Sevelamer HCl

Sevelamer HCl

Transient acid exposure increases sevelamer HCl phosphate binding.[Pubmed:17506513]

J Pharm Sci. 2007 Aug;96(8):2154-60.

The patient-to-patient variability in the dosing of Sevelamer HCl for phosphate control led us to test whether the binder's transient exposure to acidic environments (such as the stomach) might alter the compound so as to change its subsequent binding capacity in the more alkaline small intestine. We hypothesized that an acid milieu could either increase the reactive sites (protonated amine groups) or make the polymer more hydrophilic (hydration and swelling allowing more phosphate to reach those sites). Eight hundred milligrams of Renagel tablets were exposed to pHs 1, 2.3, and 7 (n = 7 each acidity level) for 1 h. NaCl was added to keep ionic strength the same. Measured by atomic emission phosphate uptake after 3 h at pH 7 was, respectively, 3.13 +/- 0.21, 2.72 +/- 0.35, and 1.85 +/- 0.46 mequiv./g (p = 0.0006, pH 1 vs. pH 7). Semi-automated computerized image analysis was then performed to measure swelling of the particles. We constructed a glass continuous-flow cell that allowed stationary particles and real-time photography. Using digitized optical measurements there was no difference (p > 0.8) between the swelling after 1 h of pH 1 or 7 solutions (60.2 +/- 14.8% vs. 59.5 +/- 9.8% increase in diameter). Our findings support the importance of transient acid exposure in enhancing phosphate binding, due to increased protonated sites rather than by more swelling. Patients with acquired or pharmacologic achlorhydria would not benefit from this unexpected in vivo reaction. Possibly manufacturing sevelamer with a higher degree of protonation or administering it with appropriately acidic vehicles or beverages remains to be investigated.

[Relationship between sevelamer HCl and vascular calcification].[Pubmed:17339744]

Clin Calcium. 2007 Mar;17(3):392-8.

The Kidney Disease Outcomes Quality Initiative (K/DOQI) issued "Clinical Practice Guidelines for Bone Metabolism and Disease in Chronic Kidney Disease", in which it is recommended that the level of intact parathyroid hormone (i-PTH) should be kept at 150 - 300 pg/mL, the serum phosphorus (P) level at 3.5 - 5.5 mg/dL, and the serum calcium (Ca) level within the normal range of laboratory values (8.4 - 9.5 mg/mL, as close to the lower limit as possible). In developing these guidelines, the K/DOQI apparently considered the recently established fact that control of Ca, P and PTH influences not only the development of bone lesions but also patient prognostic factors such as arteriosclerosis, ectopic calcification, and cardiovascular complications, as well as the development of various vitamin D products and analogues and new P adsorbents. The Japanese guidelines also emphasize the control of P and Ca, rather than PTH. Therefore Phosphorus control is a primary goal in the care of patients with end-stage renal disease. We inspect the relationship between Vascular calcification and Sevelamer HCl, a non-aluminium, non-calcium, non-absorbed phosphate binder.

Spontaneous carbonate formation in an amorphous, amine-rich, polymeric drug substance: sevelamer HCl product quality.[Pubmed:22700351]

J Pharm Sci. 2012 Aug;101(8):2681-5.

Spectral differences among multiple manufacturers/lots of Sevelamer HCl were observed by Fourier transform infrared spectroscopy, and further characterization was performed to identify the cause for these differences. The drug substance is a polymer that possesses a large molecular weight, is amorphous, and is practically insoluble in both water and organic solvents. Thus, solid-state characterization methods (spectroscopic and thermal) were required to identify and characterize differences among the samples to assess possible differences in product quality. (1)(3)C cross-polarization-magic-angle-spinning nuclear magnetic resonance spectroscopy of Sevelamer HCl substances demonstrated the presence of a carbonyl-containing species, which was attributed to a carbonate impurity among samples. Stability studies demonstrated that this carbonate impurity formed spontaneously upon exposure of the drug substance to atmospheric water vapor and carbon dioxide, even under ambient conditions. Mechanistically, this behavior likely arises from the large number of primary and secondary amine groups, the hygroscopicity of the HCl salt, and a high degree of molecular mobility due to the amorphous nature of the drug substance.

Lanthanum carbonate, like sevelamer-HCl, retards the progression of vascular calcification and atherosclerosis in uremic apolipoprotein E-deficient mice.[Pubmed:21705467]

Nephrol Dial Transplant. 2012 Feb;27(2):505-13.

BACKGROUND: Atherosclerosis and vascular calcification (VC) progression in chronic kidney disease is favored by disturbances of mineral metabolism. We compared the effect of phosphate binder lanthanum (La) carbonate with sevelamer-HCl on atherosclerosis, VC and bone structure and function in mice with chronic renal failure (CRF). METHODS: Apolipoprotein E-deficient (apoE(-/-)) mice were randomized to one non-CRF and three CRF groups, fed with standard diet (one non-CRF and one CRF) or diet supplemented with either 3% lanthanum carbonate (La3%) or 3% sevelamer-HCl (Sev3%). RESULTS: Both La3% and Sev3% supplemented CRF mice displayed a decrease of serum phosphorus, calcification at both intimal and medial aortic sites and atherosclerosis. This was associated with a reduction of plaque Type I collagen expression by both binders and of positive nitrotyrosine staining in response to sevelamer-HCl only. Increased mineral apposition and bone formation rates in unsupplemented CRF mice were reduced by Sev3% but not by La3%. CONCLUSIONS: The beneficial effects of La carbonate and sevelamer-HCl on the progression of VC and atherosclerosis in CRF mice could be mainly due to a decrease in phosphate retention and likewise a reduction of arterial Type I collagen expression. The effect of La carbonate differed from that of sevelamer-HCl in that it did not appear to exert its vascular effects via changes in oxidative stress or bone remodeling in the present model.

Sevelamer hydrochloride is a phosphate binding drug used to treat hyperphosphatemia in patients with chronic kidney disease; consists of polyallylamine that is crosslinked with epichlorohydrin.

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