Ok, since you are from Syndey, I am going to assume that by "speed" you mean amphetamine (usually speed=meth in the USA).
First off, you should know that serotonin (the main chemical in your brain involved with MDMA use) is quite different from dopamine (the main chemical for amphetamine and methamphetine alike). It takes a while for you brain to rebuild its serotonin levels because of various rate-limiting steps in serotonin production, but this is NOT the case for dopamine.
This means that although you can take amino acids (such as l-tyrosine or DLPA, 1000 mg prior, 2 x 1000 mg the day after, in two doses) to boost your dopamine production, it won't make that much of a difference as your brain will rebuild its dopamine levels fairly quickly anyways.
What is much more important with amphetamine and methamphetamine use is trying to combat the oxidative (i.e., "bleaching") effect on the brain. This can be done with a good old multivitamin (double dose it, both before and after) and powerful antioxidants like alpha-lipoic acid (take 500 mg before,1000 mg right when you do your drugs, 2000mg right as you are coming down, and 1000 mg a day for two days after. I also can't emphasize enough the importance of drinking enough water. This will help with the damage, will help with the next day, and will help flush the toxins out of your body sooner.
