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Objective: Clonazepam (CP) is a potent long-acting nitrobenzodiazepine derivative that could be used for targeting peripheral benzodiazepine receptors. Phospholipid magnesome is a new vesicular nanosystem recently developed for brain targeting. Improving the uptake of 131 I-CP to the brain might be effective for the diagnosis and/or radiotherapy of certain brain diseases and/or tumors., Methods: CP was radiolabeled with 131 I using direct electrophilic substitution reaction. Quality control of 131 I-CP was performed using different techniques. Different formulas of 131 I-CP were prepared and characterized according to particle size and polydispersity index. The structural features of the optimized formula were then interpreted using transmission electron microscopy and scanning electron microscopy, whereas pharmacokinetic and in vivo behaviors were estimated using the intravenous and intranasal delivery routes., Results: The heart and blood demonstrated lower uptake of 131 I-CP, which inevitably decreased the nontarget effects of radioiodine. Intranasally administered 131 I-CP-loaded magnesomes (INMg) had noticeably higher brain uptake (7.1 ± 0.09%ID/g) with rapid onset of action within 5 min and effective pharmacokinetic behavior. INMg had a drug targeting efficiency and nose-to-brain direct transport percentage of 121.1% and 94.6%, respectively as well as a relative bioavailability of 441.04 ± 75.5%., Conclusion: The present study showed that 131 I-CP-loaded magnesomes can be a beneficial brain-targeting approach for improving the diagnosis and/or radiotherapy of certain brain diseases., (Copyright © 2021. Published by Elsevier B.V.)

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 99m Tc. Different conditions affecting the labelling process were studied and optimum radiochemical yield of 89.8% was obtained. 99m Tc-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 99m Tc-levetiracetam solution, I.N 99m Tc-levetiracetam solution and I.N 99m Tc-levetiracetam microemulsion. Brain radioactivity uptake and brain/blood uptake ratio for I.N 99m Tc-levetiracetam microemulsion were higher than the other two routes at all time intervals. Such results present intranasal 99m Tc-levetiracetam microemulsion as the first SPECT tracer for imaging SV2A receptor., (Copyright © 2018 Elsevier B.V. All rights reserved.)