Pharmacological Management of Secondary Hyperparathyroidism in Patients with Chronic Kidney Disease.

Secondary hyperparathyroidism (SHPT) is a common complication of chronic kidney disease (CKD) and is part of the CKD-mineral bone disorder (CKD-MBD). SHPT is associated with increased risk of fracture and mortality; thus, SHPT control is recommended as kidney function declines. Effective SHPT management becomes more difficult once skeletal and cardiovascular adverse effects associated with severe SHPT have become established. However, interventional studies to lower parathyroid hormone (PTH) have so far shown inconsistent results in improving patient-centred outcomes such as mortality, cardiovascular events and fracture. Pharmacological treatment effect on PTH level is also inconsistent between pre-dialysis CKD and dialysis patients, which adds to the complexity of SHPT management. This review aims to give an overview on the pathophysiology, pharmacological and non-pharmacological treatment for SHPT in CKD including some of the limitations of current therapeutic options.

Encapsulating peritoneal sclerosis: clinical significance and implications.

Encapsulating peritoneal sclerosis (EPS) is a rare but serious complication of peritoneal dialysis (PD). This review discusses the current understanding of the aetiology and pathogenesis of EPS, highlighting histological features which differentiate it from simple sclerosis of the peritoneal membrane which develops with time on PD. Diagnostic criteria are presented, including the role of imaging techniques. To date there are no randomised controlled trials to guide therapy; however, surgical techniques are an important treatment option. Collaborative research will be essential if this serious problem facing PD is to be solved.

Sclerosing encapsulating peritonitis: a case series from a single U.K. center during a 10-year period.

Sclerosing encapsulating peritonitis (SEP) is a serious complication of peritoneal dialysis (PD). Previous reports place the prevalence of SEP at 0.54%-7.3%. We estimated the prevalence of SEP in our unit to be 1.4% over the period 1989-1999. We here present the 6 identified cases. All of the patients presented with small-bowel obstruction; hemorrhagic ascites was identified in 3 cases. All 6 patients experienced ultrafiltration inadequacy, and 5 were treated with glucose polymer (icodextrin; duration of treatment: 1 month-2.5 years). Peritoneal dialysis was stopped at the time of diagnosis in 2 cases. In the other 4 cases, PD had been withdrawn some time prior to the SEP being diagnosed (2 weeks-5 years). Five of the patients have died; the 6th currently uses hemodialysis.

The effects of dose, nutrition, and age on hexarelin-induced anterior pituitary hormone secretion in adult patients on maintenance hemodialysis.

Malnutrition is common in chronic renal failure (CRF) and adversely affects prognosis. In view of the anabolic action of GH in CRF, we have studied the effects of hexarelin, a GH secretagogue, on CRF. An iv dose-response study in six 20- to 40-yr-old well nourished hemodialysis (HD) patients was followed by administration of the maximally effective dose to six 20- to 40-yr-old healthy controls, six 20- to 40-yr-old poorly nourished HD patients, and six 50- to 70-yr-old poorly nourished HD patients. GH secretion (area under the curve over 180 min, mean +/- SE) after 2 and 1 microg/kg doses (10.7 +/- 4.2 and 8.2 +/- 5.2 min/U x L, respectively) was greater than after placebo (0.60 +/- 0.11 min/U x L; P < 0.001 and P < 0.05, respectively). The most effective dose (2 microg/kg) produced similar GH secretion (11.4 +/- 3.3 min/U x L) in controls. GH secretion in the younger poorly nourished HD group (19.0 +/- 4.4 min/U x L) was not significantly different from that in the well nourished 20- to 40-yr-old HD patients (P = 0.06). GH secretion in the older, poorly nourished HD patients (9.4 +/- 2.2 min/U x L) was similar to that in the young, poorly nourished group (P = 0.18). ACTH and cortisol concentrations increased in all groups, whereas PRL concentrations were not affected in CRF. The profound action of hexarelin on GH secretion has been shown to extend to CRF. Trends were evident toward increasing efficacy in malnourished subjects and decreasing efficacy with age. Further studies are required to determine whether the acute actions of hexarelin can be translated into long term anabolic changes.

