Rasagiline-13C3is intended for use as an internal standard for the quantification of rasagiline by GC- or LC-MS. Rasagiline is an inhibitor of monoamine oxidase B (MAO-B; IC50= 4.43 nM for the rat brain enzyme).1It is selective for MAO-B over MAO-A (IC50= 412 nM for the rat brain enzyme). It inhibits serum and NGF withdrawal-induced apoptosis of PC12 cells when used at concentrations ranging from 0.01 to 100 μM.2Rasagiline inhibits rat brain MAO-Bin vivo(ED50= 0.1 mg/kg).1It reduces cerebral edema in a mouse model of traumatic brain injury.2Rasagiline (0.1 mg/kg) reduces cortical and hippocampal levels of full-length and soluble amyloid precursor protein (APP) in rats and mice. It also reduces α-synuclein-induced substantia nigral neuron loss and improves motor dysfunction in a mouse model of Parkinson's disease.3Formulations containing rasagiline have been used in the treatment of Parkinson's disease.