A large reason methylphenidate was developed was to come up with a drug that would help treat ADHD (ADHD has been around a long time under many different names) but that would have fewer side effects than amphetamines.
Methylphenidate has similar pharmacologic actions as amphetamines and both are apart of a large group of drugs called substituted phenethylamines. Methylphenidate was derived from amphetamine however it is distinctly different and NOT classified as an amphetamine or a substituted amphetamine, it is a piperidine. Actually the chemical structure of methylphenidate is more similar to cocaine than it is to amphetamine. Cocaine, methylphenidate, and amphetamines all act on the dopamine system however cocaine and methylphenidate have significantly different actions compared to amphetamine but all three drugs increase dopamine. So basically methylphenidate and amphetamine do similar things but they do it differently.
You should probably talk to your doctor about your "crash." You may need to make a different form of methylphenidate (Concerta is the best long acting form). Or you may do well by taking a dose of instant release methylphenidate like Ritalin when the Metadate starts to wear off. Also, once you start to crash, often having a soda like Mountain Dew or anything is a modestly high level of caffeine (ie less than an energy drink but more than most sodas) is very helpful.
Also most likely after a few days or weeks the crash won't be as bad (it may very well go away) and the effect the drug has on you won't be as extreme but it should still allow you to focus. Aside from things simply getting better on their own other forms of methylphenidate or even Focalin or Focalin XR (dexmethylphenidate) are good options.
Unfortunately depression and fatigue are common effects when people come down off of stimulants. Amphetamines tend to have a worse crash but it is always possible that you would do better on an amphetamine like Adderall or Dexedrine.
Give it some time, if it really bothers you call your doctor, and if needed explore other options.
M.D., C.M. psychiatry, internal medicine (Québec)
Hons. BSc in pharmacology