A double-blind, randomized, placebo-controlled study of nifedipine on early renal allograft function.

A double-blind, randomized, placebo-controlled study was conducted to determine the effect of nifedipine on early renal allograft function when added to a triple therapy immunosuppression regime comprising low-dose cyclosporin (CsA), prednisolone and azathioprine. Fifty adult cadaveric renal allograft recipients were randomized to placebo (group P n = 17), nifedipine 10 mg preoperatively and 20 mg b.d. postoperatively for 48 h, followed by matching placebo for 3 months (group NS n = 16) or nifedipine 10 mg preoperatively and 20 mg b.d. postoperatively for 3 months (group NL n = 17). Donor and recipient exclusion criteria included recent calcium antagonist treatment. At 3 months after transplantation mean GFR adjusted for graft loss was significantly higher in group NL than in NS (mean +/- SD 61 +/- 28 versus 34 +/- 25 ml/min/1.73 m2; P < 0.05), group P being intermediate (45 +/- 34 ml/min/1.73 m2). Similarly, effective renal blood flow (ERBF) at 3 months was higher in group NL than in groups P and NS (mean +/- SD 351 +/- 175 versus 216 +/- 166 and 220 +/- 162 ml/min/1.73 m2; P < 0.05). The differences were not significant by 6 months post-transplantation. This study suggests that oral nifedipine commenced preoperatively and continued for 3 months following transplantation has beneficial effects on early renal allograft function when incorporated as part of an immunotherapy regimen based on cyclosporin.

Dual energy X-ray absorptiometry versus skinfold measurements in the assessment of total body fat in renal transplant recipients.

Traditional methods for estimating total body fat rely on the assumption that body fat distribution and bone mineral content are constant. However, in patients undergoing renal transplantation rapid changes in body composition occur, with variations in fat distribution and bone mineral content. In order to determine the reliability of skinfold measurement (SFM) in these patients, we compared it with dual energy X-ray absorptiometry (DEXA), which estimates body composition without reliance on assumptions of constant fat distribution and bone mineral content. Thirty-four adult renal transplant recipients were studied at the time of transplantation and again after 3 and 6 months. The correlation coefficients of DEXA vs SFM at the three time points were 0.84, 0.78, 0.85, respectively (P = 0.0001). In 34 healthy adults serving as controls, the correlation coefficient was 0.95 (P = 0.0001). Total body fat increased progressively following renal transplantation (P < 0.03 by 6 months) with SFM showing considerable disagreement with DEXA measurements of percentage total body fat. Thus skinfold measurements underestimated changes in total body fat following renal transplantation, especially in those gaining substantial amounts of body fat, and DEXA appeared to be a more appropriate technique.

Effects of metronidazole and misoprostol on indomethacin-induced changes in intestinal permeability.

In previous open studies, misoprostol and metronidazole reduced nonsteroidal anti-inflammatory drug-induced intestinal permeability changes and inflammation respectively. We assessed the effects of indomethacin treatment (50 mg three times a day) for one week with either coadministered metronidazole (400 mg twice a day, group 1, N = 9) or misoprostol (200 micrograms four times a day, group 2, N = 7) on intestinal permeability to [51Cr]EDTA and mannitol in healthy volunteers, using double-blind, placebo-controlled, randomized techniques. Given alone, neither metronidazole nor misoprostol affected [51Cr]EDTA permeation, whereas indomethacin alone increased it from 1.20 (0.40) [mean percent urinary recovery (SD) groups 1 and 2] to 2.43 (0.72), P < 0.002. Coadministered metronidazole (group 1) prevented this increase [1.10 (0.39) before, 1.55 (0.54) after, P > 0.05], whereas misoprostol (group 2) did not [1.31 (0.51) before, 3.26 (1.10) after, P = 0.005]. No drug regimen altered mannitol permeation. Indomethacin and misoprostol did not affect urinary recovery of intravenously administered probes. The results with metronidazole, if related to its antibacterial effects, support evidence from animal models that bacteria contribute to NSAID-induced intestinal damage. The previously reported reduction of indomethacin-induced increased permeability by misoprostol during a one-day study is not seen when the drugs are used in standard clinical doses for one week.

