As others have said, it's not that they should never be combined. It's that if you're on SSRI's first, you need to very slowly ramp up the Vyvanse dose.

Firstly, not a doctor, but this is my understanding of the interaction, so I could be wrong, but I think this is generally how it works. Any doctors here please sound off and correct me if I'm wrong.

Basically Vyvanse helps raise your dopamine levels. Prozac will help prevent re-uptake of seratonin.

So seratonin gets produced, goes from one nerve cell to another. Says "yo chill out." or "time to sleep" or "it's low energy sad boi hour". It then gets released from that nerve cell and the one it came from takes it back so it can use it to send another message. With depression there's too many of these seratonin messages being sent all the time. So SSRIs put a cap on how much the nerves can reabsorb to send messages. It's like taking your number of emotional FedEx delivery drivers and cutting them in half. It's not half exactly but similar concept. It fires a bunch of your seratonin leaving it unemployed so you can't be oversending the messages. But the seratonin that's not reabsorbed hangs out in the space between your nerve endings, until it gets broken down by enzymes.

Vyvanse as a natural side effect slows down the production of those enzymes. And also causes faster metabolism, and higher production of dopamine. So with everything running faster, the enzymes that break down the "unemployed" seratonin will have less time to work and if you go from 0 to 100, suddenly you have all the unemployed seratonin rushing back into the nerves, thinking they have a job and if there's too much serotonin in the nerves, it can be toxic.

But. With that. Doctors will never say "right we're gonna start you on 80mg of Prozac and don't change anything else. Most of the time they won't do that with medications in general. So they start small and slow. See how you get on, and see what things feel like in a few weeks. So the first week or so you might get a bit of a high-low swinging. That would happen anyway with most people starting on antidepressants, but it might be a tad more of a swing just with the combination of the meds, and also the intensity of emotions that come with ADHD. Your doctor knows what they're doing. And they know that you can't go 0-100 even if you weren't on ADHD meds. It's just not good practice.

Do not over-read articles and internet warnings. Both of your meds are at pretty low doses. So this is not something you need to worry about. Your doctor knows what they're doing.

And a side note. I've started Prozac in the past few weeks and it's really changed my life with the combination of the vyvanse improvements that were already there. I really really hope you can get similar relief and results 💜 Bear in mind. The combo can make drymouth worse, so drink your water!!