ± 106 IU/L to 194 ± 81 IU/L) and PTH (from 578 ± 231 pg/mL to 408 ± 291 pg/mL), and a significant increase in serum ICa (from 5.1 ± 0.2 mg/dL to 5.3 ± 0.2 mg/dL; P < 0.001) after calcitriol therapy. PTH changes after therapy were not correlated to serum ICa changes, serum phosphate levels during treatment, and calcitriol dose. The response to therapy was heterogeneous because PTH levels markedly decreased over the treatment period in 18 responsive patients, whereas they increased or remained unchanged in 14 of 17 nonresponders. In three additional refractory patients, there was a decline in PTH of 20% to 35%, but this decline was associated with hypercalcemia. Pretreatment parathyroid gland size, serum ICa, PTH, maximal PTH induced by hypocalcemia, minimal PTH induced by hypercalcemia, the set point of ICa, and the ICa levels at which maximal PTH secretion and inhibition occurred were higher in the 17 refractory patients than in the 18 responsive patients. However, logistic regression analysis showed that among these parathyroid function parameters, the only significant predictors of a favorable response to calcitriol therapy were the parathyroid gland size and the set point of ICa. Throughout the study, serum phosphate and calcitriol dose were comparable in the two groups. In conclusion, the response to intravenous calcitriol therapy in dialysis patients with secondary hyperparathyroidism is heterogeneous, consisting of patients who are either responsive or refractory to treatment; refractoriness can be predicted by parathyroid volume and calcium set point.

Calcitriol administration in end-stage renal disease: intravenous or oral?

1,25-Dihydroxyvitamin D deficiency plays an important role in the pathogenesis of secondary hyperparathyroidism, and adequate replacement of this hormone is considered essential to normalize parathyroid gland function and restore bone homeostasis in patients with advanced renal failure. Although initial uncontrolled clinical trials suggested the superiority of intravenous calcitriol treatment, more recent controlled investigations show that different routes (oral versus intravenous), frequency (daily versus intermittent), and dosing (physiological versus pharmacological) of calcitriol administration are clinically equivalent. Overall, the response to calcitriol treatment depends more on the severity of secondary hyperparathyroidism and the presence of confounding variables, such as hyperphosphatemia and acquired abnormalities of parathyroid cell function, than the method of calcitriol administration.

Oral versus intravenous calcitriol

Deficiency of 1,25-dihydroxyvitamin D plays an important role in the pathogenesis of secondary hyperparathyroidism. Adequate replacement of this hormone is required to normalize parathyroid gland function and restore bone homeostasis in patients with advanced renal failure. Controversy exists regarding the best method of administering 1,25-dihydroxyvitamin D. Although initial, uncontrolled clinical trials suggested the superiority of intravenous calcitriol treatment, more recent controlled investigations have shown that different routes (oral versus intravenous), frequency (daily versus intermittent) and dosing (physiologic versus pharmacologic) of calcitriol administration are equivalent. Overall, the response to calcitriol treatment depends more on the severity of secondary hyperparathyroidism and the presence of confounding variables, such as hyperphosphatemia and acquired abnormalities of parathyroid cell function, than on the method of calcitriol administration.

Recent advances in intravenous calcitriol treatment

Ten years after the pioneering data by Slatopolsky, there is growing evidence that calcitriol given intravenously is able to improve secondary hyperparathyroidism better than the traditional daily oral administration. However, the scenario is changing again after the observation that oral bolus therapy, in equivalent doses to the intravenous route, is also able to effectively control parathyroid hormone secretion. This review reports and comments on the most recent controlled and uncontrolled observations dealing with calcitriol therapy of hyperparathyroidism in patients with uremia. There are currently no convincing data about the superiority of one route of administration over the other, although intravenous boluses appear to be more attractive both from a theoretical (higher plasma levels and reduced action on intestinal receptors) and practical (compliance) point of view. The higher cost of the injectable drug is the crucial factor limiting its wider clinical use. Large and carefully designed controlled clinical trials are still awaited to elucidate the most important aspects of calcitriol treatment of secondary hyperparathyroidism, such as dose, interval, and route of administration.

