When all is said and done the 29 different stimulant medication products that are on the market in the US are merely delivery systems of just two molecules, amphetamine and methylphenidate. Each formulation has advantages and disadvantages but the goal is always to get a small portion of a huge and ever-growing market for ADHD medications.
Both amphetamine and methylphenidate are unstable in water unless they are protected by some other means. If you just drop a tablet of either one in a glass of water and come back in a couple of days, all of the medication will have decomposed and will be useless. That is why we do not have a water formulation of any ADHD stimulant even though about 1/3 of children cannot swallow pills.
All of the liquid formulations (ex. Quillivant, Dyanavel, etc.) are actually suspensions of ion exchange resins that protect the molecules from the water. Don’t bother with all of this complex chemistry. All you need to know is that this is a long-winded way of answering your questions 3 ,5, and 6. The answer is “no” you can’t dissolve any other formulation (that is not already a liquid suspension and, therefore, really expensive) in any liquid and end up with a useable liquid ADHD stimulant medication.
The one exception is Vyvanse. Its delivery system is that they bond an amino acid called lysine to the amine portion of the amphetamine molecule. When they do, they get a totally inert prodrug. There is only one place on the planet that has an enzyme that cuts off the lysine and leaves the amphetamine molecule ready to do its job. That place is the inside of a human red blood cell.
As a result, the prodrug can sit in water forever and not disintegrate. The prodrug is remarkably soluable. You could take an entire month’s supply of Vyvanse and dissolve it in a teaspoon of water. Therefore, you can use as much water as you like so long as you get your math right. In the US we use ounce measures (a measure of weight) but everywhere else in the world they use milliliters (a measure of volume). I am going to assume that you are in the US for my example since our English measue is so much more complicated than metric measures.
I have a patient who is a college student who is very sensitive to dose. He has found that his optimal dose is 12 mg of Vyvanse with each dose lasting about 8 hours. At the beginning of each semester he whips up a large tupperware beaker of Vyvanse in water by dissolving the powder inside twelve (12) capsules of the 70 mg size capsules of Vyvanse in 70 ounces of water (8 3/4 cups). He shakes it up and lets the white powder fall to the bottom. Each ounce now has 12 mg of Vyvanse. Each morning he pours out a shot glass (1 oz.) of the liquid and goes off to class. 7 1/2 hours later he takes another ounce so that he can study at night. He gets almost 6 dose out of a single Vyvanse capsule. Pretty thrifty. Put a label on the beaker and hide it some place where people won’t get into it. It does not need to be refrigerated.
If you have any more questions or if you would like someone to check your math, let me know.