I just addressed a similar question:
http://www.bluelight.org/vb/threads...while-on-amphetamines?p=13157300#post13157300
But I can sum up...
First an aside...
My biased opinion is that Ritalin is poison. There are so many generic forms out there because of its age (I think it was approved in the 50's) so there are so many dirty cheap forms of it. Even brand name Ritalin isn't produced by the original manufacturer (I think).
I have heard many people say that it is the easiest one to build tolerance to and I think that is spot on. It is essentially cocaine in a pill but stronger.
I think many doctors prescribe it because it has a reputation of being "safer" than amphetamine salts... I suppose it does have a less neurotoxic profile in the short term, but it will invariably lead to addictive hell for most.
So back to the question:
The first cause of tolerance to stims is indirect, through glutamate, the excitatory neurotransmitter.
Chronic stimulant use leads to higher than average levels of glutamate released from one neuron to another. The main receptors for glutamate on the receiving neuron are NMDA and AMPA receptors.
NMDA receptors, everyones favorite, actually play a very small role in the grand scheme of things. Before tolerance is built, at baseline, NMDA receptors reject the released glutamate from binding to it and entering its neuron. So all of the glutamate traffic bombards the AMPA receptor. The AMPA receptor is like that girl that surprisingly requires no effort to get inside of. Everybody gets in. Once enough glutamate gets into the receiving neuron, more than it can handle, it starts to misbehave. This is called a depolarized neuron. In this state, the NMDA receptor now becomes open for glutamate to enter and more importantly, calcium. Calcium is the main cause of tolerance and dependance. It wreaks havoc inside the neuron further by making it even easier for glutamate to enter through the AMPA receptor; activating AMPA receptor stores that are resting inside the neuron and bringing them to the surface of the synapse so they can receive more glutamate; AND sending signals back to the sending neuron asking for more glutamate! So this cycle continues and more and more glutamate is required to elicit a response until the glutamate stores are not enough to keep up with the out of control demands of the depolarized neuron. No matter how much of a stim you take it won't be enough to ellicit a response from the depolarized neuron. Even when you withdrawal from the stimulant, the adaptations that have occurred to the receiving neuron remain in place causing you to crave the drug just to feel relatively normal.
The second way is the much more obvious of the two... Downregulation/Subsensitivity of the dopamine D2 high receptors. Ill go on a limb and say that in order for this to be the main cause of tolerance you have to be taking very high doses for a very long time. I think this is the less common cause of the two.
And of course there are most likely hundreds of other mechanisms at play that we have no or not enough current knowledge of. (E.G. genetic adaptations)
How to treat?
I think for first time stimulant users there are more options. In this case the main thing you want to do is stop Calcium from entering the post synaptic neuron. You may be tempted to buy into the magnesium argument or maybe some other over the counter natural life hack "miracle". Don't. Magnesium supplementation is complicated, unpredictable. Even if you bypass the absorption issues by I.V. or skin absorbtion than you have the blood brain barrier to worry about. You have to worry the brand and type of magnesium is legit. You have to worry about how your body will metabolize magnesium vs others. Magnesium is already in the body. You need something foreign.
For first timers I would recommend:
Memantine: Its cliche and I don't really like it but it might really work for FIRST timers. Memantine, among other things, is an antagonist at the NMDA receptor magnesium binding site. This means it functions as synthetic magnesium in a way. It has been studied, we know it binds, etc.. This binding site is responsible for allowing calcium to enter the neuron. While a depolarized neuron is able to brush off a natural mineral like magnesium, it can't tell this supercharged synthesized chemical what to do. Memantine has an extremely long half life (40-80 hours) and is bound for the majority of that time. This should effectively limit calcium entry into the post synaptic neuron.
I have tried memantine and I didn't like it much. Of course I had been using stims previous to it. Its ok though. You have to put up with feeling slightly retarded for about a week because of its action at other sites (nACH antagonist). After that you don't really notice anything until you get into the 20 or 30 mg range. In that range it literally fries any worry you have out of your brain. Wouldn't recommend long term. I would stay in the 10 mg range max.
Other NMDA antagonists: There are not many of them and I am not sure if any of them are specific to the magnesium binding site but it might be worth a look.
AMPA antagonists: These have a reputation for making you dumb. Like catatonic slobber all over yourself dumb. However, maybe the stimulant would offset that? Not sure. Topamax is the first one that comes to mind, there are others. It would be tougher to guarantee the dose you are taking is truly blocking calcium from entering the cell compared to memantine.
Calcium Channel Blockers: I would really like to get my hands on a lot of these. FDA approved for high blood pressure they have been used to treat most every psychiatric disorder. Schizophrenia, depression, anxiety, bi-polar, etc... Probably because these are all on the same spectrum.
These do what they say and are effective. If you search around you will find that to be true. Of course, if calcium is blocked the neuron can't depolarize and you won't get tolerance for a very long time.
What if I have tolerance?
This is more difficult, and maybe impossible, depending, to fix.
What needs to be done:
AMPA receptor down regulation.
Break the calcium pre-postsynaptic feedback loop.
Desensitize Dopamine D2 High receptors
These are all interrelated and its hard to know if fixing one will fix the others.
AMPA receptors behave in a typical fashion aka when agonized they downregulate. When antagonized they upregulate.
If you already have tolerance chances are you already have too many AMPA receptors on the synaptic surfaces. So while a temporary fix might be to
antagonize them I could see that as big problem down the road. You might end up with more than you started and really be in trouble. I think agonizing is the way to go. I have used Tianeptine with good effect. The vast majority of Nootropics are AMPA agonists (phenylpiracetam, sunifram) to name a few. Worst case you feel more stimulated and anxious in the short term but things might start to settle back into balance long term.
Breaking the calcium channel feedback loop is a matter of getting a hold of a supply of calcium channel antagonists which might be difficult. There are almost definitely other indirect ways of doing this I just don't know.
Desenstizing D2 high receptors is scary for a couple reasons. First off with tolerance you probably have at least a small D2 receptor subsentivity which is one of the main pathological features of schizophrenia (albeit schizophrenics present with extremely high d2 subsensitivity). This is why with tolerance you no longer feel those fuzzy tickling feelings in you're frontal lobe and high level executive regions of the brain. More likely you feel slight stimulation and anxiety stemming from a more centralized part of your brain (but everyones different). When you have this subsensitivity dopamine never gets projected out to those high level functioning areas, it is all metabolized and limited to midbrain structures where all of the subsensitive receptors are.
Depending on have brave you are this is where an antipsychotic would come in handy as most function primarily as a D2 receptor antagonist.
Most of these drugs are useless tools that are essentially a chemical lobotomy. They literally shrink your brain by 10% in the first year of use.
However that is mostly limited to the old school drugs like Haloperidol, Thoriazine, etc.. No one should ever take those. There is a movement going on in the last 10 years or so however and it is centered a round a few solid non destructive drugs. These are Quetiapine, Aripiprazole (abilify) and the brand new (approved last week new) brexpiprazole. Quetiapine has very weak d2 binding or the razole drugs which are d2 partial agonists (aka they antagonize d2 in certain midbrain structures and agonize it elsewhere promoting a healthy flow of dopamine). For the razole drugs, you have to really shell out though as a months supply is upwards of 1k.