Prospective trial of pulse oral versus intravenous calcitriol treatment of hyperparathyroidism in ESRD

To examine the most effective route (intravenous vs. "pulse" oral), dose (physiologic vs. pharmacologic) and long-term efficacy of calcitriol therapy for secondary hyperparathyroidism in patients with end-stage renal disease (ESRD), we randomized 19 hemodialysis patients with severe hyperparathyroidism to receive over a 36-week study period either pulse orally administered calcitriol and intravenous placebo (pulse oral group; N = 9) or intravenous calcitriol and oral placebo (intravenous group; N = 10). Calcitriol was given intermittently in a double-blinded fashion at an initial dose of 2 micrograms thrice weekly and increased as tolerated up to a maximum dose of 4 micrograms per treatment. All patients received similar daily calcium supplementation (2.5 g of elemental calcium) and low dialysate calcium (1.25 mmol/liter) throughout the study period. At the maximum tolerated calcitriol dose, serum 1,25-dihydroxyvitamin D levels were significantly greater 60 minutes following intravenous (389 pmol/liter) compared to oral administration (128 pmol/liter). In spite of the different pharmacologic profiles, intravenous and oral administered calcitriol resulted in similar reductions of serum PTH over the 36 week period of observation (P = 0.300), achieving an overall maximum average PTH reduction of 43% (P = 0.016). Long-term intensive calcitriol therapy (independent of administration route), however, failed to decrease parathyroid gland size as assessed by high resolution ultrasound and/or magnetic resonance imaging. Calcitriol therapy also failed to alter the calcium sensitivity as assessed by serial PTH measurements in response to calcium loading. Increases in serum calcium, but not calcitriol dose or parathyroid gland size, predicted decrements in serum PTH, whereas hyperphosphatemia and the level of PTH suppression derived from the PTH/ionized calcium response curves predicted refractoriness to calcitriol therapy. Episodes of hypercalcemia and hyperphosphatemia were similar in both treatment groups and limited the dose of calcitriol that could be administered. These data indicate that intermittent intensive calcitriol therapy, regardless of administration route, is poorly tolerated, fails to correct parathyroid gland size and functional abnormalities, and has a limited ability to achieve sustained serum PTH reductions in end-stage renal failure patients with severe hyperparathyroidism.

Low-dose intravenous calcitriol treatment of secondary hyperparathyroidism in hemodialysis patients

Intravenous calcitriol is known to directly suppress PTH secretion and release. We evaluated the effect of four months of treatment with low-dose intravenous calcitriol on PTH levels in 83 hemodialysis patients. The criteria for including patients in the study were a serum PTH levels at least four times the normal limit, a serum total calcium less than 10 mg/dl and good control of the serum phosphorus level. All patients underwent standard bicarbonate or acetate dialysis; dialysate calcium level was maintained at the usual 3.5 mEq/liter concentration. Initial calcitriol dose was 0.87 +/- 0.02 (SEM) micrograms (0.015 micrograms/kg body wt) thrice weekly at the end of dialysis, and it was reduced in case of hypercalcemia or elevated calcium-phosphate product. Seven out of 83 patients dropped out during treatment. Among the 76 patients who completed the study, 58 (76%) showed a highly significant decrease of intact PTH levels (average reduction 48%) and of alkaline phosphatase levels after four months of therapy. Total serum calcium increased slightly but significantly in the responder group but remained unchanged in the non-responders. No significant changes in ionized calcium levels could be detected, even in responders. Treatment was well tolerated by patients, but 60% of them had transient episodes of hyperphosphatemia. Mean serum phosphate was 4.95 mg/dl at the beginning of the study. It increased significantly after four months of treatment in patients who showed a decrease of PTH levels, although it remained within acceptable limits, below 5.5 mg/dl. Twenty-eight of 76 patients (37%) reduced the dose of calcitriol because their calcium-phosphate products exceeded 60.(ABSTRACT TRUNCATED AT 250 WORDS)