This section is from the book "Materia Medica And Therapeutics Inorganic Substances", by Charles D. F. Phillips. Also available from Amazon: Materia medica and therapeutics.
The power of magnesia to dissolve uric acid and to lessen its formation, whether directly or indirectly, has already been mentioned. Among other instances, Mr. Brande records that of a man, aged sixty, accustomed to pass much uric acid, and even calculi, and who had taken daily either 9 dr. of "subcarbonate" of soda, or 3 of potash, for more than a year without good effect, yet under the use of 60 gr. of magnesia thrice a day the acid soon diminished in amount, and after three weeks of continuous treatment it seldom recurred. Since Mr. Brande's memoir (1810) the remedy has been often used in similar cases. Sir B. Brodie combined 6 gr. of magnesia with 12 of potash bicarbonate and 15 of bitartrate, and it often acted well.