Yeah, Adderall is a mixture of dextroamphetamine and levoamphetamine (which are the right- and left-handed molecules of amphetamine).

Vyvanse is dextroamphetamine molecule attached to an extra Lysine amino-acid molecule. In this bound state, it doesn't really do anything in the body; the body will, however, metabolize it and break it into its constituent parts of dextroamphetamine and lysine.

Adderall XR (and many extended release medications) rely on adding a coating that will take the body a longer time to break down before releasing the medication, which results in an initial dose with a secondary dose being released later.

Vyvanse is much different in that regard, as the body is continuously breaking the double-molecule medication apart, providing a steady release of the medication throughout the day instead of just two (or, in the case of newer extra-extended release version, three) "bursts".

Is there any alternatives that still work well for you?

Due to the shortage, I switched to Vyvanse after ~18 years of Adderall. I was skeptical, but I figured I'd rather have a medication that worked okay rather than no medication and I could always go back once the shortage subsided. But I've actually been really happy with Vyvanse.

I had been on 50mg IR (taken in 10mg increments throughout the day) to get a smooth rise, level effects throughout the day, and to prevent a hard crash in the evening. And 50mg Vyvanse pretty closely matches that effect, but just with a little slower onset.

At this point, even if the pharmacies were overflowing with Adderall, I wouldn't switch back. The only downside to it is that I used to be able to tailor my doses to last longer in the evening when I was expecting the need to have more focus later than normal by pushing back my latter doses. But this happens less frequently so it isn't much of an issue.

Assuming your insurance covers it, I would say it's definitely worth giving Vyvanse a try. Worst case scenario, you'll have a medication that isn't as effective—but at least you'll have medication.

Your car's engine has a temperature sensor on the air intake, because it needs a certain fuel-to-oxygen ratio in the cylinder to ensure all of the fuel is ignited. Cold air is denser, so more fuel is injected in colder weather for the same volume of air. While accelerating, it won't make much of a difference, but it would lead to decreased fuel mileage due to more fuel used while idling and coasting.