“Stable Doses” and Tolerance for Medication – How Does It Work?


I’d like to know specifically about stimulants but any general knowledge is great! I’m currently a couple weeks into taking Vyvanse for my ADHD and was wondering about dosages.

You’re expected to gradually increase dosages until you end up at the one that continuously works best for you. I’m aware that tolerance increases and effects dim with prolonged use. Scientifically, how are patients able to get to their “stable dose”, still experiencing the effects they need, without an eventual increase in tolerance that inhibits effects?


In: 4

To understand the process you need to keep a few things in mind:

* Your liver is responsible for “processing” (and neutralizing) any and all chemicals in your blood. There are many blood vessels around the stomach and intestines, so things go into the blood and straight to the liver; liver processes nutrients and chemicals at the top rate that it can handle, and dumps the results back in the blood. Then kidneys are responsible for taking (processed) toxins out of the blood.

* So when you take your pills, the concentration of Vyvanse in the blood spikes, and then the liver works at it to reduce it. It’s not a linear decay, it’s an [exponential decay](https://media.drugs.com/wp-content/uploads/2019/03/drug-half-life-graph.png).

* So what you need to do is take pills often enough for the “average” concentration to be at the level required, which means the actual concentration of medication will look like the [bottom graph here](https://ars.els-cdn.com/content/image/1-s2.0-S0920121116302613-gr1.jpg). Note how the concentration increases until it reaches a stable up-and-down behavior after a few days.

Tolerance depends on the “target cells” (in your case, neurons) “getting used” to the medication to where it no longer affects the cell. The process is different for different medications, has to do with how the chemical gets *into* the cell (how it’s transported across the cell wall) and then also what effect it has *inside* the cell. And I don’t know any of that info, sorry, it’s a bit beyond my understanding.

I do have [a link for some info](https://www.ncbi.nlm.nih.gov/books/NBK548941/) on the (load/toxicity) the medication places on your liver as it processes it, though.