The reason amphetamines are used for ADHD but not depression is that they've been studied to show that the ADHD improving effect can remain for many months, while the mood-improving effect will taper off quickly if you take them every day. Almost everyone who takes ADHD stimulant, feels a mood and motivation boost ("so happy I could cry" is the common phrase) and then is disappointed when that mood boost stops happening after a few weeks or months will learn this. Attention enhancement is less prone to tolerance, though it still accumulates tolerance too. There are some studies showing that the effects of stimulants in ADHD diminish substantially on a multi-year time frame, and it's probably not a coincidence that many people (though not all) who take stimulants discontinue after several years.
Most abusers of methamphetamine are not taking it orally (slow route of administration) and are generally using much higher relative dosing than ADHD patients are using amphetamines. Potential for addiction and other physical harms are greatly affected by both of those things, so the comparison has some truth, but is obviously sensationalized.
If one could 'add meth'(??) to chemicals to make them more potent, without changing the chemical, it would be the difference between (for example) citric acid and really strong citric acid, or codeine 2.5mg and codeine 5mg.
You'll note that neither of these involves changing the name of the chemical, because that is not how chemical names work.
As someone else has pointed out, the difference between 'hydrogen monoxide' and 'dihydrogen monoxide' isn't 'it's like hydrogen monoxide with added di', because that is ridiculous.
Please stop saying anything beginning with 'meth' is just meth with added bits.
It's a really odd misinterpretation of the terrible dangers of: methane, Methodists, methanol, Methaemoglobin, methicillin, etc.
It's pretty reasonable to expect reversing DAT and inhibiting VMAT2 increases oxidative flux, the question is really how much not if. Methheads certainly get "brain damage", but is nudging the average loss from 5-10% to 7-12% "damage"? Is it meaningful? Over 30, 40 years that could very well add up.
A typical legitimate therapeutic methamphetamine dose is around ~20mg (up to maybe 60mg a day). A typical dose used by addicts is around 1 gram. And it's usually smoked, resulting in immediate bioavailability.
Not that it matters that much. It's no wonder that it fries your brain when you're using 25 _times_ the normal therapeutic dose.
These days formulations like lisdexamfetamine and extended release methylphenidate are preferred because they have all-day efficacy with typical duration of action of around 8-12h which carries lower abuse potential.
The benefit is that the medication automatically produces a smooth effects profile allowing you to live your life without timing medication to perfection.
A pronounced come-up and crash is a risk factor for abuse and addiction, so smoothing or removing the peaks and valleys is important.
(As an aside, there are more complex extended release mechanisms than just delayed bead release - like lisfexamfetamine is a inactive prodrug, so cleaving the lysine off the amphetamine is rate limited. This has the effect of extended the duration of effect, and reduces the potential to abuse by snorting/iv/etc).
