What do zanaflex 4mg show up in your sistem as?

Zanaflex (tizanidine) shows up in your system as tizanidine and its metabolites (none of which are active). Tizanidine is extensively metabolized,
with the two major metabolites of tizanidine having been
identified as DS-200-717 (metabolite 3, guanidine, [(5-chloro-4-(2-
imidazolin-4-on-2-ylamino)-2,1,3-benzothiazdiazole] and DS-201-
341 (metabolite 4, amide, [5-chloro-4-(guanidino)-2,1,3-benzothiazdiazole]).

http://dmd.aspetjournals.org/content/27/2/201.full.pdf

Pharmacokinetics, Metabolism and Excretion

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Tizanidine has linear pharmacokinetics over a dose of 1 mg to 20 mg. Tizanidine has a half-life of approximately 2.5 hours (CV = 33%). Approximately 95% of an administered dose is metabolized. The primary cytochrome P450 isoenzyme involved in tizanidine metabolism is CYP1A2. Tizanidine metabolites are not known to be active; their half-lives range from 20 to 40 hours.

http://www.drugs.com/pro/zanaflex.html