Potassium-magnesium citrate is an effective prophylaxis against recurrent calcium oxalate nephrolithiasis

Inhibitors and promoters of stone formation.

Physicochemical aspects of urolithiasis.

Objective To evaluate the effect of an aqueous extract of Phyllanthus niruri (Pn), a plant used in folk medicine to treat lithiasis, on the urinary excretion of endogenous inhibitors of lithogenesis, citrate, magnesium and glycosaminoglycans (GAGs).



Materials and methods The effect of chronic (42 days) administration of Pn (1.25 mg/mL/day, orally) was evaluated in a rat model of urolithiasis induced by the introduction of a calcium oxalate (CaOx) seed into the bladder of adult male Wistar rats. The animals were divided into four groups: a sham control (16 rats); a control+Pn (six); CaOx+water instead of Pn (14); and CaOx+Pn (22). Plasma and urine were collected after 42 days of treatment for biochemical analysis and the determination of urinary excretion of citrate, magnesium and GAGs. The animals were then killed and the calculi analysed.



Results The creatinine clearance or urinary and plasma concentrations of Na+, K+, Ca2+, oxalate, phosphate and uric acid were unaffected by Pn or the induction of lithiasis. Treatment with Pn strongly inhibited the growth of the matrix calculus and reduced the number of stone satellites compared with the group receiving water. The calculi were eliminated or dissolved in some treated animals (three of 22). The urinary excretion of citrate and magnesium was unaffected by Pn treatment. However, the mean (sd) urinary concentration of GAGs was significantly lower in rats treated with CaOx+Pn, at 5.64 (0.86) mg/g creatinine, than when treated with CaOx + water, at 11.78 (2.21) mg/g creatinine. In contrast, the content of GAGs in the calculi was higher in the CaOx + Pn rats, at 48.0 (10.4) g/g calculus, than in the CaOx + water group, at 16.6 (9.6) g/g calculus.



Conclusion These results show that Pn has an inhibitory effect on crystal growth, which is independent of changes in the urinary excretion of citrate and Mg, but might be related to the higher incorporation of GAGs into the calculi.

https://onlinelibrary.wiley.com/doi/pdf/10.1046/j.1464-410X.2002.02794.x

The effect of Phyllanthus niruri on urinary inhibitors of calcium oxalate crystallization and other factors associated with renal stone formation

Factors determining types and morphologies of calcium oxalate crystals: molar concentrations, buffering, pH, stirring and temperature.

The kinetics of the crystal growth of calcium oxalate monohydrate has been studied using the technique of seeded crystal growth from stable supersaturated solution. The rate law takes the form minus dc/dt equals kN-2 in which the rate of loss of lattice ion from solution is proportional to the square of the supersaturation. It is proposed that the incorporation of lattice ions into the crystal is governed by a bimolecular surface-controlled reaction step. The rate is independent of the hydrodynamics of the system but is proportional to the solid to solution ratio in the supersaturated solution. The specific rate constant, k (M-minus-1 min-minus-1 [mg/dl]minus-1), is nearly independent of the solid to solution ratio, however. The rate of crystal growth was found not to vary with the calcium to oxalate molar ratio in the range 1.5 to 0.75, although the rate did increase at both higher and lower ratios. The method was found to be simple, rapid, and reproducible and lends itself to the quantitative study of inhibitors of crystal growth.

Meyer Jl

Papers

Growth of calcium oxalate crystals. I. A model for urinary stone growth.