Preparation of 99mTc-levetiracetam intranasal microemulsion as the first radiotracer for SPECT imaging of the Synaptic Vesicle Protein SV2A

Abstract

Selective receptors imaging using gamma emitting radiopharmaceuticals allows accurate diagnosis and follow up of many brain related disorders. Levetiracetam, a selective SV2A receptor antiepileptic, was successfully radiolabeled using ^99mTc. Different conditions affecting the labelling process were studied and optimum radiochemical yield of 89.8% was obtained. ^99mTc-levetiracetam was effectively formulated and characterized as microemulsion with particle size of 16.34 ± 5.58 nm and polydispersity index of 0.382 ± 0.05. Parallel biodistribution studies were performed comparing brain targeting efficiency of I.V ^99mTc-levetiracetam solution, I.N ^99mTc-levetiracetam solution and I.N ^99mTc-levetiracetam microemulsion. Brain radioactivity uptake and brain/blood uptake ratio for I.N ^99mTc-levetiracetam microemulsion were higher than the other two routes at all time intervals. Such results present intranasal ^99mTc-levetiracetam microemulsion as the first SPECT tracer for imaging SV2A receptor.

Keywords: Levetiracetam; Microemulsion; Radiopharmaceuticals; Receptor imaging.