I apologize if what I'm about to say has been repeated but I want to attempt to clarify and educate those who are interested in Vyvanse...
...especially those who may be curious about intravenous route of ingestion...
Lis-dexamphetamine (Vyvanse) is water-soluble (792 mg/mL). The reason it is considered a pro-drug is because the amino acid lysine is attached to the dex-amphetamine molecule (very similar to the adderall molecule). This causes the drug Vyvanse to be metabolized by the body at a more stable constant rate (preventing overdoses).
Although, the gastro-intestinal system contains enzymes (like proteases, trypsin) that breakdown this pro-drug to its most efficient form, enzymes are not solely needed to cleave the amino acid lysine. A moderately strong aqueous acid solution will work. Emphasis here is that it will work to an extent, nothing will work as well as your digestive system will. However, as a very general rule, anything water-soluble at room temperature will travel through your blood and to eventually to your liver where it, along with all blood, is filtered. Therefore...
Safest way:
-Let it dissolve in room temperature DI (de-ionized) water for 25-30 min. Distilled water is safe as well
-Filter at least 2x
-To the Moon!
More dangerous way:
-Let it dissolve in a mixture of a weak acid (lemon/grapefruit/orange juice, vinegar, ascorbic acid a.k.a. Vitamin C) + room temperature DI water in a 4:1 ratio for 15-20 min.
-Filter at least 2x
-Good Luck!
The second method is more dangerous because you must take into consideration the possible bacteria (acidophiles) within the acidic fruit juice or vinegar. Remember, aseptic technique (performing under sterile conditions) is key for intravenous use!