actually, cyclobenzaprine is closely related to tricyclic antidepressants.
cyclobenzaprine HCl (Flexeril) is NOT recreationally abusable in any real way. it just makes you tired. "muscle relaxant" does sound like a fun category, but it's not. trust me.
learn to recognize a typical pharmaceutical tablet in the future because there's a fair amount of drugs being sold as E that OBVIOUSLY aren't.
a typical E will be round, could be white or colored, and will have a crude logo stamped in it. they're usually small and thick, relative to a commercially prepared tablet.
a commercial medicinal drug could really look like anything, but there's a few general rules things that might help you.
real E's are usually round: pharmaceuticals are often round too but they come in all kinds of shapes. you should pretty much ignore any e that isn't round; look at dancesafe and you'll see that e's that aren't round are quite a bit more likely to be DXM or something bad. a lot of pharms are strange shapes like pentagons or something, and you can ignore those if you want e.
look at the press: the logo will pretty much tell you if it's a pharm or not. Roche and Merck-Frosst don't put mitsu logos on their pills. if there's any writing on a pharm, it'll be small, clear and precise. there may be a manufacturer code, like CL or sometimes the name like NOVO. codes with a number like the pill you described are really common. really, that should be enough.
colors: pharms aren't always white, but they tend to be. if they're not, they tend to be a nice, calm institutional color like beige or peach. there *are* tabs of all kinds of colors, even blue (e.g. Adderal) and green (e.g. Rivotril, the canadian version of Klonopin).
size: if it's smaller than an E, obviously you don't want it. a general rule for judging pharms is that small pills are far more likely to be fun. if it's a big 500 mg tab, it's probably some antibiotic.
it is obviously never worth it to buy a pharm as E, even if you know it's fun.