Clonidine is a pharmaceutical drug used to treat a wide variety of conditions including hypertension, ADHD, insomnia, chemical withdrawal, and anxiety. Clonidine is often prescribed in combination with other drugs, depending on the clinical condition. This stable-labeled internal standard is suited for quantitation of clonidine levels in urine, serum, or plasma by LC/MS or GC/MS for urine drug testing, clinical toxicology, forensic analysis, or isotope dilution methods.