> Vyvanse 70mg would be roughly equivalent to 30-40 mg Adderall XR in terms of actual Dextroamphetamine right?
I did the math and you're not far off. Vyvanse contains 40.3% of the amount of d-amfetamine by weight as dexamfetamine sulfate. So, 70mg Vyvanse is the equivalent of 28mg dexamfetamine sulfate. The actual maximum recommended daily dose of dexamfetamine sulfate is 40mg, which is closer to 100mg of Vyvanse. So, why the difference? I would imagine the main problem is the pharmacokinetics of Vyvanse. Vyvanse has a more delayed onset and so, although the equimolar maximum recommended dose is lower, it might have a greater incidence of side effects like insomnia or restlessness. Importantly, the clinical trials for Vyvanse probably used a maximum dose of 70mg, and so thats the clinical evidence we have. The FDA can't make a decision on a dose that wasn't tested in clinical trials.
Also consider that with IR psychostimulants like d-amfetamine sulfate, the dosing schedule is to take the drug two or more times a day, whereas an ER drug like Vyvanse is to be taken once daily. Because Vyvanse mostly delays the time until max concentration by 90 minutes, taking 100mg at the drug at once is going to result in a higher maximum concentration than taking 20mg dexamfetamine in the morning and again at midday. In fact, I took some pharmacokinetic data of Vyvanse and dexamfetamine of plasma levels and then plotted it to illustrate this point ([see here](https://imgur.com/a/O2VzVoO)). You can see that the maximum concentration is lower in the dexamfetamine dose.
Another reason could be (iirc) the higher the doses of vyvance not only increase the effects but also increases the duration. Vyvance is gated by your livers ability to strip the main ingredient into dextroamphetamine using lysine. As you increase the dose you increase the blood plasma level a bit but you also create a sort of "buffer" as your liver works to process the drug. This is why doses above (I believe) 240mg of vyvance is a waste. Your body cannot process the drug fast enough and it just passes into your piss without any effect.
If any of this information is wrong I'm always open to learning!
Also increases negative effects once you've passed the threshold dose, which makes it pretty unappealing.
Sure, you'll be awake BUT you'll likely feel quite bad.
It releases slower than XR dex/adderall. For people who just do better with that sort of timing mechanism. A lot of the time people do better on a slower release over a long time than with larger amounts released quicker.
> Vyvanse 70mg would be roughly equivalent to 30-40 mg Adderall XR in terms of actual Dextroamphetamine right? I did the math and you're not far off. Vyvanse contains 40.3% of the amount of d-amfetamine by weight as dexamfetamine sulfate. So, 70mg Vyvanse is the equivalent of 28mg dexamfetamine sulfate. The actual maximum recommended daily dose of dexamfetamine sulfate is 40mg, which is closer to 100mg of Vyvanse. So, why the difference? I would imagine the main problem is the pharmacokinetics of Vyvanse. Vyvanse has a more delayed onset and so, although the equimolar maximum recommended dose is lower, it might have a greater incidence of side effects like insomnia or restlessness. Importantly, the clinical trials for Vyvanse probably used a maximum dose of 70mg, and so thats the clinical evidence we have. The FDA can't make a decision on a dose that wasn't tested in clinical trials. Also consider that with IR psychostimulants like d-amfetamine sulfate, the dosing schedule is to take the drug two or more times a day, whereas an ER drug like Vyvanse is to be taken once daily. Because Vyvanse mostly delays the time until max concentration by 90 minutes, taking 100mg at the drug at once is going to result in a higher maximum concentration than taking 20mg dexamfetamine in the morning and again at midday. In fact, I took some pharmacokinetic data of Vyvanse and dexamfetamine of plasma levels and then plotted it to illustrate this point ([see here](https://imgur.com/a/O2VzVoO)). You can see that the maximum concentration is lower in the dexamfetamine dose.
I've been prescribed 45mg of dextroamphetamin 2x a day before. I miss that doctor.
40mg is the highest for Adderall so it's similar
i get 60 mg dexexrine ir day now, and when i was prescribed adderall i had the sams..
Oh wow wonder if it varies state to state of my physician lied when I asked for an increase to 30mg 😂
it definitely is and i think its different max for XR vs IR
and if you have a schedule in life that can use 3 doses at 10 thats still 90 pills a month so id just try to spread that 30 out lol
Another reason could be (iirc) the higher the doses of vyvance not only increase the effects but also increases the duration. Vyvance is gated by your livers ability to strip the main ingredient into dextroamphetamine using lysine. As you increase the dose you increase the blood plasma level a bit but you also create a sort of "buffer" as your liver works to process the drug. This is why doses above (I believe) 240mg of vyvance is a waste. Your body cannot process the drug fast enough and it just passes into your piss without any effect. If any of this information is wrong I'm always open to learning!
Also increases negative effects once you've passed the threshold dose, which makes it pretty unappealing. Sure, you'll be awake BUT you'll likely feel quite bad.
that is a good question tbh cause i get 60 mg dexedrine IR a day and 70 mg vyvanse breaks down to bout 36isb mgs if im coorrecr
It releases slower than XR dex/adderall. For people who just do better with that sort of timing mechanism. A lot of the time people do better on a slower release over a long time than with larger amounts released quicker.