Originally Posted by Eya724
Okay, but does that mean you would need a more alkaline or acidic pH?? (my major was Environmental Biology, not Chemistry or Pharmacology)
Short answer: more alkaline.
There's no direct evidence that gastrointestinal pH will affect the absorption of lisdexamfetamine, but what I was saying is that it's possible that increased acidity (contrary to the general advice when it comes to amphetamines) with
the lisdexamfetamine (so something acidic anytime from 30 minutes before up until actually taking lisdexamfetamine), may
allow the pancreatic enzyme, trypsin, to have a significant effect by increasing its secretion. The idea is that this could help by cleaving the d-amph from lisdexamfetamine while in the GI tract, but at the same time, the acidic environment would work against the absorption of that cleaved d-amph, so this may or may not have a significant overall effect.
have an overall effect is a more alkaline
urinary pH, which can be achieved with an antacid (specifically systemic antacids, though some nonsystemic antacids like magnesium hydroxide can also have an alkalizing effect on urinary pH). This decreases the elimination of unmetabolized amphetamine
(but not unchanged lisdexamfetamine!). In other words, having more alkaline urine increases the elimination half life of amphetamine, giving unmetabolized amphetamine more of a chance to exert psychoactive
effects (for more time). This should be more effective with non-prodrug formulations of (d-)amphetamine, but it still applies to lisdexamfetamine once it has been bioactivated.
Originally Posted by Eya724
What effect do you think drinking a solution of sodium bicarbonate (baking soda and water) would have then, and when would be the ideal time after dosing to try that?
As explained above, the effect would be reduced elimination of unmetabolized dextroamphetamine. As long as the urinary pH is made more alkaline by the alkalizing agent before amphetamine may be eliminated, then obviously it should be effective, so I think drinking this solution up to 30 minutes before taking lisdexamfetamine would be a good general rule of thumb. However, sodium bicarbonate is a short-acting alkalizing agent and you'd need to re-dose frequently to really take advantage of how raising (alkalizing) the urinary pH affects d-amphetamine elimination, particularly in the case of this prodrug formulation (where d-amphetamine reaches maximum plasma concentration nearly 4 hours after ingestion). A more convenient antacid agent should be considered, such as the H2
antagonists (cimetidine, famotidine, rantidine, etc.), or a proton pump inhibitor like omeprazole.
Please also note the potential influence on any other medications/substances (prescription, OTC, recreational or "research" alike). For instance, more alkaline urine can decrease the effect of salicylic acid (main metabolite of acetylsalicylic acid, or aspirin). Furthermore, chronic antacid use/alkalized urine can lead to plenty of complications, such as kidney stones, so please understand and appreciate the complexity involved and consider your overall health before making any large change to your normal regimen.
Hope that helps