Formation and properties of magnesium-ammonium-phosphate hexahydrate biocements in the Ca-Mg-PO4 system.

Calcium substituted trimagnesium phosphate with the general formula Ca(x)Mg((3-x))(PO(4))(2) (0 < x < 1.5) was synthesized by calcination of powder mixtures with the appropriate stoichiometry and reacted with 3.5 M diammonium hydrogenphosphate solution to form a cementitious matrix of magnesium ammonium phosphate hexahydrate (struvite). The degree of ionic substitution was shown to influence physical cement properties; clinically suitable cement formulations with setting times in the range 5-15 min and compressive strengths of >50 MPa were obtained for x ≤ 0.75 together with a grinding time ≥ 1 h and a powder to liquid ratio ≥ 2.5 g/ml. The cement cytocompatibility was investigated by culturing human osteoblast cell line MG63 on cement surfaces demonstrating pronounced cell growth during 13 days cultivation.

Effect of drospirenone on serum potassium and drospirenone pharmacokinetics in women with normal or impaired renal function.

This open-label study investigated whether drospirenone, a novel progestin with antimineralocorticoid properties, increases the risk for hyperkalemia in subjects with renal impairment. Women with normal renal function and mild or moderate renal impairment were given drospirenone 3 mg/d for 14 days. Mean serum potassium concentrations did not significantly change during steady-state drospirenone treatment. No difference in drospirenone effects on serum potassium concentrations in subjects with renal insufficiency versus subjects with normal renal function was found. Steady-state pharmacokinetics was similar in subjects with normal renal function and mild renal impairment, whereas, due to results from 1 subject, drospirenone exposure was slightly higher in the moderate renal impairment group. Given the reported tolerability of drospirenone, this small increase in serum drospirenone is not expected to be clinically significant. In conclusion, this study demonstrated that drospirenone has no significant effect on serum potassium levels in patients with mild to moderate renal insufficiency.