If minoxidil is soluble in alcohol only to ~5%, how can you make a true 12.5% solution?
A. According to Remington’s Pharmaceutical Science (20th Edition), minoxidil is soluble to the extent of “1gm in 25ml alcohol” (4% solution). When the solution is acidified, for example by azelaic acid, the solubility is increased to approximately 5%. With the addition of propylene glycol or glycerin, a true 5% minoxidil solution can be stabilized.
