This stable-labeled internal standard is suitable for quantitation of hydroxybupropion levels in urine, serum, or plasma by LC/MS or GC/MS for urine drug testing, clinical toxicology, forensic analysis, or isotope dilution methods. (±)-Hydroxybupropion is a major bupropion metabolie in urine. Bupropion is a pharmaceutical used as an antidepressant and a smoking cessation drug sold under the trade name Wellbutrin and Zyban.