Edition: BP 2025 (Ph. Eur. 11.6 update)
Action and use
Used in the treatment of magnesium deficiency.
DEFINITION
Magnesium Glycerophosphate Chewable Tablets contain Magnesium Glycerophosphate.
The tablets comply with the requirements stated under Tablets and with the following requirements. Where appropriate, the tablets also comply with the requirements stated under Unlicensed Medicines.
Content of magnesium, Mg
95.0 to 105.0% of the stated amount.
IDENTIFICATION
A. To a quantity of the powdered tablets containing the equivalent of about 25 mg of magnesium in a test tube fitted with a glass tube add 1 g of potassium hydrogen sulfate. Heat strongly and direct the white vapour towards a piece of filter paper impregnated with a freshly prepared 1% w/v solution of sodium nitroprusside. The filter paper develops a blue colour in contact with piperidine.
B. Place a quantity of the powdered tablets containing the equivalent of about 25 mg of magnesium in a crucible and ignite. Take up the residue with 5 mL of nitric acid, heat on a water-bath for 1 minute and filter. The filtrate yields reaction B characteristic of phosphates, Appendix VI.
C. Dissolve a quantity of the powdered tablets containing the equivalent of about 25 mg of magnesium in 10 mL of water and filter. The filtrate yields reaction A characteristic of magnesium salts, Appendix VI.
TESTS
Disintegration
The requirement for Disintegration does not apply to Chewable Magnesium Glycerophosphate Tablets.
Phosphate
Dissolve a quantity of the powdered tablets containing the equivalent of about 25 mg of magnesium in 100 mL of water and dilute 1 mL of the solution to 100 mL with water. The resulting solution complies with the limit test for phosphates, Appendix VII (0.5%).
ASSAY
Weigh and powder 20 tablets. Dissolve a quantity of the powder containing the equivalent of about 120 mg of magnesium in 25 mL of water. Transfer 10 mL of the solution into a 500 mL conical flask and carry out the complexometric titration of magnesium, Appendix VIII D, beginning at the words ‘… and dilute to 300 mL with water’. Each mL of 0.1M disodium edetate VS is equivalent to 2.431 mg of Mg.
LABELLING
The label states the quantity of active ingredient both in terms of the amount of Magnesium Glycerophosphate and in terms of the equivalent amount of magnesium or magnesium ions (Mg2+).
Tablets containing 1 gram of Magnesium Glycerophosphate contain approximately 97 mg of magnesium and approximately 4 millimoles of magnesium ions (4 mmol Mg2+) per tablet.