Effects of indomethacin and misoprostol on renal function in healthy volunteers.

We have examined the effects on renal function of indomethacin and misoprostol, alone and in combination. Eight healthy volunteers took indomethacin 50 mg tds for one week, and indomethacin plus misoprostol (a synthetic PGE1 analogue) 200 micrograms qds for one week in a crossover design. A separate group (n = 5) took misoprostol alone for one week. 51Cr EDTA GFR rose significantly from baseline after the combination of indomethacin and misoprostol (from mean +/- SD 117 +/- 7.1 to 123 +/- 8.0 mls/min/1.73 m2, p = 0.05). When indomethacin alone was given 51Cr EDTA GFR did not change significantly (120 +/- 9.0 to 117 +/- 9.0 mls/min/1.73 m2). However in 4 of these subjects 51Cr EDTA GFR fell (range 7-19 mls/min/1.73 m2); in each of these the reduction was reversed when the indomethacin was given together with misoprostol. In the whole group the change in 51Cr EDTA GFR, from baseline, after indomethacin plus misoprostol was significantly different from that after indomethacin alone (+6 +/- 8 vs -3 +/- 5 mls/min/1.73 m2 p = 0.05). Misoprostol alone had no effect on GFR. We conclude that misoprostol and indomethacin in combination increase GFR in healthy volunteers, and further studies are now warranted to determine whether misoprostol is beneficial in the prophylaxis and treatment of NSAID-induced renal impairment.

Does the arteriovenous fistula in chronic haemodialysis patients stimulate endothelin-1 release?

Plasma endothelin-1 (ET-1)-like immunoreactivity was measured by radioimmune assay in predialysis plasma samples from 16 chronic haemodialysis patients (7 dialysing through arteriovenous (AV) fistulae and 9 using central venous cannulae for access), from 10 patients with functioning renal transplants (5 with AV fistulae and 5 without), and from 6 healthy subjects as controls. Among dialysis patients, ET-1 was greater in those with AV fistulae than in those using cannulae for dialysis (median (range), 5.5 (3.1) pM versus 3.7 (2.0) pM, P = 0.02), and in all haemodialysis patients ET-1 values were substantially greater than in normal controls (3.9 (3.2) pM versus 0.5 (0.1) pM; P = 0.001). In patients with functioning AV fistulae, ET-1 concentrations obtained directly from the AV anastomosis of the fistula (4.4 (3.0) pM) were less than those taken simultaneously from the contralateral arm (5.5 (3.1) pM; P = 0.04), while samples drawn from the venous side of the fistula were intermediate (4.6 (3.4) pM). In renal transplant recipients, ET-1 values did not differ significantly from those in control subjects (0.7 (1.9) pM versus 0.5 (0.1) pM, n.s.), but in these patients there was a significant difference between peripheral venous ET-1 in transplant patients with and without AV fistulae (0.8 (1.9) pM versus 0.6 (1.1) pM respectively, P = 0.04). The results suggest that the increased blood flow rate through the arterialized venous circulation in the fistula arm stimulates increased ET-1 release in these patients, and that this accounts, at least in part, for the increased ET-1 found in the patients with functioning AV fistulae.

Hypoxia-induced von Willebrand factor release is blocked by verapamil.

Hypoxia-induced stimulation of the rate of von Willebrand factor (vWF) release from human umbilical vein endothelial cells in culture, and the influence of the calcium antagonist verapamil, was studied using a system in which a pO2 of 20 mm Hg was achieved over 60 min. The mean +/- SEM rate of vWF release over 60 min in normoxia was 0.42 +/- 0.07% pooled plasma standard. The addition of verapamil did not alter the basal rate of vWF release, but after 60 min of hypoxia, the rate was increased to 0.71 +/- 0.03% plasma standard (p < 0.01). Verapamil at a concentration of 0.1 microgram/ml of media had no influence on the stimulated rate of release (0.78 +/- 0.07%), but increasing concentrations of verapamil up to a maximum of 1 microgram/ml attenuated the hypoxia induced stimulation (0.48 +/- 0.07%; p = 0.04 vs. hypoxic control). Thus, verapamil at this concentration completely blocked the hypoxia-induced stimulation.